Legal Definitions - falsus in uno doctrine

Definition: Falsus in uno doctrine (fal-suh-s in yoo-noh) is a Latin principle that means "false in one thing, false in all." It is used in the legal system to determine the credibility of a witness's testimony. If the jury believes that a witness intentionally lied about a material issue, then the jury may disregard all of that witness's testimony.

Example: During a trial, a witness testifies that they saw the defendant commit the crime. However, upon cross-examination, it is revealed that the witness was not present at the scene of the crime and was lying about their testimony. The falsus in uno doctrine would allow the jury to disregard all of the witness's testimony, including their identification of the defendant as the perpetrator.

Explanation: The example illustrates how the falsus in uno doctrine can be applied in a legal setting. If the jury believes that a witness intentionally lied about one aspect of their testimony, then the jury may question the credibility of the witness's entire testimony. This principle is used to ensure that witnesses are truthful and that the legal system is fair and just.