Immunity from prosecution can be revoked in some situations and not in others, and the difference turns on how the immunity was granted. Statutory immunity issued through a federal court order cannot be revoked at the government’s choice, but the statute itself always allowed prosecution for perjury or false statements made under the grant. Informal immunity from a cooperation agreement or proffer letter is a contract, and the government can treat it as void if the witness breaches. And even when immunity stays in place, prosecutors can still bring charges for the underlying crime if they build the case entirely from evidence independent of the compelled testimony.
Statutory Immunity Is Not Revocable, But It Was Never Unlimited
Federal immunity granted by court order is use and derivative use immunity. The government cannot use your compelled testimony, or any evidence derived from it, against you in a criminal case.1Office of the Law Revision Counsel. 18 USC 6002 – Immunity Generally That protection kicks in automatically once the court’s order issues; no separate agreement is signed, and the government has no mechanism to withdraw it later because you became inconvenient or uncooperative.
What people often describe as “revocation” is really the statute’s built-in exception. The text of 18 USC 6002 explicitly carves out perjury, giving a false statement, and failing to comply with the order. If you lie under a grant of statutory immunity, the government can charge you with perjury and use the immunized testimony itself to prove the lie.1Office of the Law Revision Counsel. 18 USC 6002 – Immunity Generally That exception was a condition from day one, not a punishment imposed after the fact. You never had protection against a perjury charge in the first place.
For the underlying crime you were testifying about, the core protection generally stays intact even if you lied. The government still cannot use your compelled testimony or its fruits to prosecute those original offenses. It would have to build that case from wholly independent evidence.
Cooperation Agreements and Proffer Letters Can Be Voided
Most real-world situations people think of as revocation involve informal immunity, not the statutory kind. Prosecutors routinely negotiate cooperation agreements, sometimes called letter immunity or non-prosecution agreements, in which the witness promises truthful information and the government promises not to prosecute. These are contracts and follow contract principles.
When a witness breaches by lying, withholding information, or committing new crimes, the government can take the position that the deal is void. The protections in a cooperation agreement exist only because both sides are performing. A breach can release the government from its promise not to prosecute, and depending on the agreement’s terms, the statements the witness made during cooperation may become usable against them.
Proffer agreements, sometimes called “queen for a day” sessions, give even thinner cover. In a typical proffer, you share information with prosecutors in an informal meeting. The government generally agrees not to use those statements in its direct case at trial but reserves the right to use them for other purposes, such as impeaching your testimony if it later contradicts the proffer, or developing leads. If no full cooperation deal follows, the proffer offers minimal shelter.
You Can Still Be Prosecuted Even With Immunity Intact
Use and derivative use immunity does not make you unprosecutable for the underlying offense. The Supreme Court held in Kastigar v. United States that this form of immunity is co-extensive with the Fifth Amendment privilege, which means the government can still bring charges as long as it carries an “affirmative duty to prove that the evidence it proposes to use is derived from a legitimate source wholly independent of the compelled testimony.”2Justia US Supreme Court. Kastigar v United States, 406 US 441 (1972)
In practice this happens at a Kastigar hearing. The defendant shows that they testified under immunity about matters related to the prosecution. The burden then shifts to the government to demonstrate, for each piece of evidence, that it came from a legitimate independent source. The standard is demanding, and prosecutors who were exposed to immunized testimony often have difficulty proving their investigation was not shaped by what the witness said.
One boundary worth flagging: transactional immunity, which blocks prosecution for the offense entirely regardless of independent evidence, is no longer available under federal law. Some states still offer it, so if your grant came from a state proceeding, the rules there may be broader.
Waiver Is a Separate Way to Lose Protection
You can also lose immunity by giving it up. An explicit waiver happens when a witness signs a written document relinquishing the protection. An implicit waiver can occur when someone who previously received immunity makes voluntary statements to law enforcement without asserting the privilege, or chooses to testify without invoking the Fifth Amendment. Once immunity is waived, the prosecution can use the previously protected testimony against you.
Waiver differs from revocation because you initiate it rather than having protection stripped away. Courts examine whether a waiver was truly voluntary, since the consequences are severe.
What This Means If You Have Immunity
If your immunity came from a federal court order under 18 USC 6002, your protection is more durable than most people assume. The government cannot simply take it back. It can charge you with perjury and use the immunized statements to prove it, and it can prosecute the underlying crime using independent evidence, but the core bar on using your compelled testimony for the original offense remains unless you waive it.
If your immunity comes from a cooperation agreement or proffer letter, your position is more fragile. Those protections are only as strong as your compliance with the terms. Lying, holding back information, or picking up new charges can give the government grounds to walk away from its promises and, in some cases, to use your own words against you. Before signing a cooperation agreement, know exactly what triggers a breach and what the government is permitted to do with your statements if the deal falls apart.