
A detective is an investigator, usually a member of a
law enforcement agency
A law enforcement agency (LEA) is any government agency responsible for law enforcement within a specific jurisdiction through the employment and deployment of law enforcement officers and their resources. The most common type of law enforcement ...
. They often collect information to solve
crime
In ordinary language, a crime is an unlawful act punishable by a State (polity), state or other authority. The term ''crime'' does not, in modern criminal law, have any simple and universally accepted definition,Farmer, Lindsay: "Crime, definiti ...
s by talking to witnesses and informants, collecting physical evidence, or searching records in databases. This leads them to arrest criminals and enable them to be convicted in court.
A detective may work for the
police
The police are Law enforcement organization, a constituted body of Law enforcement officer, people empowered by a State (polity), state with the aim of Law enforcement, enforcing the law and protecting the Public order policing, public order ...
or
privately.
Overview

Informally, and primarily in
fiction
Fiction is any creative work, chiefly any narrative work, portraying character (arts), individuals, events, or setting (narrative), places that are imagination, imaginary or in ways that are imaginary. Fictional portrayals are thus inconsistent ...
, a detective is a licensed or unlicensed person who solves
crime
In ordinary language, a crime is an unlawful act punishable by a State (polity), state or other authority. The term ''crime'' does not, in modern criminal law, have any simple and universally accepted definition,Farmer, Lindsay: "Crime, definiti ...
s, including historical crimes, by examining and evaluating clues and personal records in order to uncover the identity and/or whereabouts of criminals.
In some
police departments, a detective position is obtained by passing a written test after a person completes the requirements for being a
police officer
A police officer (also called policeman or policewoman, cop, officer or constable) is a Warrant (law), warranted law employee of a police, police force. In most countries, ''police officer'' is a generic term not specifying a particular rank. ...
. In many other police systems, detectives are college graduates who join directly from
civilian
A civilian is a person who is not a member of an armed force. It is war crime, illegal under the law of armed conflict to target civilians with military attacks, along with numerous other considerations for civilians during times of war. If a civi ...
life without first serving as uniformed officers. Some argue that detectives do a completely different job and therefore require completely different training, qualifications, qualities, and abilities than uniformed officers. The other side says that a detective who has worked as a uniformed officer will excel as a private detective due to their knowledge about standard police procedures, their contact network and their own experience with typical problems.
Some are not public officials, and may be known as a
private investigator
A private investigator (often abbreviated to PI; also known as a private detective, an inquiry agent or informally a wikt:private eye, private eye) is a person who can be hired by individuals or groups to undertake investigatory law services. ...
, colloquially referred to, especially in fiction, as a "PI" or "private eye", "private ducky" or "shamus".
Organization
The detective branch in most large police agencies is organized into several squads and departments, each of which specializes in
investigation into a particular type of crime or a particular type of undercover operation, which may include:
homicide
Homicide is an act in which a person causes the death of another person. A homicide requires only a Volition (psychology), volitional act, or an omission, that causes the death of another, and thus a homicide may result from Accident, accidenta ...
,
robbery
Robbery is the crime of taking or attempting to take anything of value by force, threat of force, or use of fear. According to common law, robbery is defined as taking the property of another, with the intent to permanently deprive the person o ...
,
burglary
Burglary, also called breaking and entering (B&E) or housebreaking, is a property crime involving the illegal entry into a building or other area without permission, typically with the intention of committing a further criminal offence. Usually ...
,
auto theft,
organized crime
Organized crime is a category of transnational organized crime, transnational, national, or local group of centralized enterprises run to engage in illegal activity, most commonly for profit. While organized crime is generally thought of as a f ...
s,
missing person
A missing person is a person who has disappeared and whose status as Life, alive or Death, dead cannot be confirmed as their location and condition are unknown. A person may go missing through a voluntary disappearance, or else due to an accide ...
s,
juvenile crime,
fraud
In law, fraud is intent (law), intentional deception to deprive a victim of a legal right or to gain from a victim unlawfully or unfairly. Fraud can violate Civil law (common law), civil law (e.g., a fraud victim may sue the fraud perpetrato ...
