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A fingerprint is an impression left by the
friction ridge The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided ...
s of a human
finger A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers ( Pentadactyly). Chamber ...
. The recovery of partial fingerprints from a crime scene is an important method of
forensic science Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal ...
. Moisture and grease on a finger result in fingerprints on surfaces such as glass or metal. Deliberate impressions of entire fingerprints can be obtained by ink or other substances transferred from the peaks of friction ridges on the skin to a smooth surface such as paper. Fingerprint records normally contain impressions from the pad on the last joint of fingers and thumbs, though fingerprint cards also typically record portions of lower joint areas of the fingers. Human fingerprints are detailed, nearly unique, difficult to alter, and durable over the life of an individual, making them suitable as long-term markers of human identity. They may be employed by police or other authorities to identify individuals who wish to conceal their identity, or to identify people who are incapacitated or deceased and thus unable to identify themselves, as in the aftermath of a natural disaster. Their use as evidence has been challenged by academics, judges and the media. There are no uniform standards for point-counting methods, and academics have argued that the error rate in matching fingerprints has not been adequately studied and that fingerprint evidence has no secure
statistical Statistics (from German: '' Statistik'', "description of a state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industr ...
foundation. Research has been conducted into whether experts can objectively focus on feature information in fingerprints without being misled by extraneous information, such as context.Dror, I.E., Charlton, D. and Péron, A.E. (2006)
Contextual information renders experts vulnerable to making erroneous identifications
, ''Forensic Science International'', Vol. 156, Iss. 1, pp. 74–78.


Biology

Fingerprints are impressions left on surfaces by the friction ridges on the finger of a human. The matching of two fingerprints is among the most widely used and most reliable
biometric Biometrics are body measurements and calculations related to human characteristics. Biometric authentication (or realistic authentication) is used in computer science as a form of identification and access control. It is also used to identify in ...
techniques. Fingerprint matching considers only the obvious features of a fingerprint. The composition of fingerprints consists of water (95%-99%), as well as organic and inorganic constituents. The organic component is made up of amino acids, proteins, glucose, lactase, urea, pyruvate, fatty acids and sterols. Inorganic ions such as chloride, sodium, potassium and iron are also present. Other contaminants such as oils found in cosmetics, drugs and their metabolites and food residues may be found in fingerprint residues. A friction ridge is a raised portion of the
epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rel ...
on the digits (fingers and toes), the palm of the hand or the sole of the foot, consisting of one or more connected ridge units of friction ridge skin. These are sometimes known as "epidermal ridges" which are caused by the underlying interface between the dermal papillae of the dermis and the interpapillary (rete) pegs of the epidermis. These epidermal ridges serve to amplify
vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, su ...
s triggered, for example, when fingertips brush across an uneven surface, better transmitting the signals to
sensory nerve A sensory nerve, or afferent nerve, is a general anatomic term for a nerve which contains predominantly somatic afferent nerve fibers. Afferent nerve fibers in a sensory nerve carry sensory information toward the central nervous system (CNS) fro ...
s involved in fine texture perception. These ridges may also assist in gripping rough surfaces and may improve surface contact in wet conditions.


Genetics

Consensus within the scientific community suggests that the dermatoglyphic patterns on fingertips are hereditary. The fingerprint patterns between
monozygotic Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...
twins have been shown to be very similar, whereas dizygotic twins have considerably less similarity. Significant
heritability Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of ''variation'' in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of her ...
has been identified for 12 dermatoglyphic characteristics. Current models of dermatoglyphic trait inheritance suggest
Mendelian Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularize ...
transmission with additional effects from either additive or dominant major genes. Whereas genes determine the general characteristics of patterns and their type, the presence of environmental factors result in the slight differentiation of each fingerprint. However, the relative influences of genetic and environmental effects on fingerprint patterns are generally unclear. One study has suggested that roughly 5% of the total variability is due to small environmental effects, although this was only performed using total ridge count as a metric. Several models of finger ridge formation mechanisms that lead to the vast diversity of fingerprints have been proposed. One model suggests that a buckling instability in the basal cell layer of the fetal
epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rel ...
is responsible for developing epidermal ridges. Additionally, blood vessels and nerves may also serve a role in the formation of ridge configurations. Another model indicates that changes in amniotic fluid surrounding each developing finger within the uterus cause corresponding cells on each fingerprint to grow in different microenvironments. For a given individual, these various factors affect each finger differently preventing two fingerprints from being identical while still retaining similar patterns. It is important to note that the determination of fingerprint inheritance is made difficult by the vast diversity of
phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...
s. Classification of a specific pattern is often subjective (lack of consensus on the most appropriate characteristic to measure quantitatively) which complicates analysis of dermatoglyphic patterns. Several modes of inheritance have been suggested and observed for various fingerprint patterns. Total fingerprint ridge count, a commonly used metric of fingerprint pattern size, has been suggested to have a
polygenic A polygene is a member of a group of non- epistatic genes that interact additively to influence a phenotypic trait, thus contributing to multiple-gene inheritance (polygenic inheritance, multigenic inheritance, quantitative inheritance), a type of ...
mode of inheritance and is influenced by multiple additive genes. This hypothesis has been challenged by other research, however, which indicates that ridge counts on individual fingers are genetically independent and lack evidence to support the existence of additive genes influencing pattern formation. Another mode of fingerprint pattern inheritance suggests that the arch pattern on the thumb and on other fingers are inherited as an autosomal dominant trait. Further research on the arch pattern has suggested that a major gene or multifactorial inheritance is responsible for arch pattern heritability. A separate model for the development of the whorl pattern indicates that a single gene or group of linked genes contributes to its inheritance. Furthermore, inheritance of the whorl pattern does not appear to be symmetric in that the pattern is seemingly randomly distributed among the ten fingers of a given individual. In general, comparison of fingerprint patterns between left and right hands suggests an asymmetry in the effects of genes on fingerprint patterns, although this observation requires further analysis. In addition to proposed models of inheritance, specific genes have been implicated as factors in fingertip pattern formation (their exact mechanism of influencing patterns is still under research). Multivariate linkage analysis of finger ridge counts on individual fingers revealed linkage to
chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins ar ...
5q14.1 specifically for the ring, index, and middle fingers. In mice, variants in the gene EVI1 were correlated with dermatoglyphic patterns. EVI1 expression in humans does not directly influence fingerprint patterns but does affect limb and digit formation which in turn may play a role in influencing fingerprint patterns. Genome-wide association studies found
single nucleotide polymorphisms In genetics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a sufficiently lar ...
within the gene ADAMTS9-AS2 on 3p14.1, which appeared to have an influence on the whorl pattern on all digits. This gene encodes
antisense RNA Antisense RNA (asRNA), also referred to as antisense transcript, natural antisense transcript (NAT) or antisense oligonucleotide, is a single stranded RNA that is complementary to a protein coding messenger RNA (mRNA) with which it hybridizes, and ...
which may inhibit ADAMTS9, which is expressed in the skin. A model of how genetic variants of ADAMTS9-AS2 directly influence whorl development has not yet been proposed.


