In the good old days many PD's and folks in the know switched ammo for the winter season and fired up old duty ammo from the summer. Let me say first though there is not magic bullet that works all the time regardless of bullet weight, type, velocity and so on.

This mainly occured in places where winter meant winter with leather and down filled jackets and layers of clothing were commonplace. Yes the HP cavity would fill and it would effect expansion but it would also effect penetration.
Many tests conducted today with ballistics gel that is covered with varying layers of denim to simulate layers of clothing and in some cases it does greatly effect both the expansion and penetration characteristics of the round. I believe the standard you want is 12-14 inches, but remember that is from all angles. You shoot someone from the side and it has to go through the upper arm, two layer of jacket and shirt, back into the body through two more layers of jacket and shirt then you still want it to meet the penetration standards it's not going to happen guys.

Many officers and civilians used to and still do even go to the point of rotating ammo in their mags, or cylinders, with different types of ammo. HP in the chamber followed by two more followed by ball and so on. Does it work? Who knows. In most of my jobs I am restricted to ball ammo in both rifles and handguns and it works just fine. As stated by others just keep shooting until the person stops doing whatever it is they were doing that caused you to shoot them in the first place.