,
narcotic
The term narcotic (, from ancient Greek ναρκῶ ''narkō'', "I make numb") originally referred medically to any psychoactive compound with numbing or paralyzing properties. In the United States, it has since become associated with opiates ...
s,
vice
A vice is a practice, behaviour, Habit (psychology), habit or item generally considered morally wrong in the associated society. In more minor usage, vice can refer to a fault, a negative character trait, a defect, an infirmity, or a bad or unhe ...
,
criminal intelligence,
aggravated assault
In the terminology of law, an assault is the act of causing physical harm or unwanted physical contact to another person, or, in some legal definitions, the threat or attempt to do so. It is both a crime and a tort and, therefore, may result ...
/
battery,
sexual assault
Sexual assault is an act of sexual abuse in which one intentionally Physical intimacy, sexually touches another person without that person's consent, or Coercion, coerces or physically forces a person to engage in a sexual act against their w ...
,
computer crime
Cybercrime encompasses a wide range of criminal activities that are carried out using digital devices and/or networks. It has been variously defined as "a crime committed on a computer network, especially the Internet"; Cybercriminals may exp ...
,
domestic violence
Domestic violence is violence that occurs in a domestic setting, such as in a marriage
Marriage, also called matrimony or wedlock, is a culturally and often legally recognised union between people called spouses. It establishes r ...
,
surveillance
Surveillance is the monitoring of behavior, many activities, or information for the purpose of information gathering, influencing, managing, or directing. This can include observation from a distance by means of electronic equipment, such as ...
, and
arson
Arson is the act of willfully and deliberately setting fire to or charring property. Although the act of arson typically involves buildings, the term can also refer to the intentional burning of other things, such as motor vehicles, watercr ...
, among others.
In police departments of the United States, a regular detective typically holds the rank of "Detective". The rank structure of the officers who supervise them (who may or may not be detectives themselves) varies considerably by department. In some Commonwealth police forces, detectives have equivalent ranks to uniformed officers but with the word "Detective" prepended to it; e.g. "Detective Constable" (DC) or "
Detective Sergeant
Sergeant (Sgt) is a rank in use by the armed forces of many countries. It is also a police rank in some police services. The alternative spelling, ''serjeant'', is used in The Rifles and in other units that draw their heritage from the Brit ...
" (DS).
Private detectives
In some countries, courts and judicial processes have yet to recognize the practice of private detectives. In Portugal, presented proof loses significance when private detectives collect it. Even under these circumstances, the practice is in demand and governed by a code of conduct.
Citizen detectives
A citizen detective, also known as an amateur detective, is an individual who devotes his or her time and expertise to aid in the
solving of crime, without compensation or expectation of reward. Citizen detectives are
private citizen
A private citizen is a citizen who does not have an official or professional
A professional is a member of a profession or any person who work (human activity), works in a specified professional activity. The term also describes the standards ...
s that have no real professional relationship with law enforcement and lack any
rational-legal authority
Rational-legal authority (also known as rational authority, legal authority, rational domination, legal domination, or bureaucratic authority) is a form of leadership in which the authority of an organization or a ruling regime is largely tied to ...
whatsoever. The reasons why a private citizen might try to solve a crime vary from trying to ensure justice for a friend or relative, a strong dislike for crime and support for
law and order, or just recreational enjoyment.
As with other kinds of detectives, citizen detectives try to solve crimes in multiple ways such as
searching a crime scene,
interviewing
An interview is a structured conversation where one participant asks questions, and the other provides answers.Merriam Webster DictionaryInterview Dictionary definition, Retrieved February 16, 2016 In common parlance, the word "interview" re ...
and/or
interrogating
Interrogation (also called questioning) is interviewing as commonly employed by law enforcement officers, military personnel, intelligence agencies, organized crime syndicates, and terrorist organizations with the goal of eliciting useful info ...
suspect
In law enforcement jargon, a suspect is a known person accused or suspected of committing a crime. Police and reporters in the United States often use the word suspect as a jargon when referring to the perpetrator of the offense (perp in dated U. ...
s and witnesses, doing
surveillance
Surveillance is the monitoring of behavior, many activities, or information for the purpose of information gathering, influencing, managing, or directing. This can include observation from a distance by means of electronic equipment, such as ...
on
persons of interest, collecting
evidence
Evidence for a proposition is what supports the proposition. It is usually understood as an indication that the proposition is truth, true. The exact definition and role of evidence vary across different fields. In epistemology, evidence is what J ...
