An unfortunate policy, IMHO. If the shot is fired in such a way as to avoid endangering anyone, and if it causes a would-be criminal to realize that he has an urgent appointment elsewhere, firing a warning shot may be better for all concerned than waiting until one would have no choice but to fire center-of-mass. Perhaps some might argue that it would be better for society if the criminal received a center-of-mass shot rather than living to "crime" another day, but I would suggest that forcing apparent criminals to make their intentions clear "early" is good. Among other things, a policy that the only "warning" is a center of mass shot risks the possibility that one might be forced into a choice between shooting someone who is only 99% likely to be a dangerous criminal, or surrendering any tactical advantage one might have over such a person. Firing a warning shot while one still had time to do so would avoid that danger.
I'm not saying that I think warning shots should be required, or even particularly encouraged. On the other hand, there are situations where they really would seem like the safest course of action (though in some legal climates perhaps one was simply "target shooting").
That’s a lot if’s for a jury/prosecutor who could well be fire arm ignorant to decide. I would never miss on purpose, some one chooses to whateve.... admitting it is the crime ;)