Legal testimony

In the law, testimony is a form of evidence that is obtained from a witness who makes a solemn statement or declaration of fact. Testimony may be oral or written, and it is usually made by oath or affirmation under penalty of perjury. Unless a witness is testifying as an expert witness, testimony in the form of opinions or inferences is generally limited to those opinions or inferences that are rationally based on the perceptions of the witness and are helpful to a clear understanding of the witness' testimony.

Eyewitness testimony
Psychologists are interested in the many factors that shape the testimony of people in the courtroom.

Expert testimony
An expert witness may give opinion about facts and conclusions within his or her field of expertise, in addition to direct evidence.