https://www.techdirt.com/articles/20211219/09111448146/dc-metro-pds-powerful-review-panel-keeps-giving-bad-cops-their-jobs-back.shtml

After bad cops do bad things, other cops will rush to the defense of the agency employing them, claiming most cops are good and these officers are outliers. These assertions might be more believable if law enforcement agencies (and their unions) didn't regularly cover for bad officers or, in the case of police unions, work tirelessly to ensure bad cops get their jobs back.

Everything works in favor of bad cops. Their union reps can force agencies to rehire them. Fellow officers look the other way or falsify reports to cover for their actions. Oversight boards are neutered, ignored, and obstructed. Police officials with the power to rid agencies of bad officers either refuse to do so or are powerless in the face of restrictive union contracts.