Just tell him that you are denying him based on his criminal record that you just became aware of. 

Existing situations are less likely to be reported because it has been that way for a long time.Jail is pretty extreme for a consequence, but if someone gets harmed, you could be held responsible for criminal negligence.

There's no point in running a credit/criminal on someone when you don't even have their ID card to prove they are the person on the application.By the way, at least 10% of all my applicants pay the fee (which is non-refundable) but then never submit the documentation.

They allow you to send your applicants a customized application, from where you can have them screened for their credit, criminal and eviction history.

Aside from the credit, criminal, and eviction reports, the basic info you should ask for would be employment history, rental history, 2-3 references, and 2 emergency contacts to keep on file.

Most landlords - smart ones - run both, plus a criminal check. 

@Noah Willard Have you actually ran the candidates credit, criminal, income, and eviction background to verify what they are claiming?

Like a sex offender or violent criminal?

If they keep asking, we just block them.In my market, if someone is even remotely qualified (income, no evictions, no criminal background) they usually get the apartment.

I tell people over the phone that I don't charge an application fee, but that I do prescreen (evictions, criminal background, income, number of occupants, smoking, pets) over the phone before I will show it.