Classification systems

Before computerization, manual filing systems were used in large fingerprint repositories. A fingerprint classification system groups fingerprints according to their characteristics and therefore helps in the matching of a fingerprint against a large database of fingerprints. A query fingerprint that needs to be matched can therefore be compared with a subset of fingerprints in an existing
database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases ...
. Early classification systems were based on the general ridge patterns, including the presence or absence of circular patterns, of several or all fingers. This allowed the filing and retrieval of paper records in large collections based on friction ridge patterns alone. The most popular systems used the pattern class of each finger to form a numeric key to assist lookup in a filing system. Fingerprint classification systems included the Roscher System, the Juan Vucetich System and the Henry Classification System. The Roscher System was developed in Germany and implemented in both Germany and Japan. The Vucetich System was developed in
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...
and implemented throughout South America. The Henry Classification System was developed in India and implemented in most English-speaking countries. In the Henry Classification System there are three basic fingerprint patterns: loop, whorl, and arch, which constitute 60–65 percent, 30–35 percent, and 5 percent of all fingerprints respectively. There are also more complex classification systems that break down patterns even further, into plain arches or tented arches, and into loops that may be radial or ulnar, depending on the side of the hand toward which the tail points. Ulnar loops start on the pinky-side of the finger, the side closer to the
ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
, the lower arm bone. Radial loops start on the thumb-side of the finger, the side closer to the
radius In classical geometry, a radius (plural, : radii) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', ...
. Whorls may also have sub-group classifications including plain whorls, accidental whorls, double loop whorls, peacock's eye, composite, and central pocket loop whorls. The system used by most experts, although complex, is similar to the Henry Classification System. It consists of five
fraction A fraction (from la, fractus, "broken") represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight ...
s, in which ''R'' stands for right, ''L'' for left, ''i'' for index finger, ''m'' for middle finger, ''t'' for thumb, ''r'' for ring finger and ''p''(pinky) for little finger. The fractions are as follows:
Ri/Rt + Rr/Rm + Lt/Rp + Lm/Li + Lp/Lr
The numbers assigned to each print are based on whether or not they are whorls. A whorl in the first fraction is given a 16, the second an 8, the third a 4, the fourth a 2, and 0 to the last fraction. Arches and loops are assigned values of 0. Lastly, the numbers in the numerator and denominator are added up, using the scheme:
(Ri + Rr + Lt + Lm + Lp)/(Rt + Rm + Rp + Li + Lr)
A 1 is added to both top and bottom, to exclude any possibility of division by zero. For example, if the right ring finger and the left index finger have whorls, the fraction used is:
0/0 + 8/0 + 0/0 + 0/2 + 0/0 + 1/1
The resulting
calculation A calculation is a deliberate mathematical process that transforms one or more inputs into one or more outputs or ''results''. The term is used in a variety of senses, from the very definite arithmetical calculation of using an algorithm, to t ...
is:
(0 + 8 + 0 + 0 + 0 + 1)/(0 + 0 + 0 + 2 + 0 + 1) = 9/3 = 3


Fingerprint identification

Fingerprint identification, known as dactyloscopy, or hand print identification, is the process of comparing two instances of friction ridge skin impressions (see Minutiae), from human fingers or toes, or even the palm of the hand or sole of the foot, to determine whether these impressions could have come from the same individual. The flexibility of friction ridge skin means that no two finger or palm prints are ever exactly alike in every detail; even two impressions recorded immediately after each other from the same hand may be slightly different. Fingerprint identification, also referred to as individualization, involves an expert, or an expert computer system operating under threshold scoring rules, determining whether two friction ridge impressions are likely to have originated from the same finger or palm (or toe or sole). An intentional recording of friction ridges is usually made with black printer's ink rolled across a contrasting white background, typically a white card. Friction ridges can also be recorded digitally, usually on a glass plate, using a technique called Live Scan. A "latent print" is the chance recording of friction ridges deposited on the surface of an object or a wall. Latent prints are invisible to the naked eye, whereas "patent prints" or "plastic prints" are viewable with the unaided eye. Latent prints are often fragmentary and require the use of chemical methods, powder, or alternative light sources in order to be made clear. Sometimes an ordinary bright flashlight will make a latent print visible. When friction ridges come into contact with a surface that will take a print, material that is on the friction ridges such as
perspiration Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distr ...
, oil, grease, ink, or blood, will be transferred to the surface. Factors which affect the quality of friction ridge impressions are numerous. Pliability of the skin, deposition pressure, slippage, the material from which the surface is made, the roughness of the surface, and the substance deposited are just some of the various factors which can cause a latent print to appear differently from any known recording of the same friction ridges. Indeed, the conditions surrounding every instance of friction ridge deposition are unique and never duplicated. For these reasons, fingerprint examiners are required to undergo extensive training. The scientific study of fingerprints is called dermatoglyphics.


Fingerprinting techniques


Exemplar

Exemplar prints, or known prints, is the name given to fingerprints deliberately collected from a subject, whether for purposes of enrollment in a system or when under arrest for a suspected criminal offense. During criminal arrests, a set of exemplar prints will normally include one print taken from each finger that has been rolled from one edge of the nail to the other, plain (or slap) impressions of each of the four fingers of each hand, and plain impressions of each thumb. Exemplar prints can be collected using live scan or by using ink on paper cards.


Latent

In
forensic science Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal ...
a partial fingerprint lifted from a surface, is called a ''latent fringerprint''. Moisture and grease on fingers result in latent fingerprints on surfaces such as glass. But because they are not clearly visible, their detection may require chemical development through powder dusting, the spraying of ninhydrin,
iodine Iodine is a chemical element with the Symbol (chemistry), symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , ...
fuming, or soaking in
silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...
. Depending on the surface or the material on which a latent fingerprint has been found, different methods of chemical development must be used. Forensic scientists use different techniques for
porous Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
surfaces, such as paper, and nonporous surfaces, such as glass, metal or plastic. Nonporous surfaces require the dusting process, where fine powder and a brush are used, followed by the application of transparent tape to lift the latent fingerprint off the surface. While the police often describe all partial fingerprints found at a crime scene as latent prints, forensic scientists call partial fingerprints that are readily visible ''patent prints''. Chocolate, toner, paint or ink on fingers will result in patent fingerprints. Latent fingerprints impressions that are found on soft material, such as soap, cement or plaster, are called ''plastic prints'' by forensic scientists.


