Simple English definitions for legal terms
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Perjury-trap doctrine: This means that if someone is called to testify in front of a grand jury and the prosecutor is only trying to get evidence to charge them with perjury (lying under oath), then any charges for perjury should be dismissed. This is especially true if the person's testimony has nothing to do with the main investigation the grand jury is working on.
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.