MBE Rules · Criminal Procedure
Use and Derivative-Use Immunity
Kastigar v. United States
The rule
Use-plus-derivative-use immunity is coextensive with the Fifth Amendment and compels testimony; a later prosecution requires the government to prove all evidence derives from wholly independent sources.
In plain English
Use and derivative-use immunity protects a witness from having their testimony used against them in a criminal case, as well as any evidence derived from that testimony. This means that if the government wants to prosecute someone based on information obtained through compelled testimony, they must show that the evidence was obtained from sources that are completely independent of that testimony.
Worked example
A witness is compelled to testify about a drug deal under a grant of use and derivative-use immunity. During the testimony, the witness reveals the location of a stash house. Later, the government finds drugs at that location and tries to prosecute the witness. However, they must prove that the evidence was obtained from an independent source, not from the compelled testimony, to proceed with the case.
Memory hook
Immunity means what you say can't be used against you or lead to your prosecution.
The trap
Exams may present scenarios where students confuse use immunity with transactional immunity, leading them to overlook the nuances of derivative-use protections. Students might also misinterpret the burden of proof regarding independent sources.
How examiners test it
Questions often involve a witness who has been granted immunity and then detail subsequent evidence obtained, testing the student's understanding of the limits of that immunity and the government's burden in prosecution.
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