The gunman charged with murdering 10 people two months ago in a racist shooting spree at a Buffalo supermarket pleaded not guilty to federal hate crime charges on Monday. But Attorney General Merrick Garland still can’t seem to decide whether the government should seek the death penalty in the case.

In the eyes of the law, of course, Payton Gendron remains innocent until proven guilty. But everyone knows his guilt is not in question. Not only did numerous people at the scene see him open fire as he approached and then entered the busy store, sweeping his rifle right and left and shooting indiscriminately, but he wore a body camera and livestreamed the massacre on the online platform Twitch. When he was arrested, eyewitnesses said, he was laughing. CNN reported that he told authorities — in statements that “were clear and filled with hate” — that he had deliberately targeted the Black community. And if all that weren’t enough, he had posted lengthy screeds online detailing his murderous intentions and the elaborate preparations he had made to carry them out.

The slaughter in Buffalo was evil at its most unspeakable. If any accused murderer personifies the “worst of the worst” — the sheer, remorseless malevolence for which death is the only conceivably just punishment — it is the man who wantonly gunned down those shoppers at the Tops supermarket in May. So why is Garland hesitating? Of course prosecutors should ask for the death penalty. It would be indecent not to.

Yet suppose Gendron is sentenced to death. Then what? Even if the jury returns verdicts of guilty on all charges and then unanimously recommends that he be executed, the likelihood of the sentence ever being carried out is negligible.

Homicidal mass killers like the Buffalo gunman are almost never put to death in the United States any more. Dylann Roof, the neo-Nazi murderer who in 2015 calmly shot nine Black parishioners dead during a Bible study at the Emanuel AME Church in Charleston, S.C., was sentenced to death in 2017, and the sentence was unanimously upheld on appeal. But he remains alive today and will for the foreseeable future. So does Dzhokhar Tsarnaev, the Boston Marathon terrorist whose death penalty was upheld months ago by the US Supreme Court. So does Nidal Hassan, the Army major-turned-Islamist terrorist, who was sentenced to die by a US military court for his 2009 rampage at Fort Hood, Texas, which left 13 innocent victims dead and 32 others wounded.

A majority of Americans have long favored the death penalty for murder. According to a 2021 Pew Research Center survey, 60 percent of US adults support capital punishment even though they acknowledge the possibility of executing an innocent defendant by mistake. That support climbs even higher in the most infamous cases. In the wake of the Marathon bombing, for example, 70 percent of Americans said they supported the death penalty for Tsarnaev. Under the Constitution, even such monsters as Roof, Tsarnaev, and Hassan, whose guilt is absolutely certain, are entitled to due process of law. Yet once due process has run its course — once these depraved butchers have been fairly tried, fairly convicted, fairly sentenced to death — what justification is there for flouting the dictates of justice and disregarding what for many of us is a deep-rooted moral intuition about punishing evildoers?

On the same day that Gendron was being arraigned in Buffalo, the sentencing trial of Nikolas Cruz — the gunman who killed 17 people at a Parkland, Fla., high school four years ago — was getting underway. He too is guilty beyond any shadow of a doubt. Cruz admitted his guilt nine months ago; the sole purpose of his trial is to decide whether he should be punished with death or with life imprisonment.

Again, though — what is the likelihood of any death sentence actually being imposed on Cruz? Or on Patrick Crusius, who gunned down 23 people at an El Paso Walmart in 2019 and announced “I’m the shooter” as he was arrested? Or on Robert Bowers, the defendant charged with murdering 11 worshippers at a Pittsburgh synagogue in 2018?

In all these cases, the public devotes enormous sums of money to ensuring scrupulous impartiality in judging accused mass killers, even though their guilt is open and shut. But when the judgment so conscientiously reached is that the perpetrators should die, what almost invariably happens afterward is — nothing. A rare exception was Timothy McVeigh, who was put to death in 2001 for killing 168 people in the 1995 Oklahoma City bombing.

It has become the norm, in the wake of horrific massacres like the ones mentioned here, to expend torrents of words in heated debates about guns, racism, and mental health. Rarely is the focus directed to what ought to be society’s first priority: doing justice. It is a disgrace that barbaric assassins like Roof, Tsarnaev, and their ilk remain on death row for years, getting three square meals a day and endlessly evading the punishment that judge and jury agreed on. Perhaps one of the reasons mass killings have been multiplying is that mass killers, even when sentenced to death, go right on living.