, acting as
sources
Source may refer to:
Research
* Historical document
* Historical source
* Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence
* Source (journalism), a person, publication, publishing institute ...
for
local news
In journalism, local news refers to coverage of events, by the news, in a local context that would not be of interest to another locality, or otherwise be of national or international scope. Local news, in contrast to national or international new ...
, giving anonymous tips to the police and at times even making
citizen's arrest
A citizen's arrest is an arrest made by a private citizen – a person who is not acting as a sworn Police officer, law-enforcement official. In common law jurisdictions, the practice dates back to medieval England and the English common law, in wh ...
s while a crime is being committed. Citizen detectives can also help law enforcement by becoming
witness
In law, a witness is someone who, either voluntarily or under compulsion, provides testimonial evidence, either oral or written, of what they know or claim to know.
A witness might be compelled to provide testimony in court, before a grand jur ...
es for
prosecutor
A prosecutor is a legal representative of the prosecution in states with either the adversarial system, which is adopted in common law, or inquisitorial system, which is adopted in Civil law (legal system), civil law. The prosecution is the ...
s, participating in local
neighborhood watch
A neighborhood watch or neighbourhood watch (see American and British English spelling differences#-our, -or, spelling differences), also called a crime watch or neighbourhood crime watch, is an organized group of civilians devoted to crime a ...
groups, acting as
citizen observers for law enforcement, or even aiding the police in searching for and arresting suspects as a
posse. However, there have been cases of citizen detectives unintentionally compromising investigations if they lack real crime solving skills or even committing acts against suspected criminals that could be deemed
vigilantism
Vigilantism () is the act of preventing, investigating, and punishing perceived offenses and crimes without legal authority.
A vigilante is a person who practices or partakes in vigilantism, or undertakes public safety and retributive justice ...
in nature.
History

Before the 19th century, there were few municipal police departments, though the first had been created in Paris as early as 1667. As police work went from being done by appointed people with help from volunteers to being done by professionals, the idea of dedicated detectives did not come up right away. The first
private detective agency was founded in Paris in 1833 by
Eugène François Vidocq
Eugene is a common male given name that comes from the Greek εὐγενής (''eugenēs''), "noble", literally "well-born", from εὖ (''eu''), "well" and γένος (''genos''), "race, stock, kin".Bow Street Runners
The Bow Street Runners were the law enforcement officers of the Bow Street Magistrates' Court in the City of Westminster. They have been called London's first professional police force. The force originally numbered six men and was founded in 1 ...
and later by the
Metropolitan Police Service in Greater London. The first police detective unit in the United States was formed in 1846 in Boston.
Techniques
Street work

Detectives have a wide variety of techniques available in conducting investigations. However, the majority of cases are solved by the interrogation of suspects and the interviewing of witnesses, which takes time. Detectives may also use their network of informants, which they have built up over the years. Informants often have connections with people a detective would not be able to approach formally. Evidence collection and preservation can also help in identifying a potential suspect(s).
Criminal investigation
Investigation of criminal activity is conducted by the police. Criminal activity can relate to road use such as speeding, drunk driving, or to matters such as theft, drug distribution, assault, fraud, etc. When the police have concluded their investigation, a decision on whether to charge somebody with a criminal offence will (depending on legal jurisdiction) often be made by prosecuting counsel having considered the evidence produced by the police.
In criminal investigations, once a detective has suspects in mind, the next step is to produce evidence that will stand up in a court of law. One way is to obtain a confession from the suspect; usually, this is done by developing rapport and, at times, by seeking information in exchange for potential perks available through the attorney's office, such as entering for a lesser sentence in exchange for usable information. In some countries, detectives may lie, mislead and psychologically pressure a suspect into an admission or confession as long as they do this within procedural boundaries and without the threat of violence or promises outside their control. This is not permitted in
England and Wales
England and Wales () is one of the Law of the United Kingdom#Legal jurisdictions, three legal jurisdictions of the United Kingdom. It covers the constituent countries England and Wales and was formed by the Laws in Wales Acts 1535 and 1542. Th ...
