An ecclesiastic with power to sit in judgment and to pronounce sentence.
The bishop is the ordinary judge in his diocese for all cases not withdrawn from his authority by common law.
While the bishop may act as judge in matters subject to him, he is recommended to allow the officialis or chief justice to try cases together with the associate justices.
All judges appointed by the bishop take an oath on assuming their office and should be above suspicion and be well versed in canon law.
Some cases require five judges, others three, and some only one.
Sentence is pronounced by majority vote.
The judge of appeal from a diocesan court is the archbishop's court, or the Rota, in Rome.
New Catholic Dictionary