Citizens account for a third of the justifiable homicides according to the FBI
http://www.fbi.gov/ucr/cius_04/documents/CIUS2004.pdf
FBI 2004 Uniform Crime Reports
Justifiable Homicide
Page 24
Law Enforcement 2000-2004 The killing of a felon by a law enforcement officer in the line of duty.
Year
2000 309
2001 378
2002 341
2003 373
2004 437
Private Citizen 2000-2004 The killing of a felon, during the commission of a felony, by a private citizen.
Year
2000 164
2001 222
2002 233
2003 247
2004 229