Citizen's arrest. A private citizen as contrasted with a police officer may, under certain circumstances, make an arrest, generally for a felony or misdemeanor amounting to a breach of the peace. A private person may arrest another: 1. For a public offense committed or attempted in his presence. 2. When the person arrested has committed a felony, although not in his presence. 3. When a felony has been in fact committed, and he has reasonable cause for believing the person arrested to have committed it. Calif.Penal Code, § 837.

SOURCE: Black's Law Dictionary, Sixth Edition