, where interview of suspects and witnesses is governed by the
Police and Criminal Evidence Act 1984
The Police and Criminal Evidence Act 1984 (c. 60) (PACE) is an act of Parliament which instituted a legislative framework for the powers of police officers in England and Wales to combat crime, and provided codes of practice for the exercise of t ...
and its extensive Codes of Practice.
Forensic evidence
Physical
forensic evidence
Forensic identification is the application of forensic science, or "forensics", and technology to identify specific objects from the trace evidence they leave, often at a crime scene or the scene of an accident. Forensic means "for the courts".
Hu ...
in an investigation may provide leads to closing a case.
Forensic science
Forensic science combines principles of law and science to investigate criminal activity. Through crime scene investigations and laboratory analysis, forensic scientists are able to link suspects to evidence. An example is determining the time and ...
(often shortened to forensics) is the application of a broad spectrum of sciences to answer questions of interest to the legal system. This may be in relation to a crime or to a civil action. Many major police stations in a city, county, or state, maintain their own forensic laboratories while others contract out the services.
Records investigation
Detectives may use public and private records to provide background information on a subject. Police detectives can search through files of fingerprint records. Police maintain records of people who have committed
felonies
A felony is traditionally considered a crime of high seriousness, whereas a misdemeanor is regarded as less serious. The term "felony" originated from English common law (from the French medieval word "''félonie''") to describe an offense that ...
and some
misdemeanor
A misdemeanor (American English, spelled misdemeanour elsewhere) is any "lesser" criminal act in some common law legal systems. Misdemeanors are generally punished less severely than more serious felonies, but theoretically more so than admi ...
s. Detectives may search through records of criminal arrests and convictions, photographs or "''mug shots''" of persons arrested, hotel registration information, credit reports,
answering machine
An answering machine, answerphone, or message machine, also known as telephone messaging machine (or TAM) in the United Kingdom, UK and some Commonwealth countries, ansaphone or ansafone (from a trade name), or telephone answering device (TAD), ...
messages, phone conversations, surveillance camera footage, and technology used for communication.
Worldwide
United Kingdom
Before 2017, prospective
British
British may refer to:
Peoples, culture, and language
* British people, nationals or natives of the United Kingdom, British Overseas Territories and Crown Dependencies.
* British national identity, the characteristics of British people and culture ...
police detectives must have completed at least two years as a uniformed officer before applying to join the
Criminal Investigation Department
The Criminal Investigation Department (CID) is the branch of a police force to which most plainclothes criminal investigation, detectives belong in the United Kingdom and many Commonwealth of Nations, Commonwealth nations. A force's CID is disti ...
. Since 2017, applicants from outside the police force have been able to apply directly for positions as trainee detectives.
UK Police must also pass the National Investigators' Examination in order to progress to subsequent stages of the Initial Crime Investigators Development Program in order to qualify as a detective.
United States

Before becoming a police detective, one must attend a law enforcement academy, which provides the officer with a foundation of education with 16 to 24
college units. After graduation from the law enforcement academy, the officer undergoes job training with a field training officer for a period specified by the law enforcement agency and continues to work while on a probationary period, ranging from one to two years.
During the probationary period, the officer is assigned to look for evidence. During this time, the officer is supervised and mentored by a sergeant with years of experience. Some police officers go to a two-year or four-year college or university to get a degree in criminal justice or the management of criminal justice. You can get a concentration or a certificate in a specialized field of criminal investigation at some colleges.
Through years of on-the-job training or college education, officers may participate in a competitive examination, testing their knowledge, skills and abilities regarding criminal investigation, criminal procedure, interview and interrogation, search and seizure, collection and preservation of evidence, investigative report writing, criminal law, court procedure, and providing testimony in court. Competitive examinations are conducted by selected senior law enforcement officials. Following testing, a list of results is provided by the department. At the department's discretion, some or all of the officers on the list are promoted to the rank of detective. Some departments have classes of detectives which increase the detective's rank after successful experience.
