FAQ

A: When federal prosecutors seek information from a witness or a target, they can extend certain protections to facilitate cooperation. Three common frameworks are proffer letter immunity, letter immunity, and statutory immunity. Although they are often discussed together, they differ in source, scope, and practical effect. Here is a clear overview to help you distinguish them.

A: A proffer session—sometimes called a “queen for a day” meeting—typically proceeds under a written proffer agreement. In general terms, the agreement limits how the government may use the witness’s statements from that meeting. The protection is usually qualified: it restricts direct use of the statements in the government’s case-in-chief but permits use for impeachment, leads, or under specified exceptions. Because the terms are contractual, the precise protections depend on the language of the letter that counsel and the government execute in advance of the session. Proffer protections do not bar prosecution; rather, they set ground rules for how the statements may be used if a case proceeds.

A: Letter immunity refers to a prosecutor’s written assurance that, if the witness provides truthful cooperation as agreed, the government will not prosecute for specified conduct or will limit charges accordingly. Unlike a proffer letter, which governs use of statements, letter immunity addresses charging discretion. Its scope is defined by the letter itself, including any conditions, carve-outs, or requirements of continued truthful cooperation. Because it is a discretionary commitment by the prosecution, its protection turns on compliance with the letter’s terms and the authority of the issuing office.

A: Statutory immunity is conferred by operation of law, typically upon approval and issuance of an immunity order. It compels testimony and, in exchange, provides defined protections. Its scope and effect are set by statute and court order rather than by agreement with the prosecutor. Statutory immunity is formal, with procedures and conditions prescribed by law, and it is distinct from negotiated letters. It addresses the use of compelled testimony and the government’s ability to prosecute thereafter, according to the statutory framework in effect.