"You have the right to remain silent" is perhaps the most recognized adage in our criminal justice system. This rule comes from the Fifth Amendment to the U.S. Constitution, which guarantees that "no person . . . shall be compelled in a criminal case to be a witness against himself." But the Fifth Amendment doesn't provide an absolute right to remain silent and not answer any questions. Rather, it protects people from having to answer incriminating questions about themselves.
A witness who is asked to provide information that could be incriminating in any way can invoke the Fifth Amendment privilege and refuse to answer. Incriminating questions require a witness to give answers that could be used to convict the witness of a crime. A question is incriminating when it calls for an answer that provides either:
But even if a witness invokes the Fifth Amendment privilege, a prosecutor can override the privilege by giving the witness immunity from prosecution in exchange for testimony.
There are two basic types of immunity from prosecution.
Transactional immunity is the broadest type of immunity; it offers complete protection from future prosecution for any matter mentioned in the immunized testimony. Because it's so broad, transactional immunity is also commonly referred to as "total" or "blanket" immunity.
Although transactional immunity offers the most protection for a witness, it doesn't prevent prosecution for criminal activities that are unrelated to something discussed in the immunized testimony. And transactional immunity isn't always available—for example, the federal system doesn't use it.
To illustrate, suppose Witness and Defendant commit an armed bank robbery. The prosecution grants Witness transactional immunity in exchange for admitting his participation in the robbery and testifying against Defendant at Defendant's trial. During his testimony, Witness reveals that he used his portion of the money stolen from the bank to purchase cocaine from Dealer.
Can Witness be successfully prosecuted for bank robbery? No. The grant of transactional immunity protects him.
Can Witness be successfully prosecuted for buying cocaine? No. Transactional immunity guarantees that Witness cannot be prosecuted for any criminal activity he discussed during his immunized testimony.
What if the prosecution learns elsewhere about a different drug purchase? If, after Witness testifies in Defendant's trial, the prosecution learns from Dealer that Witness came to him two months before the bank robbery and purchased heroin, Witness won't be so fortunate. The prosecution can charge him for that purchase because it's unrelated to the events Witness testified to: The purchase of heroin occurred before the bank robbery and was unrelated to either that crime or the cocaine purchase he mentioned.
Use and derivative use immunity is more common (used by both state and federal prosecutors) and narrower than transactional immunity. It prevents the prosecution from using the witness's statements ("use") or any evidence derived from those statements ("derivative use") against the witness in a criminal prosecution. In theory, use and derivative use immunity provides as much protection as the witness not testifying.
However, use and derivative use immunity doesn't prevent prosecutors from gathering additional, independent evidence to later use against a witness. If, while testifying, a witness gives an indication of having committed a crime and the prosecution obtains independent evidence of that crime (from a source distinct from the witness), then the witness is subject to prosecution for that crime.
For example, suppose the prosecution grants Witness use and derivative use immunity for testifying in Defendant's armed robbery trial. Witness states that after he and Defendant robbed the bank, he took some of the stolen money and used it to buy 100 kilograms of cocaine from Dealer. Witness then sold the 100 kilograms of cocaine to Buyer.
Can the prosecution get Witness for armed robbery? Yes, but the prosecution cannot use Witness's immunized testimony against him. It must rely on independent evidence that Witness robbed the bank—for example, a tip from someone who saw the crime take place.
Can the prosecution go after Witness for cocaine sale? Suppose Addict was present when Witness sold the cocaine to Buyer. Addict is later arrested and reveals that he saw this sale. In that scenario, the prosecution has proof of the sales crime from an independent source (Addict). The prosecution can use Addict's testimony to prosecute Witness for the crime.
If you've been asked to or think you should testify or otherwise cooperate with the authorities, consult an experienced criminal defense lawyer. Only such a lawyer can explain the ins and outs of immunity and otherwise protect your rights.