Capture and detection


Live scan devices

Fingerprint image acquisition is considered to be the most critical step in an automated fingerprint authentication system, as it determines the final fingerprint image quality, which has a drastic effect on the overall system performance. There are different types of fingerprint readers on the market, but the basic idea behind each is to measure the physical difference between ridges and valleys. All the proposed methods can be grouped into two major families: solid-state fingerprint readers and optical fingerprint readers. The procedure for capturing a fingerprint using a sensor consists of rolling or touching with the finger onto a sensing area, which according to the physical principle in use (optical, ultrasonic, capacitive, or thermalsee ) captures the difference between valleys and ridges. When a finger touches or rolls onto a surface, the elastic skin deforms. The quantity and direction of the pressure applied by the user, the skin conditions and the projection of an irregular 3D object (the finger) onto a 2D flat plane introduce distortions, noise, and inconsistencies in the captured fingerprint image. These problems result in inconsistent and non-uniform irregularities in the image. During each acquisition, therefore, the results of the imaging are different and uncontrollable. The representation of the same fingerprint changes every time the finger is placed on the sensor plate, increasing the complexity of any attempt to match fingerprints, impairing the system performance and consequently, limiting the widespread use of this
biometric Biometrics are body measurements and calculations related to human characteristics. Biometric authentication (or realistic authentication) is used in computer science as a form of identification and access control. It is also used to identify in ...
technology. In order to overcome these problems, as of 2010, non-contact or touchless 3D fingerprint scanners have been developed. Acquiring detailed 3D information, 3D fingerprint scanners take a digital approach to the analog process of pressing or rolling the finger. By modelling the distance between neighboring points, the fingerprint can be imaged at a resolution high enough to record all the necessary detail.


Fingerprinting dead humans

The human skin itself, which is a regenerating organ until death, and environmental factors such as lotions and cosmetics, pose challenges when fingerprinting a human. Following the death of a human the skin dries and cools. Obtaining fingerprints from a dead human, to aid identification, is hindered by the fact that only the
coroner A coroner is a government or judicial official who is empowered to conduct or order an inquest into the manner or cause of death, and to investigate or confirm the identity of an unknown person who has been found dead within the coroner's jur ...
or medical examiner is allowed to examine the dead body. Fingerprints of dead humans may be obtained during an
autopsy An autopsy (post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of death or to evaluate any d ...
.


Latent fingerprint detection

In the 1930s criminal investigators in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
first discovered the existence of latent fingerprints on the surfaces of fabrics, most notably on the insides of gloves discarded by perpetrators. Since the late nineteenth century, fingerprint identification methods have been used by police agencies around the world to identify suspected criminals as well as the victims of crime. The basis of the traditional fingerprinting technique is simple. The skin on the palmar surface of the hands and feet forms ridges, so-called papillary ridges, in patterns that are unique to each individual and which do not change over time. Even identical twins (who share their DNA) do not have identical fingerprints. The best way to render latent fingerprints visible, so that they can be photographed, can be complex and may depend, for example, on the type of surfaces on which they have been left. It is generally necessary to use a "developer", usually a powder or chemical reagent, to produce a high degree of visual contrast between the ridge patterns and the surface on which a fingerprint has been deposited. Developing agents depend on the presence of organic materials or inorganic salts for their effectiveness, although the water deposited may also take a key role. Fingerprints are typically formed from the aqueous-based secretions of the eccrine glands of the fingers and palms with additional material from sebaceous glands primarily from the forehead. This latter contamination results from the common human behaviors of touching the face and hair. The resulting latent fingerprints consist usually of a substantial proportion of water with small traces of amino acids and chlorides mixed with a fatty, sebaceous component which contains a number of fatty acids and triglycerides. Detection of a small proportion of reactive organic substances such as urea and amino acids is far from easy. Fingerprints at a crime scene may be detected by simple
powders A powder is a dry, bulk solid composed of many very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms ''powder'' and '' granular'' are sometimes used to disti ...
, or by chemicals applied ''
in situ ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
''. More complex techniques, usually involving chemicals, can be applied in specialist laboratories to appropriate articles removed from a crime scene. With advances in these more sophisticated techniques, some of the more advanced crime scene investigation services from around the world were, as of 2010, reporting that 50% or more of the fingerprints recovered from a crime scene had been identified as a result of laboratory-based techniques.


Forensic laboratories

Although there are hundreds of reported techniques for fingerprint detection, many of these are only of academic interest and there are only around 20 really effective methods which are currently in use in the more advanced fingerprint laboratories around the world. Some of these techniques, such as ninhydrin, diazafluorenone and vacuum metal deposition, show great sensitivity and are used operationally. Some fingerprint reagents are specific, for example ninhydrin or diazafluorenone reacting with amino acids. Others such as
ethyl cyanoacrylate Ethyl cyanoacrylate (ECA), a cyanoacrylate ester, is an ethyl ester of 2-cyano-2-propenoic acid. It is a colorless liquid with low viscosity and a faint sweet smell in pure form. It is the main component of cyanoacrylate glues and can be encount ...
polymerisation, work apparently by water-based catalysis and polymer growth. Vacuum metal deposition using gold and zinc has been shown to be non-specific, but can detect fat layers as thin as one molecule. More mundane methods, such as the application of fine powders, work by adhesion to sebaceous deposits and possibly aqueous deposits in the case of fresh fingerprints. The aqueous component of a fingerprint, whilst initially sometimes making up over 90% of the weight of the fingerprint, can evaporate quite quickly and may have mostly gone after 24 hours. Following work on the use of argon ion lasers for fingerprint detection, a wide range of fluorescence techniques have been introduced, primarily for the enhancement of chemically developed fingerprints; the inherent fluorescence of some latent fingerprints may also be detected. Fingerprints can for example be visualized in 3D and without chemicals by the use of infrared lasers. A comprehensive manual of the operational methods of fingerprint enhancement was last published by the UK Home Office Scientific Development Branch in 2013 and is used widely around the world. A technique proposed in 2007 aims to identify an individual's
ethnicity An ethnic group or an ethnicity is a grouping of people who identify with each other on the basis of shared attributes that distinguish them from other groups. Those attributes can include common sets of traditions, ancestry, language, history, ...
, sex, and dietary patterns.


Crime scene investigations

The application of the new scanning Kelvin probe (SKP) fingerprinting technique, which makes no physical contact with the fingerprint and does not require the use of developers, has the potential to allow fingerprints to be recorded whilst still leaving intact material that could subsequently be subjected to DNA analysis. A forensically usable prototype was under development at Swansea University during 2010, in research that was generating significant interest from the British Home Office and a number of different police forces across the UK, as well as internationally. The hope is that this instrument could eventually be manufactured in sufficiently large numbers to be widely used by forensic teams worldwide.


