. . . from the article in my above comment :

"Part of the problem is the lack of centralized, specific guidance," says Seth Stoughton, a former police officer who now specializes in questions of police use-of-force at the University of South Carolina Law School.

"But I don't think that's the entire problem," he said. "I think part of the problem is also a very strong cultural resistance to criticizing other cops."

I am reminded of the Tenerife crash :

[en.wikipedia.org]

. . . still the largest loss-of-life airline crash.

In that incident, one of the major causes was the culture of pilots who were very reluctant to question/criticize the senior pilot(s).