You are absolutely wrong. Not just incorrect, but wrong. When stakes are highest, so is the absolute need for the absolute highest level of professionalism, and integrity and accuracy, with a goal of zero errors. Even if the goal is not 100% obtainable, it still must be the goal. Because the stakes are so high. Note: when someone is killed 'accidentally' or in any manner which is avoidable or not completely justifiably, with no tortured justifications, there is a grave loss not just in loss of life of that one person killed but a grave loss to the public in their ability to trust and rely upon the police and law enforcement and the legal justice system. Every single death caused by police action or negligence erodes the confidence and integrity of law enforcement, to the detriment of every citizen and society as a whole.
This is about the medical industry, but it pertains to law enforcement as well:
http://qsen.org/faculty-resources/videos/chasing-zero-winning-the-war-on-healthcare-harm/
I agree with your sentiment.. the goal should indeed be zero error. This, of course, like any other human process, is impossible... but is definitely a good goal.
Where I disagree, is that it is not the act of a mistake being made by a cop that is causing the issue of lack of confidence, etc.. It is the media taking a situation where a raving lunatic was threatening the lives of many people, had a history of violence and drug use, and got himself shot for assaulting a cop, and issue a headline (which is as far as the vast majority of people read) that says, "innocent black man minding his own business, saving kittens from trees, gunned down by evil white cops trying to steal his money for drugs" - click HERE to read more about it and click on all of our ads too!
that is the real problem.