Fact-finder Definition

fact-finder
noun
The person or persons in a particular trial or proceeding with responsibility for determining the facts. The jury typically acts as the fact-finder in any case where there is one; otherwise, the judge will perform that function along with that of making determinations of law.
Webster's New World Law

One who finds facts.

Wiktionary

(law) In a legal proceeding, the person or persons given the task of weighing all evidence presented and determining the facts of the case in light of that evidence; the jury, or where there is no jury, the judge.

Wiktionary

(law) The person or persons (such as jurors or judges) who consider evidence in a legal proceeding and make determinations on assertions of fact.

Wiktionary