Actually I suspect this won’t go anywhere - I recall a story that reached HN a few years ago from the (I think) N.Y. subway where a wanted criminal attacked (and stabbed) someone and the police literally just stayed on the other side of a door while watching and doing nothing. The attacker was eventually subdued by the other passengers. When they were taking to court they were found to have done nothing wrong: the opinion said something along the lines of “police are not required to intervene”, eg stopping attempted murder is apparently not part of their job requirements. Yet they have tasers and guns “to stop crime”
It seems we’ve gotten pretty far already without it - but it’s an open question.