Legal Definitions - testimonial immunity

Testimonial immunity is a legal protection granted to a witness that prevents the government from using their compelled statements or any evidence directly derived from those statements against them in a future criminal prosecution. It is typically offered when a witness invokes their Fifth Amendment right against self-incrimination, allowing the government to compel their testimony while ensuring that the testimony itself cannot be used as a basis for prosecuting the witness.

This form of immunity is often referred to as "use and derivative use immunity." It means that while the witness must testify, neither their words nor any information discovered as a direct result of their words can be used against them. However, it does not protect the witness from prosecution if the government can prove their guilt using entirely independent evidence, meaning evidence obtained from sources completely separate from the immunized testimony.

Here are a few examples to illustrate how testimonial immunity works:

• Grand Jury Investigation: Imagine a grand jury is investigating a complex corporate fraud scheme. A mid-level manager, Ms. Chen, is subpoenaed to testify because she has crucial information about the company's financial practices. Ms. Chen is concerned that her testimony might inadvertently reveal her own minor involvement in some questionable activities, so she invokes her Fifth Amendment right against self-incrimination. To obtain her vital testimony about the larger scheme and other individuals involved, the prosecutor, with court approval, grants Ms. Chen testimonial immunity. She is then compelled to testify. Her statements to the grand jury, and any leads directly uncovered from those statements, cannot be used to prosecute her. However, if investigators later discover completely independent evidence of her wrongdoing (e.g., documents found in a separate, unrelated search, or testimony from another witness who had no knowledge of Ms. Chen's immunized testimony), she could still be charged and prosecuted based on that independent evidence.

• Congressional Hearing: A prominent executive, Mr. Davies, is called to testify before a congressional committee investigating a major data breach that exposed millions of customer records. Mr. Davies, fearing that his testimony about the company's security protocols might expose his own negligence, asserts his Fifth Amendment right. To ensure the committee can gather all necessary information to understand the breach and propose new legislation, the committee, with a court order, grants Mr. Davies testimonial immunity. He is then required to answer their questions. While his testimony before Congress cannot be used against him in any subsequent criminal proceedings, federal prosecutors could still pursue charges against him if they develop a criminal case based on evidence gathered entirely independently of his congressional testimony, such as internal company emails obtained through a separate warrant or forensic analysis reports compiled before his testimony.

• Civil Enforcement Action: The Securities and Exchange Commission (SEC) files a civil lawsuit against a brokerage firm for market manipulation. A former trader, Mr. Evans, who worked at the firm during the period in question, is called as a witness. Mr. Evans is reluctant to testify, believing his answers could expose him to criminal liability for his role in the manipulation. He invokes his Fifth Amendment right. To ensure the SEC can present a complete case against the firm, the court grants Mr. Evans testimonial immunity. He then provides detailed testimony about the firm's manipulative practices. This testimony cannot be used by the Department of Justice (DOJ) to build a criminal case against Mr. Evans. However, if the DOJ independently uncovers evidence, such as trading records from other financial institutions or confessions from other co-conspirators that do not rely on Mr. Evans' immunized testimony, they could still bring criminal charges against him.