A grand jury subpoena is a written order for you to go to court and testify about information you may have.
If a law enforcement officer threatens to get a subpoena, you still do not have to answer the officer’s questions right then and there, and anything you do say can be used against you. The officer may or may not succeed in getting the subpoena. If you receive a subpoena or an officer threatens to get one for you, you should call a lawyer right away. If you are given a subpoena, you must follow the subpoena’s direction about when and where to report to the court, but you can still assert your right not to say anything that could be used against you in a criminal case.