If you carry a weapon-mounted light, a second handheld light on your duty belt will allow you to scan without taking direct intense light off the subject. These high intensity lights also get hot and tend to blow bulbs more easily when they are hot. If one light goes out it could be a disaster without a back up immediately at hand. A Surefire X200B model (LED will not blow) on the gun and a G2Z or M3 in a quick access holster on the belt is an unbeatable combination.