Only the expensive ones. The cheap ones will be used as throw down weapons to frame innocent civilians.
There was an episode on the excellent "Blue Knight" TV series where beat cop "Bumper Morgan" tells of a popular officer who shot an unarmed crook.
To prevent his crucifixion, his buddies on the scene placed a throwaway under the perp's body. When the coroner rolled him over, seven guns were discovered.
Since these episodes were written by a real cop, I have no reason to believe that it didn't happen.