What is it called when police cannot testify for lying?
A police officer who has lied in court before is not automatically barred from testifying, but that prior dishonesty can be used to impeach the officer’s credibility and may trigger Brady-Giglio disclosure obligations if the misconduct is material. The common shorthand in practice is a “Giglio issue” or being on a **“Brady/Giglio list.”**United States v. Giglio, 405 U.S. 150 (1972) Brady v. Maryland, 373 U.S. 83 (1963)[1]
How it works
- Brady requires disclosure of material exculpatory evidence, including evidence that can help the defense.[1]
- Giglio extends that duty to impeachment evidence affecting a government witness’s credibility, including a police officer.[1]
- Under the evidence rules, prior lies or false statements may be relevant to truthfulness, but they do not create a blanket “incompetency” to testify.[2][3]
In other words, the officer is generally still a competent witness, but their prior false testimony can be used to attack credibility and may have to be disclosed to the defense.
Plain-English term
If you are asking for the practical courtroom term, the usual answer is:
“Giglio-impaired witness” or “Brady/Giglio material.”
If you mean the formal evidentiary concept, it is:
impeachment for untruthfulness under Fed. R. Evid. 608 and, if there was a conviction for a qualifying offense, Fed. R. Evid. 609.