A trier of fact, or finder of fact, is a person, or group of persons, who determines facts in a legal proceeding, usually a trial. To determine a fact is to decide, from the evidence, whether something existed or some event occurred. Various aspects of a case that are not in controversy may be the "facts of the case" and are determined by the agreement of the separate parties; the trier of fact need not decide such issues.

Juries

In a jury trial, a jury is the trier of fact. The jury finds the facts and applies them to the relevant statute or law it is instructed by the judge to use in order to reach its verdict. Thus, in a jury trial, the findings of fact are made by the jury while the judge makes legal rulings as to what evidence will be heard by the jury and what legal framework governs the case. Jurors are instructed to strictly follow the law as given by the judge, but are in no way obligated to do so. In some cases this amounts to jury nullification, e.g. the jury effectively re-writing the law or blatantly ignoring it in a particular case.