Detection of drug use

The secretions, skin oils and dead cells in a human fingerprint contain residues of various chemicals and their
metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, ...
s present in the body. These can be detected and used for forensic purposes. For example, the fingerprints of tobacco smokers contain traces of
cotinine Cotinine is an alkaloid found in tobacco and is also the predominant metabolite of nicotine. An anagram of the word "nicotine", it is used as a biomarker for exposure to tobacco smoke. Cotinine is currently being studied as a treatment for d ...
, a
nicotine Nicotine is a naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and '' Duboisia hopwoodii'') and is widely used recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is use ...
metabolite; they also contain traces of nicotine itself. Caution should be used, as its presence may be caused by mere contact of the finger with a tobacco product. By treating the fingerprint with gold
nanoparticle A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 10 ...
s with attached
cotinine Cotinine is an alkaloid found in tobacco and is also the predominant metabolite of nicotine. An anagram of the word "nicotine", it is used as a biomarker for exposure to tobacco smoke. Cotinine is currently being studied as a treatment for d ...
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of ...
, and then subsequently with a fluorescent agent attached to cotinine antibodies, the fingerprint of a smoker becomes fluorescent; non-smokers' fingerprints stay dark. The same approach, as of 2010, is being tested for use in identifying heavy
coffee Coffee is a drink prepared from roasted coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content. It is the most popular hot drink in the world. Seeds of ...
drinkers, cannabis smokers, and users of various other drugs.


Police force databases

Most American law enforcement agencies use Wavelet Scalar Quantization (WSQ), a
wavelet A wavelet is a wave-like oscillation with an amplitude that begins at zero, increases or decreases, and then returns to zero one or more times. Wavelets are termed a "brief oscillation". A taxonomy of wavelets has been established, based on the num ...
-based system for efficient storage of compressed fingerprint images at 500
pixels per inch In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the ...
(ppi). WSQ was developed by the FBI, the Los Alamos National Lab, and the
National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...
(NIST). For fingerprints recorded at 1000 ppi spatial resolution, law enforcement (including the FBI) uses
JPEG 2000 JPEG 2000 (JP2) is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi (later the JPEG president), with the intention of superseding th ...
instead of WSQ.


Validity

Fingerprints collected at a crime scene, or on items of evidence from a crime, have been used in
forensic science Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal ...
to identify suspects, victims and other persons who touched a surface. Fingerprint identification emerged as an important system within police agencies in the late 19th century, when it replaced anthropometric measurements as a more reliable method for identifying persons having a prior record, often under a false name, in a criminal record repository. Fingerprinting has served all governments worldwide during the past 100 years or so to provide identification of criminals. Fingerprints are the fundamental tool in every police agency for the identification of people with a criminal history. The validity of forensic fingerprint evidence has been challenged by academics, judges and the media. In the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
fingerprint examiners have not developed uniform standards for the identification of an individual based on matching fingerprints. In some countries where fingerprints are also used in criminal investigations, fingerprint examiners are required to match a number of ''identification points'' before a match is accepted. In England 16 identification points are required and in France 12, to match two fingerprints and identify an individual. Point-counting methods have been challenged by some fingerprint examiners because they focus solely on the location of particular characteristics in fingerprints that are to be matched. Fingerprint examiners may also uphold the ''one dissimilarity doctrine'', which holds that if there is one dissimilarity between two fingerprints, the fingerprints are not from the same finger. Furthermore, academics have argued that the error rate in matching fingerprints has not been adequately studied. And it has been argued that fingerprint evidence has no secure
statistical Statistics (from German: '' Statistik'', "description of a state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industr ...
foundation. Research has been conducted into whether experts can objectively focus on feature information in fingerprints without being misled by extraneous information, such as context. Fingerprints can theoretically be forged and planted at crime scenes.


Professional certification

Fingerprinting was the basis upon which the first forensic professional organization was formed, the International Association for Identification (IAI), in 1915. The first professional certification program for forensic scientists was established in 1977, the IAI's Certified Latent Print Examiner program, which issued certificates to those meeting stringent criteria and had the power to revoke certification where an individual's performance warranted it. Other forensic disciplines have followed suit and established their own certification programs.


History


Antiquity and the medieval period

Fingerprints have been found on ancient
clay tablet In the Ancient Near East, clay tablets (Akkadian ) were used as a writing medium, especially for writing in cuneiform, throughout the Bronze Age and well into the Iron Age. Cuneiform characters were imprinted on a wet clay tablet with a sty ...
s, seals, and pottery. They have also been found on the walls of Egyptian tombs and on Minoan, Greek, and Chinese pottery. In
ancient China The earliest known written records of the history of China date from as early as 1250 BC, from the Shang dynasty (c. 1600–1046 BC), during the reign of king Wu Ding. Ancient historical texts such as the '' Book of Documents'' (early chapt ...
officials authenticated government documents with their fingerprints. In about 200 BC fingerprints were used to sign written
contracts A contract is a legally enforceable agreement between two or more parties that creates, defines, and governs mutual rights and obligations between them. A contract typically involves the transfer of goods, services, money, or a promise to tr ...
in
Babylon ''Bābili(m)'' * sux, 𒆍𒀭𒊏𒆠 * arc, 𐡁𐡁𐡋 ''Bāḇel'' * syc, ܒܒܠ ''Bāḇel'' * grc-gre, Βαβυλών ''Babylṓn'' * he, בָּבֶל ''Bāvel'' * peo, 𐎲𐎠𐎲𐎡𐎽𐎢 ''Bābiru'' * elx, 𒀸𒁀𒉿𒇷 ''Babi ...
. Fingerprints from 3D-scans of cuneiform tablets are extracted using the
GigaMesh Software Framework The GigaMesh Software Framework is a free and open-source software for display, editing and visualization of 3D-data typically acquired with structured light or structure from motion. It provides numerous functions for analysis of archaeologic ...
. With the advent of silk and paper in China, parties to a legal contract impressed their handprints on the document. Sometime before 851 CE, an Arab merchant in China, Abu Zayd Hasan, witnessed Chinese merchants using fingerprints to authenticate loans. Although ancient peoples probably did not realize that fingerprints could uniquely identify individuals, references from the age of the Babylonian king
Hammurabi Hammurabi (Akkadian: ; ) was the sixth Amorite king of the Old Babylonian Empire, reigning from to BC. He was preceded by his father, Sin-Muballit, who abdicated due to failing health. During his reign, he conquered Elam and the city-states ...
(reigned 1792–1750 BCE) indicate that law officials would take the fingerprints of people who had been arrested. During China's
Qin Dynasty The Qin dynasty ( ; zh, c=秦朝, p=Qín cháo, w=), or Ch'in dynasty in Wade–Giles romanization ( zh, c=, p=, w=Ch'in ch'ao), was the first dynasty of Imperial China. Named for its heartland in Qin state (modern Gansu and Shaanxi), ...
, records have shown that officials took hand prints and foot prints as well as fingerprints as evidence from a crime scene. In 650 the Chinese historian Kia Kung-Yen remarked that fingerprints could be used as a means of authentication. In his '' Jami al-Tawarikh'' (Universal History), the Iranian physician Rashid-al-Din Hamadani (1247–1318) refers to the Chinese practice of identifying people via their fingerprints, commenting: "Experience shows that no two individuals have fingers exactly alike."


