A trier of fact, also known as a fact-finder, is an impartial person or group of people responsible for determining factual issues in a legal proceeding. In personal injury claims, the trier of fact is responsible for determining liability and damages. The trier of fact must weigh the evidence admitted against the burden of proof, usually a preponderance of the evidence in civil claims, or whether the incident is "more likely than not" to have occurred as the plaintiff or defendant alleges.

In a personal injury claim, a trier of fact may be:

• A judge in a bench trial
• A jury in a jury trial, which applies the facts as they find them to the relevant statute as instructed by the judge
• A mediator in a mediation, whose judgment is not binding but tries to help both sides see the case objectively

In court proceedings, there is a distinction between questions of fact and questions of law. A judge is always the one who resolves questions of law, such as how a certain law is interpreted or which laws should be applied to a certain case. The trier of facts, meanwhile, only evaluates questions of fact, such as the strength of the evidence, witness credibility, whether the defendant is liable for any damages and, if so, how much the plaintiff shall be awarded.