Fifth Amendment, the
a part of the Constitution of the United States which says that you do not have to give information in a court of law which could be used against you, and that you cannot be put in prison or have your property taken away without a proper legal trial
to refuse to give information against yourself in a court of law. People in the US sometimes use this expression humorously when they do not want to answer a question.:
plead/take the Fifth (Amendment)
• "I plead the Fifth", Jack said, when his wife wanted to know where he had been.