The usual police "gunfight" is at 21 feet or less (snipers are a special case). Even then, JiK is correct: with the adrenaline flowing and the juices pumped up, even the best-trained shooter can and does miss. Fortunately for the good guys, they miss less often than the bad.

However, when you factor in the general condition of the baddies arms and ammo, lack of practice, lack of training (usually), the care taken of the arms and ammo, you get a huge advantage to the good guys.

A cop,for instance, wearing body armor, can be shot several times by someone using, say, a JA380 (a cheap handgun in .380 or 9mm short or Kurz caliber). Since this weapon only reliably chambers (loads) full metal jacket bullets, any baddie trying more than one shot is liable to get a jammed gun, allowing the cop (bruised by the first shot but in no way really harmed) to use a less lethal means (Taser, baton, etc.) to subdue his prisoner if he wishes.

Of course, it's best not to draw on anyone in the first place. You can avoid a lot of trouble by following that rule.