Gun grabbers even want to disarm off-duty cops, for their own safety. In voicing their concern, proponents cite anecdotal scenarios like the death of Sgt. Cornel Young in 2000. Young, an off duty cop trying to break up a bar fight, was shot by police who mistook him for a bad guy. Earlier this year a plainclothes officer was shot and killed by a fellow officer while investigating underage drinking outside the Citrus Bowl. The officer got into a scuffle with tailgaters and fired a shot into the air. An Orlando officer shot him.

In 2001, two uniformed officers shot and killed an undercover detective when he pointed his gun at a suspected car thief in Oakland, Calif.

In 1994, an off-duty police officer in New York City shot and seriously wounded an undercover transit officer who was chasing armed suspects through a subway station. The transit officer survived.

The International Association of Chiefs of Police has called "always on duty" policies a costly tradition. The group, which has more than 20,000 members, recommends that off-duty officers who witness a crime call for assistance rather than pull a weapon.

According to the FBI, 43 police officers have been killed since 1987 by friendly fire. Some were caught in crossfire, or killed by firearms mishaps. A handful, like Young, were mistaken for criminals and shot by fellow officers.