If you ever wonder why you run background tests, or why someone with a violent criminal past is considered an undesirable employee, the "Homicide Victim and Suspect Analysis Report 2008" is a good reference. The report is a clinical study of violent crime centered on the city of Baltimore, MD.
It chronicles over 300 violent deaths in the city and categorizes them by location and type of death: by handgun in the street.
Of the 107 suspects arrested for violent crime, a whopping 94 had criminal records mostly consisting of drugs, guns, and violent crimes. 36 of those were under probation at the time of their crime.
Of 234 victims, 194 had criminal histories.
If you want to keep violence out of the workplace, keep the criminals out!