Ed Nowicki, who is a POLICE magazine Advisory Board member and the founding executive director of the International Law Enforcement Educators and Trainers Association (ILEETA), believes that one of the biggest problems with the concept of backup guns is that police administrators have a tendency to confuse backup guns with smaller, often less reliable "hideaway guns."

Strictly speaking, a backup gun is a smaller, concealable weapon that can take over the function of a primary duty gun if the larger pistol malfunctions, is lost in action, or is taken away from the officer carrying it. Backup guns are often restricted in caliber by the agencies that permit them. For example, one agency contacted for this article specifies that officers who choose to carry backup weapons must carry a .380, .38 Special, 9mm, .40, or .45.

Hideaway guns are an entirely different animal. Much smaller than backup guns, these pocket pistols are usually .32, .25, or .22 caliber weapons that are only effective at extremely close range. Called "Onion Field insurance" by some old-timers in a reference to an infamous mid-1960s abduction and murder of an LAPD officer, hideaway guns are banned even by many agencies that permit backup guns.

Even proponents of backup guns are dismissive of hideaways as effective weapons. "You need a weapon that works and that's readily available when you need it," says Nowicki, arguing that police should carry second handguns of sufficient caliber to stop a threat.

And reliable compact police calibers are just as effective or more effective as "Onion Field" insurance. "Most bad guys aren't going to think that you have a second gun anyway," says Sgt. Dave Douglas of the San Diego Police Department.

But Douglas, who now serves as his agency's rangemaster, stresses that even a police caliber backup gun should never be mistaken for a duty pistol. "The whole idea of a second gun is concealability," says Douglas. "The concealability gives you the advantage of surprise, but because these guns are much, much smaller than duty weapons, they really are last ditch guns."