Why It Matters
Witnesses subpoenaed by Congress can lawfully decline to answer questions by invoking the Fifth Amendment privilege against self-incrimination. The Supreme Court has consistently upheld that protection in the legislative setting, according to the Congressional Research Service Manual updated March 27. The privilege covers any testimony a witness reasonably believes could be used against themselves in a prosecution, or that could lead investigators to other incriminating evidence.
The issue keeps surfacing before committees. Former White House physician Kevin O'Connor cited the privilege, along with doctor-patient confidentiality, when he declined to testify before the House Oversight and Government Reform Committee on July 9, 2025, as part of its inquiry into former President Joe Biden's mental fitness in office. Dr. Anthony Fauci followed a similar path in July, invoking the privilege more than 100 times before the Senate Homeland Security and Governmental Affairs Committee. Years earlier, Jeffrey Clark, Roger Stone, and Michael Flynn each pleaded the Fifth throughout their depositions before the House select committee investigating the January 6 attack on the U.S. Capitol.
The Big Picture
The central question in any Fifth Amendment dispute before Congress is whether the requested testimony would be incriminating. Courts have read that standard broadly, extending the privilege to any statement a witness reasonably believes could expose them to prosecution, even indirectly. A witness need not use any particular words to invoke it, only language a committee could reasonably understand as an attempt to claim the privilege. Blanket refusals to answer every question, though, generally draw closer scrutiny than objections raised one question at a time.
That flexibility carries a duty for committees, too. In Quinn v. United States, the Supreme Court threw out a contempt conviction because the committee never clearly overruled the witness's objection or directed him to answer. The witness, the Court found, had no fair notice that his silence could lead to prosecution. Committees that want to compel an answer over a privilege claim must make that demand explicit.
Congress isn't powerless against a valid claim. Under 18 U.S.C. § 6005, a chamber majority or a two-thirds committee vote can seek a federal court order compelling testimony in exchange for immunity. The Attorney General is entitled to at least 10 days' notice and can request a 20-day delay before the order takes effect. Testimony given under such an order can't be used against the witness in a later prosecution, except for perjury or false statements tied to that testimony.
The privilege isn't just limited to congressional witnesses. President Donald Trump invoked it more than 440 times during a 2022 deposition tied to New York Attorney General Letitia James's civil probe into the Trump Organization's business practices, a reminder that the same protection extends well beyond Capitol Hill. A presidential pardon complicates that picture further. It generally eliminates the privilege for the pardoned offense, since federal prosecution is no longer possible. It doesn't reach unrelated crimes, though, and it doesn't shield a witness from state prosecution for the same conduct.
The Bottom Line
None of this gives Congress a free hand. The privilege still forces committees to choose between accepting a witness's silence and taking the harder, more deliberate step of seeking immunity to get answers on the record, a trade-off that will keep shaping how far high-profile investigations can actually reach.
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