> Authorities have to conduct investigations.

There's more than one way to do that, some a lot better than the current practice which, as of now, involves shooting suspects in the head.

> Since investigators can't consult a magic ball

That's what the shooting perpetrators claim too - "we weren't sure if this woman was going to try to wipe us all out, we've got no magic ball, thus, head meet bullet seemed like a reasonable thing to do... repeatedly".

> One can attempt the ideal

There's no evidence that anything close to that has been attempted since at least 2001.

> It's a balance.

It's not. Nobody's punished, no consequences for errors, not even a hint of admission - replaced by blame the victim in the worst crimes imaginary - before looking at the evidence and without even consulting a dictionary to see what the words mean.