Use immunity is a legal protection that bars federal prosecutors from using your compelled testimony, or any evidence they develop because of that testimony, against you in a criminal case. It kicks in when a court orders you to testify despite your Fifth Amendment right to remain silent. Under 18 U.S.C. § 6002, the government cannot introduce your words at trial, and it cannot use leads drawn from those words to build its case.1Office of the Law Revision Counsel. 18 USC 6002 – Immunity Generally What it does not do is make you unprosecutable. The government can still charge you — it just has to do so without touching anything connected to what you said.
The Two Layers of Protection
Federal use immunity works on two levels. The first is the obvious one: your actual testimony is off the table as evidence. The second, and the one that does most of the real work, is the ban on derivative use. Anything investigators discover by following leads from your testimony is also off-limits.1Office of the Law Revision Counsel. 18 USC 6002 – Immunity Generally
A simple example. If you tell a grand jury about a bank account where you hid money, prosecutors cannot subpoena those records and introduce them against you. If you name a co-conspirator who then agrees to cooperate, that cooperating witness is treated as tainted fruit of your immunized statements. Your words cannot become a roadmap to your own prosecution.
Federal courts have read the derivative use ban broadly. Prosecutors are not supposed to use your immunized testimony to shape investigative strategy, decide whether to charge you, or pick which other witnesses to approach. Any advantage the government might gain from hearing you talk is prohibited, including tactical and strategic uses that would never appear on an exhibit list. Without that broader reading, a prosecutor could absorb everything you said, quietly restructure the whole case around it, and then claim at trial that your testimony was never “used.”
The Supreme Court confirmed in Kastigar v. United States that this scope of protection — use plus derivative use — is “coextensive” with the Fifth Amendment privilege it replaces.2Justia. Kastigar v. United States, 406 US 441 (1972) Since the court is stripping away your right to silence, the law compensates by leaving you no worse off than if you had stayed quiet.
You Can Still Be Prosecuted — But the Bar Is High
Because use immunity doesn’t bar prosecution outright, the real question is whether the government can assemble a case using only clean, independent evidence. If you’re later charged with crimes connected to your immunized testimony, you can demand what’s known as a Kastigar hearing. You only have to show that you testified under a grant of immunity about matters related to the prosecution. That shifts the full burden to the government.2Justia. Kastigar v. United States, 406 US 441 (1972)
Prosecutors must then affirmatively prove that each piece of evidence they intend to use came from a legitimate source wholly independent of your compelled statements. Saying “we already knew about this” is not enough. The government typically has to produce sealed investigative files, dated reports, or witness logs showing the evidence existed before you ever testified. Any evidence that cannot be traced to a clean source gets suppressed. If what remains is too thin to sustain the charges, the case collapses. That is where most prosecutions of immunized witnesses fail.
Use Immunity vs. Transactional Immunity
Transactional immunity is the broader cousin. Where use immunity only restricts what evidence can be used against you, transactional immunity bars prosecution altogether for the offenses you discussed. Even if investigators later turn up airtight independent proof, no charges can be brought related to the subject of your testimony.
The federal system does not offer transactional immunity. When Congress enacted the current immunity statute in 1970, it chose use and derivative use immunity as the sole federal model.2Justia. Kastigar v. United States, 406 US 441 (1972) Some states still grant transactional immunity under their own laws. The practical difference is significant. A witness with transactional immunity walks away knowing charges are impossible. A witness with use immunity knows prosecution is still on the table; the government simply has to start from scratch.
Does Use Immunity Cross Jurisdictional Lines?
Yes, when the immunity comes from a formal court order. In Murphy v. Waterfront Commission, the Supreme Court held that the Fifth Amendment protects a federal witness against incrimination under state law, and a state witness against incrimination under federal law. If a state compels your testimony under a grant of immunity, federal prosecutors cannot use it or its fruits against you. The protection runs in both directions. One jurisdiction cannot force you to speak and then let another use your words to convict you.3Justia. Murphy v. Waterfront Commission, 378 US 52 (1964)
Who Decides to Grant Federal Use Immunity
Immunity orders are not routine. Under 18 U.S.C. § 6003, the U.S. Attorney for the district must request the order from a federal district court, and the request requires prior approval from the Attorney General, Deputy Attorney General, Associate Attorney General, or a designated Assistant Attorney General. Before asking for an order, the U.S. Attorney must find that the testimony is necessary to the public interest and that the witness has refused, or is likely to refuse, to testify on self-incrimination grounds.4Office of the Law Revision Counsel. 18 US Code 6003 – Court and Grand Jury Proceedings All requests must also be routed through the Criminal Division of the Department of Justice, which has to sign off before approval can be granted.5United States Department of Justice. 9-23.000 – Witness Immunity The multi-layered approval reflects what the government is giving up: the ability to use someone’s own words against them.
A Boundary: “Pocket” or Letter Immunity Is Not the Same
Not everything called immunity is use immunity in the statutory sense. Prosecutors sometimes offer informal protection — often called “pocket immunity” or “letter immunity” — through a written agreement, frequently tied to a plea deal or non-prosecution arrangement. These agreements operate under contract law rather than § 6002, and that difference matters.
Informal immunity does not bind other jurisdictions. State prosecutors are not parties to a federal letter agreement and have no obligation to honor it. A formal § 6002 order, backed by the Fifth Amendment analysis in Murphy, carries that cross-jurisdictional shield automatically. Testimony under a formal order is also compelled, while testimony under a pocket agreement is voluntary, so courts read the scope of pocket agreements using ordinary contract principles. Ambiguities tend to be resolved in the witness’s favor, but if the agreement explicitly lets the government make derivative use of what you say, courts will enforce that carve-out.6United States Department of Justice Archives. Criminal Resource Manual 719 – Informal Immunity Distinguished From Formal Immunity
What Use Immunity Does Not Protect You From
Immunity protects truthful testimony. It does not protect lying, stonewalling, or defying the order. Section 6002 expressly carves out prosecution for perjury, false statements, and failure to comply.1Office of the Law Revision Counsel. 18 USC 6002 – Immunity Generally Perjury under 18 U.S.C. § 1621 carries up to five years in prison and a fine.7Office of the Law Revision Counsel. 18 USC 1621 – Perjury Generally False statements under § 1001 carry the same five-year ceiling, or up to eight years if the statement involves terrorism.8Office of the Law Revision Counsel. 18 USC 1001 – Statements or Entries Generally Obstruction of justice under § 1503 can reach ten years.9Office of the Law Revision Counsel. 18 US Code 1503 – Influencing or Injuring Officer or Juror Generally
Refusing to testify once immunity has been granted carries its own consequences. The Fifth Amendment objection is gone, and the court can hold you in civil contempt under 28 U.S.C. § 1826, confining you until you comply. That confinement cannot exceed eighteen months, and it is further capped by the life of the proceeding or grand jury term.10Office of the Law Revision Counsel. 28 US Code 1826 – Recalcitrant Witnesses Courts can also pursue criminal contempt under 18 U.S.C. § 401, which authorizes fines, imprisonment, or both for disobeying a lawful order.11Office of the Law Revision Counsel. 18 US Code 401 – Power of Court Civil contempt is coercive; criminal contempt is punitive. A witness who digs in can face both.