Republican and Democratic politicians alike — including the state’s former attorney general Kamala Harris, now running for president — refused for years to allow advanced DNA testing in Cooper’s case, even though his lawyers would have paid for it. (Harris has apologized and says she now favors testing.) This summer crucial evidence from Cooper’s case is finally being subjected to that testing, 36 years after the murders. We may know the results by September.

DNA testing accounts for many of the 165 exonerations and prison releases because of dubious evidence since 1973, by the count of the Death Penalty Information Center.

Usually, though, there isn’t DNA available that can be tested to determine guilt or innocence. As in the Clifford Williams case, it’s more murky. The crucial evidence in his conviction came from an eyewitness who may have been a pathological liar.

But let’s be clear: The great majority of people executed are guilty. They have frequently killed with the utmost savagery.

Scotty Morrow, a black man from Georgia, indisputably committed a brutal murder in 1994. He fought with his ex-girlfriend, Barbara Ann Young, and, as her 5-year-old son watched, shot her in the head and killed her.

Morrow also shot dead another woman in the house, Tonya Woods, and shot a third woman, LaToya Horne, in the face. Horne was able to stagger down the road before collapsing. She suffered permanent injuries.

Not surprisingly, Morrow was sentenced to die — but let me throw in a bit of complexity.

Morrow grew up in a violent home where he was raped and beaten as a child, and he never received mental health support to deal with his trauma; that justifies nothing but may help explain something. He desperately wanted to reconcile with Young, and when told that she had been exploiting him for money while she waited for her “real man” to return from prison, he “just snapped,” as he put it. After the murders, he prepared to commit suicide but was arrested; he then prayed daily for 25 years for the families of the women he had killed.

Image An undated booking photo from the Georgia Department of Corrections shows Scotty Morrow, a death row inmate. Credit... Agence France-Presse — Getty Images

“Rarely in my career as a prosecutor and a judge did I witness this level of remorse and acceptance of responsibility,” reflected Judge Wendy Shoob, one of the judges who dealt with Morrow’s appeals over two decades. The only disciplinary report against him in a quarter-century in prison was for intervening in a fight to protect an inmate who was being stabbed with a shank. Several correctional officers wrote letters appealing that his life be spared.

“Scotty Morrow is literally the only inmate I would do this for,” said a correctional officer with 16 years in law enforcement, Nathan Adkerson. Sgt. Tajuana Burns described him as “just a really nice man.” Lindsey Veal Jr., a mental health counselor, said Morrow “actually makes the prison safer,” and added: “There are very few inmates I can call fully rehabilitated. But, without question, Scotty is one of them.”

William L. Buchanan , a psychologist who worked with Morrow, recalled that one correctional officer “looked me straight in the eyes and stated to me, ‘This is the best man in the world.’”

Yet in the end the State of Georgia did with meticulous planning what Morrow had done impulsively in a spasm of fury. It executed him last month by lethal injection. In his last moments in the execution chamber, Morrow apologized again to the families of the women he had killed, adding to the 20 witnesses: “I’m truly sorry for all that happened. I hope that you all recover and have healing.”

Was the man strapped down on a gurney truly the same person as the enraged brute who had shot dead Young and Woods 25 years earlier?

The death penalty has been applied to at least 222 crimes in the Anglo-American legal system, including marrying a Jew and stealing a rabbit. For a time in America, stealing grapes was punishable by death. So was witchcraft, as we know from the Salem trials.

For centuries executions were public affairs . The last public execution in the United States was in August 1936 in Owensboro, Ky. Perhaps 20,000 people gathered to see a black man, Rainey Bethea, 22, hanged for the rape and murder of a white woman. The carnival atmosphere and “hanging parties” led Kentucky to ban public executions, although public lynchings continued.