Even if this passes (which is not happening), I don't see it having any realistic effect on anything.
Judge: Officer, why did you shoot Mr. What'shisname in the chest instead of aiming for the legs?
Cop: I did aim for the legs but he kept moving and I missed and hit his chest.
There would be no real way of telling whether the cop really tried aiming for the extremities. Besides cops usually don't have too much trouble getting out of a unjustified shooting trial with nothing more than a desk assignment for a few weeks. Unless there is just completely overwhelming evidence against them.
I live in NYC and I can tell that if this law were to pass the cops will brew up a s**t-storm so big the entire legislature will drown in it.