Europe in the 17th and 18th centuries

From the late 16th century onwards, European academics attempted to include fingerprints in scientific studies. But plausible conclusions could be established only from the mid-17th century onwards. In 1686 the professor of anatomy at the
University of Bologna The University of Bologna ( it, Alma Mater Studiorum – Università di Bologna, UNIBO) is a public research university in Bologna, Italy. Founded in 1088 by an organised guild of students (''studiorum''), it is the oldest university in contin ...
Marcello Malpighi identified ridges, spirals and loops in fingerprints left on surfaces. In 1788 a German anatomist
Johann Christoph Andreas Mayer Johann Christophe Andreas Mayer (December 8, 1747 – November 1801) was a German anatomist. Mayer worked in Berlin and later Frankfurt. In 1788, he was the first European to recognize that fingerprint A fingerprint is an impression lef ...
was the first European to conclude that fingerprints were unique to each individual. In 1880
Henry Faulds Henry Faulds (1 June 1843 – 24 March 1930) was a Scottish doctor, missionary and scientist who is noted for the development of fingerprinting. Early life Faulds was born in Beith, North Ayrshire, into a family of modest means. Aged 13, he wa ...
suggested, based on his studies, that fingerprints are unique to a human.


19th century

In 1823 Jan Evangelista Purkyně identified nine fingerprint patterns. The nine patterns include the tented arch, the loop, and the whorl, which in modern-day forensics are considered ridge details. In 1840, following the murder of Lord William Russell, a provincial doctor, Robert Blake Overton, wrote to
Scotland Yard Scotland Yard (officially New Scotland Yard) is the headquarters of the Metropolitan Police, the territorial police force responsible for policing Greater London's 32 boroughs, but not the City of London, the square mile that forms London's ...
suggesting checking for fingerprints. In 1853 the German anatomist Georg von Meissner (1829–1905) studied friction ridges, and in 1858 Sir William James Herschel initiated fingerprinting in India. In 1877 he first instituted the use of fingerprints on contracts and deeds to prevent the repudiation of signatures in Hooghly near
Kolkata Kolkata (, or , ; also known as Calcutta , the official name until 2001) is the capital of the Indian state of West Bengal, on the eastern bank of the Hooghly River west of the border with Bangladesh. It is the primary business, comme ...
and he registered government pensioners' fingerprints to prevent the collection of money by relatives after a pensioner's death. In 1880
Henry Faulds Henry Faulds (1 June 1843 – 24 March 1930) was a Scottish doctor, missionary and scientist who is noted for the development of fingerprinting. Early life Faulds was born in Beith, North Ayrshire, into a family of modest means. Aged 13, he wa ...
, a Scottish surgeon in a Tokyo hospital, published his first paper on the usefulness of fingerprints for identification and proposed a method to record them with printing ink. Returning to Great Britain in 1886, he offered the concept to the
Metropolitan Police The Metropolitan Police Service (MPS), formerly and still commonly known as the Metropolitan Police (and informally as the Met Police, the Met, Scotland Yard, or the Yard), is the territorial police force responsible for law enforcement and ...
in London but it was dismissed at that time. Up until the early 1890s police forces in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
and on the European continent could not reliably identify criminals to track their
criminal record A criminal record, police record, or colloquially RAP sheet (Record of Arrests and Prosecutions) is a record of a person's criminal history. The information included in a criminal record and the existence of a criminal record varies between coun ...
.
Francis Galton Sir Francis Galton, FRS FRAI (; 16 February 1822 – 17 January 1911), was an English Victorian era polymath: a statistician, sociologist, psychologist, Anthropology, anthropologist, tropical Exploration, explorer, geographer, Inventio ...
published a detailed statistical model of fingerprint analysis and identification in his 1892 book ''Finger Prints''. He had calculated that the chance of a "false positive" (two different individuals having the same fingerprints) was about 1 in 64 billion. In 1892 Juan Vucetich, an Argentine chief police officer, created the first method of recording the fingerprints of individuals on file. In that same year,
Francisca Rojas Francisca Rojas is believed to be the first criminal found guilty through fingerprint evidence in the world. On 29 June 1892, 27-year-old Rojas murdered her two children in Necochea, Buenos Aires Province, in Argentina. Her six-year-old son, Ponc ...
was found in a house with neck injuries, whilst her two sons were found dead with their throats cut. Rojas accused a neighbour, but despite brutal interrogation, this neighbour would not confess to the crimes. Inspector Álvarez, a colleague of Vucetich, went to the scene and found a bloody thumb mark on a door. When it was compared with Rojas' prints, it was found to be identical with her right thumb. She then confessed to the murder of her sons., cited in This was the first known murder case to be solved using fingerprint analysis. In
Kolkata Kolkata (, or , ; also known as Calcutta , the official name until 2001) is the capital of the Indian state of West Bengal, on the eastern bank of the Hooghly River west of the border with Bangladesh. It is the primary business, comme ...
a fingerprint Bureau was established in 1897, after the Council of the Governor General approved a committee report that fingerprints should be used for the classification of criminal records. The bureau employees Azizul Haque and Hem Chandra Bose have been credited with the primary development of a fingerprint classification system eventually named after their supervisor, Sir Edward Richard Henry.


