You think the FBI ever ask anybody is he a rapist?
The fact that you would ask this question demonstrates your ignorance in regards to the FBI, The DOJ, the investigations they conduct for different appointments and security clearances, and how in depth the investigations are.
Yes, in fact I do KNOW that the FBI and the DOJ ask not only YOU but almost every family member, close business partner/associate, and CLOSE military friends / team members extremely detailed questions regarding your finances, personal activities, lifestyle, any legal concerns, etc....
For some background checks and investigations I the past I had to list everywhere I lived, every close friend, every girl I 'seriously dated', every team member I had, and had to answer pages of questions about run-ins with the law, accusations as well not just convictions...all because what I was involved in. I had people I had not seen in 5-6 years call me up and tell me guys in suits and sunglasses paid them a visit asking questions.
So, again, your questions reveals a lack of knowledge / understanding.
This is not a personal attack on you - this is a statement of fact regarding my level of experience in this matter versus, it seems, yours.