1) You and your partner go home safely at the end of each and every shift.
2) Get the job done.
3) Liability free.
The rules are dreams, of course. The only perfectly safe way to do the job is to avoid doing it...and some officers are skilled at that, whether it is answering the call for back-up a little late or finding a quiet place to 'patrol' or getting a desk job and moving into admin. There is no way to completely avoid liability, but the triple play of making good decisions, executing the decisions properly and writing good reports works wonders...
Still, if your training, your tactics, your policies and your equipment must serve these three rules. If you're training will get you killed or sued it is BAD training. If it won't get the job done, it is BAD training.
Sometimes the order gets perverted, and this is an abomination: when fear of lawsuits stops you from doing the job or you get injured because you were more afraid of the liability bogey-man than the rusty shank... that is so very wrong.
And when the perversion gets written into policy, when an agency or administration becomes more worried about 'managing perception' than getting the basic job done, at that moment they have changed from a useful and necessary thing to a leech. It takes only that one decision to change from part of the solution to part of the problem.
Does it seem wrong and maybe insufficiently heroic to put officer safety in front of effect? It's just math. This is one that people can write into policy until the sky falls down and never effect anything... because it is physically impossible to do the job from the grave. It's not just a cop thing. Same for medics and firemen and the people trucking in food after a major natural disaster. You can't do the job dead. Worse, every cowboy who recklessly gets himself in trouble draws resources away from the original problem.
There's a line there, a balance. And, like most people, I think my line is perfect. Those who value safety more I privately think are a little cowardly. Those who value safety less I think are reckless. I never met a lot of the later.