20th century

The French scientist Paul-Jean Coulier developed a method to transfer latent fingerprints on surfaces to paper using
iodine Iodine is a chemical element with the Symbol (chemistry), symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , ...
fuming. It allowed the London
Scotland Yard Scotland Yard (officially New Scotland Yard) is the headquarters of the Metropolitan Police, the territorial police force responsible for policing Greater London's 32 boroughs, but not the City of London, the square mile that forms London's ...
to start fingerprinting individuals and identify criminals using fingerprints in 1901. Soon after, American police departments adopted the same method and fingerprint identification became a standard practice in the United States. The Scheffer case of 1902 is the first case of the identification, arrest, and conviction of a murderer based upon fingerprint evidence.
Alphonse Bertillon Alphonse Bertillon (; 22 April 1853 – 13 February 1914) was a French police officer and biometrics researcher who applied the anthropological technique of anthropometry to law enforcement creating an identification system based on physical me ...
identified the thief and murderer Scheffer, who had previously been arrested and his fingerprints filed some months before, from the fingerprints found on a fractured glass showcase, after a theft in a dentist's apartment where the dentist's employee was found dead. It was able to be proved in court that the fingerprints had been made after the showcase was broken. The identification of individuals through fingerprints for
law enforcement Law enforcement is the activity of some members of government who act in an organized manner to enforce the law by discovering, deterring, rehabilitating, or punishing people who violate the rules and norms governing that society. The term ...
has been considered essential in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
since the beginning of the 20th century.
Body identification Body identification is a subfield of forensic science that uses a variety of scientific and non-scientific methods to identify a body. Forensic purposes are served by rigorous scientific forensic identification techniques, but these are generall ...
using fingerprints has also been valuable in the aftermath of
natural disaster A natural disaster is "the negative impact following an actual occurrence of natural hazard in the event that it significantly harms a community". A natural disaster can cause loss of life or damage property, and typically leaves some econ ...
s and
anthropogenic hazard Anthropogenic hazards are hazards caused by human action or inaction. They are contrasted with natural hazards. Anthropogenic hazards may adversely affect humans, other organisms, biomes, and ecosystems. They can even cause an omnicide. The freq ...
s. In the United States, the FBI manages a fingerprint identification system and database called the Integrated Automated Fingerprint Identification System (IAFIS), which currently holds the fingerprints and criminal records of over 51 million criminal record subjects and over 1.5 million civil (non-criminal) fingerprint records. OBIM, formerly U.S. VISIT, holds the largest repository of biometric identifiers in the U.S. government at over 260 million individual identities. When it was deployed in 2004, this repository, known as the Automated Biometric Identification System (IDENT), stored biometric data in the form of two-finger records. Between 2005 and 2009, the
DHS The United States Department of Homeland Security (DHS) is the U.S. federal executive department responsible for public security, roughly comparable to the interior or home ministries of other countries. Its stated missions involve anti-ter ...
transitioned to a ten-print record standard in order to establish interoperability with IAFIS. In 1910, Edmond Locard established the first forensic lab in France. Criminals may wear gloves to avoid leaving fingerprints. However, the gloves themselves can leave prints that are as unique as human fingerprints. After collecting glove prints, law enforcement can match them to gloves that they have collected as evidence or to prints collected at other crime scenes. In many
jurisdictions Jurisdiction (from Latin 'law' + 'declaration') is the legal term for the legal authority granted to a legal entity to enact justice. In federations like the United States, areas of jurisdiction apply to local, state, and federal levels. Ju ...
the act of wearing gloves itself while committing a crime can be prosecuted as an inchoate offense.James W.H. McCord and Sandra L. McCord, ''Criminal Law and Procedure for the paralegal: a systems approach'', ''supra'', p. 127.


Use of fingerprints in schools

The
non-governmental organization A non-governmental organization (NGO) or non-governmental organisation (see spelling differences) is an organization that generally is formed independent from government. They are typically nonprofit entities, and many of them are active in ...
(NGO)
Privacy International Privacy International (PI) is a UK-based registered charity that defends and promotes the right to privacy across the world. First formed in 1990, registered as a non-profit company in 2002 and as a charity in 2012, PI is based in London. Its ...
in 2002 made the cautionary announcement that tens of thousands of UK school children were being fingerprinted by schools, often without the knowledge or consent of their parents.Fingerprinting of UK school kids causes outcry
, ''
The Register ''The Register'' is a British technology news website co-founded in 1994 by Mike Magee, John Lettice and Ross Alderson. The online newspaper's masthead sublogo is "''Biting the hand that feeds IT''." Their primary focus is information tec ...
'', July 22, 2002
That same year, the supplier
Micro Librarian Systems Micro may refer to: Measurement * micro- (μ), a metric prefix denoting a factor of 10−6 Places * Micro, North Carolina, town in U.S. People * DJ Micro, (born Michael Marsicano) an American trance DJ and producer * Chii Tomiya (都宮 ち ...
, which uses a technology similar to that used in US prisons and the German military, estimated that 350 schools throughout Britain were using such systems to replace library cards. By 2007, it was estimated that 3,500 schools were using such systems.Child fingerprint plan considered
, '' BBC'', March 4, 2007
Under the United Kingdom Data Protection Act, schools in the UK do not have to ask parental consent to allow such practices to take place. Parents opposed to fingerprinting may bring only individual complaints against schools. In response to a complaint which they are continuing to pursue, in 2010 the
European Commission The European Commission (EC) is the executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body ...
expressed 'significant concerns' over the proportionality and necessity of the practice and the lack of judicial redress, indicating that the practice may break the
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are located primarily in Europe, Europe. The union has a total area of ...
data protection directive. In March 2007, the UK government was considering fingerprinting all children aged 11 to 15 and adding the prints to a government database as part of a new
passport A passport is an official travel document issued by a government that contains a person's identity. A person with a passport can travel to and from foreign countries more easily and access consular assistance. A passport certifies the personal ...
and ID card scheme and disallowing opposition for privacy concerns. All fingerprints taken would be cross-checked against prints from 900,000 unsolved crimes. Shadow Home secretary David Davis called the plan "sinister". The Liberal Democrat home affairs spokesman
Nick Clegg Sir Nicholas William Peter Clegg (born 7 January 1967) is a British media executive and former Deputy Prime Minister of the United Kingdom who has been president for global affairs at Meta Platforms since 2022, having previously been vicep ...
criticised "the determination to build a surveillance state behind the backs of the British people". The UK's junior education minister
Lord Adonis Andrew Adonis, Baron Adonis, (born Andreas Adonis; 22 February 1963) is a British Labour Party politician and journalist who served in HM Government for five years in the Blair ministry and the Brown ministry. He served as Secretary of State ...
defended the use of fingerprints by schools, to track school attendance as well as access to school meals and
libraries A library is a collection of Document, materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or electronic media, digital access (soft copies) materials, and may be a ...
, and reassured the
House of Lords The House of Lords, also known as the House of Peers, is the upper house of the Parliament of the United Kingdom. Membership is by appointment, heredity or official function. Like the House of Commons, it meets in the Palace of Westminst ...
that the children's fingerprints had been taken with the consent of the parents and would be destroyed once children left the school. An
Early Day Motion In the Westminster parliamentary system, an early day motion (EDM) is a motion, expressed as a single sentence, tabled by members of Parliament that formally calls for debate "on an early day". In practice, they are rarely debated in the House ...
which called on the UK Government to conduct a full and open consultation with stakeholders about the use of biometrics in schools, secured the support of 85
Members of Parliament A member of parliament (MP) is the representative in parliament of the people who live in their electoral district. In many countries with bicameral parliaments, this term refers only to members of the lower house since upper house members of ...
(Early Day Motion 686). Following the establishment in the United Kingdom of a Conservative and Liberal Democratic coalition government in May 2010, the
UK ID card scheme The Identity Cards Act 2006 (c. 15) was an Act of the Parliament of the United Kingdom that was repealed in 2011. It created national identity cards, a personal identification document and European Economic Area travel document, linked to a ...
was scrapped. Serious concerns about the security implications of using conventional biometric templates in schools have been raised by a number of leading IT security experts, one of whom has voiced the opinion that "it is absolutely premature to begin using 'conventional biometrics' in schools". The vendors of biometric systems claim that their products bring benefits to schools such as improved reading skills, decreased wait times in lunch lines and increased revenues. They do not cite independent research to support this view. One education specialist wrote in 2007: "I have not been able to find a single piece of published research which suggests that the use of biometrics in schools promotes healthy eating or improves reading skills amongst children... There is absolutely no evidence for such claims". The
Ottawa Ottawa (, ; Canadian French: ) is the capital city of Canada. It is located at the confluence of the Ottawa River and the Rideau River in the southern portion of the province of Ontario. Ottawa borders Gatineau, Quebec, and forms the c ...
Police in Canada have advised parents who fear their children may be kidnapped to fingerprint their children.


