An officer who, is a member of a court martial. 2. His duties are to prosecute in the name of the United States, but he shall so far consider himself as counsel for the prisoner, after the prisoner shall have made his plea, as to object to leading questions to any of the witnesses, or any question to the prisoner, the answer to which might tend to criminate himself. He is further to swear the members of the court before they proceed upon any trial.