Within the adversarial system, judges and juries function as fact-finders – that is, as those who, having heard the arguments both for and against a particular construction of the facts of a case, are called upon to decide whether the construction of the facts presented by the prosecution (in a criminal trial) reaches an appropriate level of certainty: beyond reasonable doubt. Fact-finders are concerned with the truth of the matter at issue – whether, for example, given the evidence and arguments, it is the case that Smith embezzled the funds of Alpha Inc. or assaulted Bill Bloggs. However, because the determination of truth is the basis for the just disposition of a case, fact-finders may be said to be concerned with justice as well as truth.

But judges do not always function as fact-finders. In jury trials they do not. In the US criminal justice system, in serious cases defendants have a right to a jury trial, and in those cases, the judge who presides over a case will function as a “master of ceremonies” and interpreter of the law. Presiding judges also have a critical role in determining that the trial is fair and (with varying degrees of discretion) making sentencing decisions should the defendant be found guilty.