Absence or mutilation of fingerprints

A very rare medical condition,
adermatoglyphia Adermatoglyphia is an extremely rare genetic disorder that prevents the development of fingerprints. Five extended families worldwide are known to be affected by this condition. The disorder was informally nicknamed "immigration delay disease" by ...
, is characterized by the absence of fingerprints. Affected persons have completely smooth fingertips, palms, toes and soles, but no other medical signs or symptoms. A 2011 study indicated that adermatoglyphia is caused by the improper expression of the
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
SMARCAD1 SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily A containing DEAD/H box 1 is a protein that in humans is encoded by the ''SMARCAD1'' gene. Proper expression of SMARCAD1 may be important to fingerprint developmen ...
. The condition has been called ''immigration delay disease'' by the researchers describing it, because the congenital lack of fingerprints causes delays when affected persons attempt to prove their identity while traveling. Only five families with this condition had been described as of 2011. People with Naegeli–Franceschetti–Jadassohn syndrome and dermatopathia pigmentosa reticularis, which are both forms of ectodermal dysplasia, also have no fingerprints. Both of these rare genetic syndromes produce other signs and symptoms as well, such as thin, brittle hair. The anti-cancer medication capecitabine may cause the loss of fingerprints. Swelling of the fingers, such as that caused by bee stings, will in some cases cause the temporary disappearance of fingerprints, though they will return when the swelling recedes. Since the elasticity of skin decreases with age, many
senior citizen Old age refers to ages nearing or surpassing the life expectancy of human beings, and is thus the end of the human life cycle. Terms and euphemisms for people at this age include old people, the elderly (worldwide usage), OAPs (British usage ...
s have fingerprints that are difficult to capture. The ridges get thicker; the height between the top of the ridge and the bottom of the furrow gets narrow, so there is less prominence. Fingerprints can be erased permanently and this can potentially be used by criminals to reduce their chance of conviction. Erasure can be achieved in a variety of ways including simply burning the fingertips, using acids and advanced techniques such as
plastic surgery Plastic surgery is a surgical specialty involving the restoration, reconstruction or alteration of the human body. It can be divided into two main categories: reconstructive surgery and cosmetic surgery. Reconstructive surgery includes cranio ...
.
John Dillinger John Herbert Dillinger (June 22, 1903 – July 22, 1934) was an American gangster during the Great Depression. He led the Dillinger Gang, which was accused of robbing 24 banks and four police stations. Dillinger was imprisoned several times an ...
burned his fingers with acid, but prints taken during a previous arrest and upon death still exhibited almost complete relation to one another.


Fingerprint verification

Fingerprints can be captured as graphical ridge and valley patterns. Because of their uniqueness and permanence, fingerprints emerged as the most widely used
biometric Biometrics are body measurements and calculations related to human characteristics. Biometric authentication (or realistic authentication) is used in computer science as a form of identification and access control. It is also used to identify in ...
identifier in the 2000s.
Automated fingerprint verification Automated fingerprint identification is the process of using a computer to match fingerprints against a database of known and unknown prints in the fingerprint identification system. Automated fingerprint identification systems (AFIS) are primari ...
systems were developed to meet the needs of
law enforcement Law enforcement is the activity of some members of government who act in an organized manner to enforce the law by discovering, deterring, rehabilitating, or punishing people who violate the rules and norms governing that society. The term ...
and their use became more widespread in civilian applications. Despite being deployed more widely, reliable automated fingerprint verification remained a challenge and was extensively researched in the context of
pattern recognition Pattern recognition is the automated recognition of patterns and regularities in data. It has applications in statistical data analysis, signal processing, image analysis, information retrieval, bioinformatics, data compression, computer graphics ...
and
image processing An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensio ...
. The uniqueness of a fingerprint can be established by the overall pattern of ridges and valleys, or the logical ridge discontinuities known as minutiae. In the 2000s minutiae features were considered the most discriminating and reliable feature of a fingerprint. Therefore, the recognition of minutiae features became the most common basis for automated fingerprint verification. The most widely used minutiae features used for automated fingerprint verification were the ridge ending and the ridge bifurcation.


Patterns

The three basic patterns of fingerprint ridges are the arch, loop, and whorl: * Arch: The ridges enter from one side of the finger, rise in the center forming an arc, and then exit the other side of the finger. * Loop: The ridges enter from one side of a finger, form a curve, and then exit on that same side. * Whorl: Ridges form circularly around a central point on the finger. Scientists have found that family members often share the same general fingerprint patterns, leading to the belief that these patterns are inherited.


Minutiae features

Features of fingerprint ridges, called '' minutiae'', include: * Ridge ending: The abrupt end of a ridge * Bifurcation: A single ridge dividing in two * Short or independent ridge: A ridge that commences, travels a short distance and then ends * Island or dot: A single small ridge inside a short ridge or ridge ending that is not connected to all other ridges * Lake or ridge enclosure: A single ridge that bifurcates and reunites shortly afterward to continue as a single ridge * Spur: A bifurcation with a short ridge branching off a longer ridge * Bridge or crossover: A short ridge that runs between two parallel ridges * Delta: A Y-shaped ridge meeting * Core: A circle in the ridge pattern


Fingerprint sensors

A fingerprint
sensor A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
is an
electronic device The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
used to capture a
digital image A digital image is an image composed of picture elements, also known as ''pixels'', each with '' finite'', '' discrete quantities'' of numeric representation for its intensity or gray level that is an output from its two-dimensional functions ...
of the fingerprint pattern. The captured image is called a live scan. This live scan is digitally processed to create a biometric template (a collection of extracted features) which is stored and used for matching. Many technologies have been used including
optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
, capacitive, RF, thermal, piezoresistive, ultrasonic,
piezoelectric Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word '' ...
, and
MEMS Microelectromechanical systems (MEMS), also written as micro-electro-mechanical systems (or microelectronic and microelectromechanical systems) and the related micromechatronics and microsystems constitute the technology of microscopic devices, ...
. * Optical scanners take a visual image of the fingerprint using a digital camera. * Capacitive or CMOS scanners use capacitors and thus electrical current to form an image of the fingerprint. * Ultrasound fingerprint scanners use high frequency sound waves to penetrate the epidermal (outer) layer of the skin. * Thermal scanners sense the temperature differences on the contact surface, in between fingerprint ridges and valleys.


