It is illegal to ask about arrests or charges. You are allowed to ask about convictions.
Some states have restrictions on using information about convictions.
For example, California does not allow employers to consider employee's convictions for marijuana possession. This is illegal under the Americans with Disabilities Act, which applies if you have 15 or more employees. The essential functions should be listed in a written job description and should include such things as ability to work under stress or other requirements needed for those particular jobs. If the doctor's report says the individual needs reasonable accommodation, you cannot refuse to hire them on that basis unless the accommodation would cause an undue hardship on your company. If you get to that point, it is best to get a lawyer involved before making the decision that it is an undue hardship.