This is an idiom that refers to the death of an innocent person. Alternate translation: "a person who does not deserve to die" (See: [[rc://en/ta/man/jit/figs-idiom]])
The Jewish leaders use this question to emphasize that they do not care about what Judas said. Alternate translation: "That is not our problem!" or "That is your problem!" (See: [[rc://en/ta/man/jit/figs-rquestion]])