On Sept. 16, military information technology subcontractor Aaron Alexis took a shotgun into the Washington Navy Yard and killed 12 people. Alexis’ employer, The Experts, hired Alexis after conducting an allegedly complete background investigation. While many companies screen their own employees, few conduct due diligence on their contractors’ employee screening processes. Subcontractor employees often have the same work site access and even wear the same company badges as regular employees – though the company’s human resources personnel and managers don’t directly screen or manage subcontractor personnel. Many employers seek out the cheapest, fastest background check firms; these firms may perform cursory screens that provide only the illusion of security. For example, the background checking firm turned up Alexis’ traffic violations but not his more serious gun-related arrests. As in so many workplace violence debriefs, after the tragedy individuals in Alexis’ company reported earlier suspicious conduct that worried them. These concerns were never raised to a level where they could be dealt with. When contracting for services, companies can insist that contractors’ employees undergo thorough background screening and can review their subcontractors’ background screening processes. Employers using a third-party background screener can also screen the screeners.