Legal Definitions - perjury-trap doctrine

The perjury-trap doctrine is a legal principle that states that if a person is called as a witness in a grand-jury investigation and the prosecution secures a perjury indictment against them based on their testimony, the indictment must be dismissed if the person's testimony did not relate to the ongoing investigation.

For example, if a person is called to testify before a grand jury investigating a drug trafficking ring and is asked about their personal finances, and then later indicted for perjury based on their answer, the perjury-trap doctrine would apply. Since the question about personal finances was not material to the ongoing investigation, the perjury indictment would be dismissed.

The perjury-trap doctrine is meant to protect witnesses from being unfairly targeted for perjury charges and to ensure that grand-jury investigations are focused on relevant issues.