Witness immunity

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Witness immunity from prosecution occurs when a prosecutor agrees not to prosecute a witness in exchange for testimony or production of other evidence.

In the United States, the prosecution may grant immunity in one of two forms. Transactional immunity, colloquially known as "blanket" or "total" immunity, completely protects the witness from future prosecution for crimes related to his or her testimony. Use and derivative use immunity prevents the prosecution only from using the witness's own testimony or any evidence derived from the testimony against the witness. However, if the prosecutor acquires evidence substantiating the crime independently of the witness's testimony, the witness may then be prosecuted.

Prosecutors at the state level may offer a witness either transactional or use and derivative use immunity, but at the federal level, use and derivative use immunity is much more common.^{[citation needed]}

In the United States, Congress can also grant criminal immunity (at the Federal level) to witnesses in exchange for testifying.^[1]