No decent citizen could fail to be appalled by the video, released Friday, showing Memphis police officers beating a 29-year-old Black man, Tyre Nichols, so badly on Jan. 7 that he died three days later. No feeling citizen could fail to be moved by the anguish of his mother, RowVaughn Wells, as she eloquently described her grief at losing a young man, himself the father of a 4-year-old, who cried out for “mom” as he absorbed the assault. And no concerned citizen can fail to be impressed by, and appreciative of, the way in which those who justifiably protested Mr. Nichols’s death heeded — with sporadic exceptions — Ms. Wells’ call for nonviolence.

Yet no thinking citizen can fail to be frustrated that something like this could have happened less than three years after George Floyd died at the hands of Minneapolis police officers, triggering a national movement for police reform and social justice — or, for that matter, nearly 32 years after Los Angeles police officers delivered an eerily similar, though nonfatal, beating to Rodney King. How many more times will Americans, and their leaders in government and law enforcement, vow “never again” about such an incident, only to find ourselves ruefully saying, “Once again.”

Legal accountability for alleged police perpetrators is indeed necessary, to punish, to deter and to reinforce the principle that those who wear the badge are not above the law. The sobering reality, though, is that such retrospective justice is no panacea. If it were, guilty verdicts in Floyd’s case would have prevented what happened in Memphis. So would the convictions, in 1993, on federal civil rights charges, of two officers who beat Rodney King — albeit after a jury acquitted them the previous year, sparking six days of violent protest in L.A.

Further reforms are needed to reduce police impunity, including federal legislation to modify the “qualified immunity” doctrine, largely created by the Supreme Court, that often blocks lawsuits for unconstitutional abuses. Still, even many oft-proposed reforms — including some included in the George Floyd Justice in Policing Act — would not have prevented what happened to Mr. Nichols. The measure bans potentially deadly chokeholds, for example, but that appears to be one of the few forms of physical force the officers in Memphis did not visit upon Mr. Nichols’ body.

Indeed, Memphis, similar to other cities, had instituted reforms. One was the use of police body cameras to record encounters with citizens, which seemingly did not give the officers who beat Mr. Nichols much pause. Another was the recruitment of a force that reflects the city’s large Black majority. All five officers who assaulted Mr. Nichols were Black — as is the chief, Cerelyn Davis. Memphis hired her in 2021 after a career in Durham, N.C., during which she had embraced the protests over Floyd’s murder and decried “systemic racism” in U.S. policing.

In the wake of Tyre Nichols’ death, the Memphis police have nothing to celebrate and much to improve. The same goes for the United States as a whole.

* Guest editorial excerpt by The Washington Post.