In a non-jury trial the fact-finder is one or more professional judge

Judge

A judge is a person who presides over court proceedings, either alone or as part of a panel of judges. The powers, functions, method of appointment, discipline, and training of judges vary widely across different jurisdictions. The judge is supposed to conduct the trial impartially and in an open...

s rather than a jury

Jury

A jury is a sworn body of people convened to render an impartial verdict officially submitted to them by a court, or to set a penalty or judgment. Modern juries tend to be found in courts to ascertain the guilt, or lack thereof, in a crime. In Anglophone jurisdictions, the verdict may be guilty,...

 of the defendant

Defendant

A defendant or defender is any party who is required to answer the complaint of a plaintiff or pursuer in a civil lawsuit before a court, or any party who has been formally charged or accused of violating a criminal statute...

's 'peers'.

In common law

Common law

Common law is law developed by judges through decisions of courts and similar tribunals rather than through legislative statutes or executive branch action...

 jurisdictions, all trials in equity, of petty criminal offenses and violations, and of small claims at law are non-jury trials, also known as bench trial

Bench trial

A bench trial is a trial held before a judge sitting without a jury. The term is chiefly used in common law jurisdictions to describe exceptions from jury trial, as most other legal systems do not use juries to any great extent....

s, held before a single judge. In all other cases, whether criminal charges and civil claims at law, the defendant may also waive a jury and be subject to a bench trial.

In civil law

Civil law (legal system)

Civil law is a legal system inspired by Roman law and whose primary feature is that laws are codified into collections, as compared to common law systems that gives great precedential weight to common law on the principle that it is unfair to treat similar facts differently on different...

 systems where juries are unknown, all trials are held before a judge or panel of judges.

Judges in non-jury trials serve dual roles, ruling on applicable law, including the rules of evidence

Evidence (law)

The law of evidence encompasses the rules and legal principles that govern the proof of facts in a legal proceeding. These rules determine what evidence can be considered by the trier of fact in reaching its decision and, sometimes, the weight that may be given to that evidence...

 and procedure, and as finders of fact. While lay juries are not trusted to be exposed to prejudicial inadmissible evidence, which may be grounds for a mistrial, judges in a non-jury trial may review all proffered materials while excluding from consideration any evidence that they determine to be inadmissible under the law.