Private investigators are licensed by the state in which they work (some states do not require licensing, but most do). In addition to the state examination, applicants testing for a private investigation license must also meet stringent requirements, which include college education, a range of two to four years of full-time investigation experience and the successful adjudication of a criminal and civil background check conducted by state investigators. Private investigators are licensed to conduct civil and criminal investigations in the state in which they are licensed, and are protected by statutes of that state. In states requiring licensing, statutes make it unlawful for any person to conduct a criminal investigation without a license, unless exempted by the statute (i.e., law enforcement officers or agents, attorneys,
paralegals
A paralegal, also known as a legal assistant or paralegal specialist, is a legal professional who performs tasks that require knowledge of legal concepts but not the full expertise of a lawyer with an admission to practice law. The market for p ...
,
claims adjuster
Insurance is a means of protection from financial loss in which, in exchange for a fee, a party agrees to compensate another party in the event of a certain loss, damage, or injury. It is a form of risk management, primarily used to protect ...
s).
Vietnam
In
Vietnam
Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...
, private detective work is not yet officially recognized by law but is developing due to the demands of
modern society
Modernity, a topic in the humanities and social sciences, is both a historical period (the modern era) and the ensemble of particular socio-cultural norms, attitudes and practices that arose in the wake of the Renaissancein the Age of Reaso ...
. Detective service companies primarily offer investigation and surveillance services for
individuals and
businesses
Business is the practice of making one's living or making money by producing or buying and selling products (such as goods and services). It is also "any activity or enterprise entered into for profit."
A business entity is not necessari ...
in matters such as
marriage
Marriage, also called matrimony or wedlock, is a culturally and often legally recognised union between people called spouses. It establishes rights and obligations between them, as well as between them and their children (if any), and b ...
,
business fraud,
information retrieval
Information retrieval (IR) in computing and information science is the task of identifying and retrieving information system resources that are relevant to an Information needs, information need. The information need can be specified in the form ...
, or tracking subjects. The detective profession in
Vietnam
Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...
still lacks a clear legal framework and can easily fall into legal grey areas.
However, many detective companies have made efforts to provide
professional services Professional services are occupations in the service sector requiring special training in liberal arts and pure sciences education or professional development education. Some professional services, such as architects, accountants, engineers, d ...
, adhering to ethical standards and legal regulations to build trust with clients.
See also
*
Hotel detective
*
Inspector
Inspector, also police inspector or inspector of police, is a police rank. The rank or position varies in seniority depending on the organization that uses it.
Australia
The rank of Inspector is present in all Australian police forces excep ...
*
Investigator (disambiguation)
*
Law enforcement agency
A law enforcement agency (LEA) is any government agency responsible for law enforcement within a specific jurisdiction through the employment and deployment of law enforcement officers and their resources. The most common type of law enforcement ...
*
Police rank
*
Private investigator
A private investigator (often abbreviated to PI; also known as a private detective, an inquiry agent or informally a wikt:private eye, private eye) is a person who can be hired by individuals or groups to undertake investigatory law services. ...
*
Police
The police are Law enforcement organization, a constituted body of Law enforcement officer, people empowered by a State (polity), state with the aim of Law enforcement, enforcing the law and protecting the Public order policing, public order ...
*
Police officer
A police officer (also called policeman or policewoman, cop, officer or constable) is a Warrant (law), warranted law employee of a police, police force. In most countries, ''police officer'' is a generic term not specifying a particular rank. ...
*
Undercover operation
A covert operation or undercover operation is a military or police operation involving a covert agent or troops acting under an assumed cover to conceal the identity of the party responsible.
US law
Under US law, the Central Intelligence Ag ...
*
Spy agent
*
Special agent
In the United States, a special agent is an official title used to refer to certain investigators or detectives of federal, military, tribal, or state agencies who primarily serve in criminal investigatory positions. Additionally, some special ...
*
Detective fiction
Detective fiction is a subgenre of crime fiction and mystery fiction in which an criminal investigation, investigator or a detective—whether professional, amateur or retired—investigates a crime, often murder. The detective genre began around ...
*
VALCRI
References
{{Authority control, show=scong time ago
Criminal investigation
Police ranks
Law enforcement