Opinion evidence refers to direct evidence outlining what the expert witness, believes, or infers in regard to facts, as distinguished from personal knowledge of the facts themselves. In

common law jurisdiction In law, common law (also known as judicial precedent, judge-made law, or case law) is the body of law created by judges and similar quasi-judicial tribunals by virtue of being stated in written opinions."The common law is not a brooding omnipresen ...

s the general rule is that a witness is supposed to testify as to what was observed and not to give an opinion on what was observed. However, there are two exceptions to this rule:

expert evidence An expert witness, particularly in common law countries such as the United Kingdom, Australia, and the United States, is a person whose opinion by virtue of education, training, certification, skills or experience, is accepted by the judge a ...

and non-expert opinion given by laymen which people in their daily lives reach without conscious

ratiocination Reason is the capacity of consciously applying logic by drawing conclusions from new or existing information, with the aim of seeking the truth. It is closely associated with such characteristically human activities as philosophy, science, langu ...

General rule

In general, witnesses should testify only as to the facts observed and should not give opinion. The main rationale for such a rule is that the admission of opinion evidence would not assist, or might even mislead, the court and in particular the jury. This is because opinion evidence is usually irrelevant. Moreover, admission of such evidence would usurp the functions of the jury, which alone should be the tribunal of fact and draw its own inferences.

Expert evidence

An expert witness is a

witness In law, a witness is someone who has knowledge about a matter, whether they have sensed it or are testifying on another witnesses' behalf. In law a witness is someone who, either voluntarily or under compulsion, provides testimonial evidence, e ...

, who by virtue of

education Education is a purposeful activity directed at achieving certain aims, such as transmitting knowledge or fostering skills and character traits. These aims may include the development of understanding, rationality, kindness, and honesty. Va ...

training Training is teaching, or developing in oneself or others, any skills and knowledge or Physical fitness, fitness that relate to specific practicality, useful Competence (human resources), competencies. Training has specific goals of improving on ...

skill A skill is the learned ability to act with determined results with good execution often within a given amount of time, energy, or both. Skills can often be divided into domain-general and domain-specific skills. For example, in the domain of wo ...

, or

experience Experience refers to conscious events in general, more specifically to perceptions, or to the practical knowledge and familiarity that is produced by these conscious processes. Understood as a conscious event in the widest sense, experience involv ...

, is believed to have

expert An expert is somebody who has a broad and deep understanding and competence in terms of knowledge, skill and experience through practice and education in a particular field. Informally, an expert is someone widely recognized as a reliable s ...

ise and specialised

knowledge Knowledge can be defined as awareness of facts or as practical skills, and may also refer to familiarity with objects or situations. Knowledge of facts, also called propositional knowledge, is often defined as true belief that is distinc ...

in a particular subject beyond that of the average person, sufficient that others may officially and legally rely upon the witness's specialized (

scientific Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

, technical or other) opinion about an

evidence Evidence for a proposition is what supports this proposition. It is usually understood as an indication that the supported proposition is true. What role evidence plays and how it is conceived varies from field to field. In epistemology, evidenc ...

fact A fact is a datum about one or more aspects of a circumstance, which, if accepted as true and proven true, allows a logical conclusion to be reached on a true–false evaluation. Standard reference works are often used to check facts. Scient ...

issue within the scope of his expertise, referred to as the expert opinion, as an assistance to the

fact-finder A trier of fact or finder of fact is a person or group who determines which facts are available in a legal proceeding (usually a trial) and how relevant they are to deciding its outcome. To determine a fact is to decide, from the evidence present ...

. Expert witnesses may also deliver expert evidence about facts from the domain of their expertise. The facts upon which an expert opinion is based must be proved by admissible evidence. The duty of experts is to furnish the judge with the necessary scientific criteria for testing the accuracy of their conclusions, so that the judge or jury can form their own independent judgment by the application of these criteria to the facts proved.

Non-expert opinion

Non-expert opinion refers to the opinion given in restricted circumstances by laymen or persons who do not possess any expertise. These circumstances mainly concern matters of everyday life where a person may be expected to give opinions and which opinions may be safely acted upon by others. Such circumstances cannot be definitively laid out in a closed list of cases. However, cases in which non-expert opinion has been admitted include: * Apparent age of a person * Apparent age of objects * Speed * Weather * Drunkenness * Identification of handwriting *

Eyewitness identification In eyewitness identification, in criminal law, evidence is received from a witness "who has actually seen an event and can so testify in court". The Innocence Project states that "Eyewitness misidentification is the single greatest cause of wron ...

* Identification of physical objects * The general body condition or emotional state of a person * The general condition of objects * The approximate value of objects * Approximate distance * Time * Ability to speak and understand a languageR v Decha-Iamsakun

993 Year 993 ( CMXCIII) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. Events By place Europe * Spring – The 12-year-old King Otto III gives the Sword of Saints Cosmas and Damian ...

1 NZLR 141

References

{{Reflist Evidence law