Law Enforcement Officials carry whatever they personally choose to and are comfortable with. There isn't a mandate that says they have to carry a certain caliber or a certain gun type or a certain brand of ammo. Of course there are recommendations for them, but nothing that is mandatory. As far as types of ammo supplied to them by their department, that will vary from department to department.
I carry 9mm Winchester jacketed hollow points. I love this ammo. It is inexpensive and it has never once misfired or caused any sort of problem for me.
If those do not stop a man dead in his tracks, I don't have anything on me that will.