I AM NOT A LAWYER nor have I slept in a Motel 6 recently, but I believe in California, someone convicted of a sex-related crime becomes a "registered sex offender" for life. They can't live near schools and there are other restrictions. During employee-onboarding, HR must have discovered that this guy has a criminal record. If not, you should discuss this with your manager and HR. If they're a registered sex offender, then the company should follow the guidelines for employing such people.