Elijah McClain, a 23-year-old massage therapist, had broken no law, carried no weapon and posed no threat. It is an unspeakable outrage that the police in Aurora, Colo., near Denver, stopped him last summer, manhandled him and ultimately caused or helped cause his death. The fact that those officers continue on the force — unprosecuted, unpunished and, to all appearances, unaccountable — is yet another symptom of the systemic sickness in American policing and justice.

Mr. McClain was a black man, slightly built, 5 foot 7 inches tall. His “crime” was to look and act unusual — he wore a mask, owing to a blood condition that made him prone to cold, and waved his arms as he walked down the street, on an errand to fetch iced tea for a family member.

“I have a right to stop you because you’re being suspicious,” said one of the officers. And then it all started — Mr. McClain’s indignant, panicked response and resistance; the officers’ hair-trigger reaction and use of force; their tackle that slammed him to the ground; the headlock that impeded blood to his brain; the shot of a sedative, ketamine, from paramedics, that left him limp; his cardiac arrest en route to the hospital; and, three days later, the decision to remove life support after he was declared brain-dead.

In the course of the encounter, which spun out of control in seconds, Mr. McClain sobbed and pleaded with the officers — “I’m just different,” he said. They weren’t interested; they didn’t listen.

Dave Young, the district attorney in Adams County, declined to bring charges against the police, concluding there was “no reasonable likelihood” that he could secure a conviction. Colorado Gov. Jared Polis (D) has now named the state’s attorney general as a special prosecutor to revisit the case and that decision.

The attorney general, Phil Weiser, should focus on several disturbing questions. Why were Aurora police still allowed to place Mr. McClain in a chokehold — a policy they have since rescinded — when many departments elsewhere have prohibited that practice? Why did paramedics inject Mr. McClain with 500 milligrams of ketamine, known popularly as “Special K,” an anesthetic sometimes considered a date-rape drug because of its ability to incapacitate subjects and leave them in a dreamlike state? Was that in any way a justified intervention in the case of a man who was walking down the street, minding his own business, when police showed up? What is the mortality rate in unwilling subjects to whom ketamine is administered?

Finally, what sort of training do police undergo that would lead them to escalate so quickly what should have been an inconsequential encounter — and, in a city and surrounding county that are overwhelmingly white, does that training include instruction on implicit racial bias?

The niceties in the Adams County coroner’s report — which left Mr. McClain’s exact cause of death undetermined, but mentioned his physical exertion as a likely contributing factor — did more to obscure than enlighten. The basic fact is that Mr. McClain did not deserve to die and would not have, if police had exercised their job with competency and compassion.

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