Consumer electronics login authentication

Since 2000 electronic fingerprint readers have been introduced as
consumer electronics Consumer electronics or home electronics are electronic ( analog or digital) equipment intended for everyday use, typically in private homes. Consumer electronics include devices used for entertainment, communications and recreation. Usuall ...
security applications. Fingerprint sensors could be used for
login In computer security, logging in (or logging on, signing in, or signing on) is the process by which an individual gains access to a computer system by identifying and authenticating themselves. The user credentials are typically some fo ...
authentication Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an assertion, such as the identity of a computer system user. In contrast with identification, the act of indicatin ...
and the identification of computer users. However, some less sophisticated sensors have been discovered to be vulnerable to quite simple methods of deception, such as fake fingerprints cast in
gel A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still di ...
s. In 2006, fingerprint sensors gained popularity in the
laptop A laptop, laptop computer, or notebook computer is a small, portable personal computer (PC) with a screen and alphanumeric keyboard. Laptops typically have a clam shell form factor with the screen mounted on the inside of the upper li ...
market. Built-in sensors in laptops, such as ThinkPads, VAIO, HP Pavilion and
EliteBook HP EliteBook is a line of business-oriented high-end notebooks and mobile workstations made by Hewlett-Packard (HP Inc.). The EliteBook series, which fits above the lower-end ProBook series, was introduced in August 2008 as a replacement of the ...
laptops, and others also double as
motion detector A motion detector is an electrical device that utilizes a sensor to detect nearby motion. Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area. They form a vital c ...
s for document scrolling, like the
scroll wheel A scroll wheel is a wheel used for scrolling. The term usually refers to such wheels found on computer mice (where they can also be called a mouse wheel). It is often made of hard plastic with a rubbery surface, centred around an internal rota ...
. Two of the first smartphone manufacturers to integrate fingerprint recognition into their phones were Motorola with the Atrix 4G in 2011 and Apple with the
iPhone 5S The iPhone 5S (stylized and marketed as iPhone 5s) is a smartphone that was designed and marketed by Apple Inc. It is the seventh generation of the iPhone, succeeding the iPhone 5, and unveiled in September 2013, alongside the iPhone 5C. ...
on September 10, 2013. One month after, HTC launched the One Max, which also included fingerprint recognition. In April 2014, Samsung released the
Galaxy S5 The Samsung Galaxy S5 is an Android-based smartphone unveiled, produced, released and marketed by Samsung Electronics as part of the Samsung Galaxy S series. Unveiled on 24 February 2014 at Mobile World Congress in Barcelona, Spain, it was rele ...
, which integrated a fingerprint sensor on the home button. Following the release of the
iPhone 5S The iPhone 5S (stylized and marketed as iPhone 5s) is a smartphone that was designed and marketed by Apple Inc. It is the seventh generation of the iPhone, succeeding the iPhone 5, and unveiled in September 2013, alongside the iPhone 5C. ...
model, a group of German hackers announced on September 21, 2013, that they had bypassed Apple's new Touch ID fingerprint sensor by photographing a fingerprint from a glass surface and using that captured image as verification. The spokesman for the group stated: "We hope that this finally puts to rest the illusions people have about fingerprint biometrics. It is plain stupid to use something that you can't change and that you leave everywhere every day as a security token." In September 2015, Apple included a new version of the fingerprint scanner in the iPhone home button with the iPhone 6S. The use of the Touch ID fingerprint scanner was optional and could be configured to unlock the screen or pay for
mobile app A mobile application or app is a computer program or software application designed to run on a mobile device such as a phone, tablet, or watch. Mobile applications often stand in contrast to desktop applications which are designed to run on d ...
s purchases. Since December 2015, cheaper smartphones with fingerprint recognition have been released, such as the $100 UMI Fair.
Samsung The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...
introduced fingerprint sensors to its mid-range A series smartphones in 2014. By 2017
Hewlett Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...
, Asus,
Huawei Huawei Technologies Co., Ltd. ( ; ) is a Chinese multinational technology corporation headquartered in Shenzhen, Guangdong, China. It designs, develops, produces and sells telecommunications equipment, consumer electronics and various sma ...
,
Lenovo Lenovo Group Limited, often shortened to Lenovo ( , ), is a Chinese multinational technology company specializing in designing, manufacturing, and marketing consumer electronics, personal computers, software, business solutions, and related se ...
and
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
were using fingerprint readers in their laptops. Synaptics says the SecurePad sensor is now available for OEMs to start building into their laptops. In 2018, Synaptics revealed that their in-display fingerprint sensors would be featured on the new Vivo X21 UD smartphone. This was the first mass-produced fingerprint sensor to be integrated into the entire touchscreen display, rather than as a separate sensor.


Video

Videos have become a pronounced way of identifying information. There are features in videos that look at how intense certain parts of a frame are compared to others which help with identification.


Algorithms

Matching
algorithms In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...
are used to compare previously stored templates of fingerprints against candidate fingerprints for
authentication Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an assertion, such as the identity of a computer system user. In contrast with identification, the act of indicatin ...
purposes. In order to do this either the original image must be directly compared with the candidate image or certain features must be compared.


Pre-processing

Pre-processing enhances the quality of an image by filtering and removing extraneous noise. The minutiae-based algorithm is only effective with 8-bit gray scale fingerprint images. One reason for this is that an 8-bit gray fingerprint image is a fundamental base when converting the image to a 1-bit image with value 1 for ridges and value 0 for furrows. This process allows for enhanced edge detection so the fingerprint is revealed in high contrast, with the ridges highlighted in black and the furrows in white. To further optimize the input image's quality, two more steps are required: minutiae extraction and false minutiae removal. The minutiae extraction is carried out by applying a ridge-thinning algorithm that removes redundant pixels of ridges. As a result, the thinned ridges of the fingerprint image are marked with a unique ID to facilitate the conduction of further operations. After the minutiae extraction, the false minutiae removal is carried out. The lack of the amount of ink and the cross link among the ridges could cause false minutiae that led to inaccuracy in fingerprint recognition process.


Pattern-based (or image-based) algorithms

Pattern based algorithms compare the basic fingerprint patterns (arch, whorl, and loop) between a previously stored template and a candidate fingerprint. This requires that the images can be aligned in the same orientation. To do this, the algorithm finds a central point in the fingerprint image and centers on that. In a pattern-based algorithm, the template contains the type, size, and orientation of patterns within the aligned fingerprint image. The candidate fingerprint image is graphically compared with the template to determine the degree to which they match.