Josephus, Antiquities 20: The death of James, brother of Jesus who was called Christ, under High Priest Ananus — a non-Christian, undisputed historical source

Josephus (first-century Jewish historian, not Christian) writes about High Priest Ananus (Annas the younger) who, during the gap between Roman governors (Festus had died, Albinus was en route), convened the Sanhedrin and brought before it "the brother of Jesus who was called Christ, whose name was James" and others on charges of breaking the law, condemned them to be stoned. This caused outrage among "the most equitable citizens" who complained to King Agrippa, resulting in Ananus being removed from office. Mike emphasizes: (1) this is how Josephus introduces figures by association with better-known individuals — James introduced through Jesus, not the reverse; (2) this is not disputed by scholars as a Christian interpolation; (3) Josephus wrote roughly 500 words per year of history, so this event was significant enough to merit inclusion as part of a political narrative about Ananus.