NASHVILLE (AP) — A Tennessee death row inmate who has always claimed innocence asked the governor on Monday to commute his sentence to life in prison.

Pervis Payne is scheduled to die on Dec. 3 for the 1987 stabbing deaths of Charisse Christopher and her 2-year-old daughter, Lacie Jo. Christopher's son, Nicholas, who was 3 at the time, was also stabbed but survived. Payne, who is Black, told police he was at Christopher's apartment building to meet his girlfriend when he heard the victims, who were white, and tried to help them. He said he panicked when he saw a white policeman and ran away.

A Memphis judge last month ordered DNA testing of a knife and other evidence in the case. At the time of Payne's trial, DNA testing of evidence was unavailable, and no testing has ever been done in his case.

A petition Payne's lawyers sent to Gov. Bill Lee on Monday asks the governor to at least postpone his execution until lawmakers can fix a loophole that prevents him from presenting evidence of intellectual disability in court.

The U.S. Supreme Court has ruled that executing an intellectually disabled person violates the Eighth Amendment's prohibition on cruel and unusual punishment, and Tennessee has its own law forbidding the execution of the intellectually disabled. However, the law does not contain a mechanism for people to reopen their cases if they were sentenced before it went into effect.