"Nearly all officers were employed by a sheriff’s office that used criminal record checks (99%), personal interviews (98%), background investigations (98%), and driving record checks (95%) (figure 4). More than 4 in 5 officers were employed by an office that used medical exams (87%), and drug tests (85%). More than two-thirds were employed by one using psychological evaluations (72%) and credit checks (69%). More than half of officers worked in sheriffs' offices using written aptitude tests (58%) and physical agility tests (54%)."


Hickman, Matthew J. and Reaves, Brian A., "Sheriffs' Offices 2003" (Washington, DC: USDOJ, Bureau of Justice Statistics, May. 2006), NCJ 211361, p. 8.