While relatively rare, the danger of violence in U.S. workplaces is nonetheless chillingly real: Roughly 800 workplace homicides occur each year, according to the U.S. Occupational Safety and Health Administration (OSHA).

Along with that danger, your company could be held liable for an employee’s threats or violent actions.

“By OSHA standards, the company is responsible for providing a safe work environment,” says Don Maida, a senior project consultant for TBR Associates, a consulting firm. “It can get hairy in today’s litigious-prone society; you need to close loopholes,” he says.

First of all, your company ...