It was known and understood but little was done.

From Minneapolis police rendered 44 people unconscious with neck restraints in five years by Emily R. Siegel, Andrew W. Lehren and Andrew Blankstein.

The past decade and more many/most police departments have been upgrading their policies, practices and procedures, specifically to cultivate de-escalation skills, improve the odds of non-violent detentions, and otherwise become wise and safer in their interactions with the public.

After Ferguson, multiple research showed police departments were well on their way to improving their approaches and that was being reflected in declining officer-shootings and officer-caused deaths. To some people's surprise, the research indicated that African-American deaths during arrest were near proportionate to their prevalence among the crime committing population and were exceeded in deaths by whites. As of two years ago, officer deaths from black civilians have exceeded black civilian deaths from officers.

Progress is being made. Progress still needs to be made. But broadly most agree at least on the goal that officers should be safe from civilians and civilians should be safe from officers and acknowledge that frontline police have among the hardest civilian jobs.

When the first videos of George Floyd's death emerged, my first reaction was that we should be mindful of Eric Garner, Michael Brown, and Trayvon Martin. Things are never as they seem and while it is right to champion safe policing, we need full context which is rarely available.

My second response was that this looked far more like bad or ineffective training than it did like racial malice.

The substance of Siegel, Lehren and Blankstein seem to bear that out. And it was worse than I anticipated. I had assumed that Minneapolis would have dispensed with choke-hold and similar restraint techniques. They are viable and appropriate under very specific circumstances. But circumstances which rarely occur in real life. The major issue is that, with a population with a lot of comorbidities, choke-hold restraints are a significant danger to those with those comorbidities and which might not be readily discernible. Such as with Eric Garner.

Siegel et al give us the numbers.

Since the beginning of 2015, officers from the Minneapolis Police Department have rendered people unconscious with neck restraints 44 times, according to an NBC News analysis of police records. Several police experts said that number appears to be unusually high.

Minneapolis police used neck restraints at least 237 times during that span, and in 16 percent of the incidents the suspects and other individuals lost consciousness, the department's use-of-force records show. A lack of publicly available use-of-force data from other departments makes it difficult to compare Minneapolis to other cities of the same or any size.

Police define neck restraints as when an officer uses an arm or leg to compress someone's neck without directly pressuring the airway. On May 25, Minneapolis Police Officer Derek Chauvin was captured on video kneeling on the neck of a prone and handcuffed George Floyd for eight minutes — including nearly three minutes after he had stopped breathing.

Would have been nice to see the trend-line for 2015 to 2020. 44 deaths are bad but there is hope if it is a declining trend, indicating that perhaps training and policy are improving. As opposed to a flatline or, more regrettably, a rising trend.

We don't know the trend.

But the picture gets murky.

More than a dozen police officials and law enforcement experts told NBC News that the particular tactic Chauvin used — kneeling on a suspect's neck — is neither taught nor sanctioned by any police agency. A Minneapolis city official told NBC News Chauvin's tactic is not permitted by the Minneapolis police department. For most major police departments, variations of neck restraints, known as chokeholds, are highly restricted — if not banned outright.

The version of the Minneapolis Police Department's policy manual that is available on-line, however, does permit the use of neck restraints that can render suspects unconscious, and the protocol for their use has not been updated for more than eight years.

[snip]

The on-line version of the policy manual says, "The unconscious neck restraint shall only be applied … 1. On a subject who is exhibiting active aggression, or; 2. For life saving purposes, or; 3. On a subject who is exhibiting active resistance in order to gain control of the subject; and if lesser attempts at control have been or would likely be ineffective."

The passage includes a date in parentheses, April 16, 2012. The front of the manual is dated July 28, 2016.

Chokeholds have their place but they should be rare. It appears that the arrested officer was within policy when Floyd died, at least in terms of the choice of restraint.

Now it comes down to the execution of the policy. Did he use an approved technique but just executed it badly or did he not have sufficient training or was he simply negligent and lost situational awareness?

But it becomes far less cut-and-dried.

Ed Obayashi, an attorney and the deputy sheriff in Plumas County, California, is a national use-of-force expert who trains and advises California police agencies. He said police departments across the country have been moving away from the neck restraint option for many years because of its "inherent life-threatening potential" and because officers often misinterpret resistance by a suspect, who may simply be struggling to breathe.

"It's common sense," Obayashi said. "Any time you cut off someone's airway or block blood flow to the brain, it can lead to serious injury or death as we have seen in so many of these tragedies. By using this tactic, it's a self-fulfilling tragedy."

Obayashi said it's notable that the Minneapolis Police Department policy on neck restraints appears to be dated and said that rather than discouraging or generally prohibiting the tactic, its policy language is consistent with a permissive stance.

At the higher level, perhaps we are not making as rapid progress in improving policies and training as I had been observing in the humbers.

Tragic as Floyd's death was, it seems, if the reporting is correct, that the arrested officer was using a still approved and commonly used technique for restraint. Whatever we think about the degree of the police officer's guilt, it seems as if the Police Department itself is an unindicted co-conspirator.