Approach to Old felonies not disclosed in prescreening?

[Eric H.]

Newer landlord and first time turning a unit.  Tenant said he had no felonies when I screened over the phone. 

I ran him through Rentprep and turns out he has a felony for "DELIVERY/MANUFACTURE MARIJUANA" from 1998 when he was 18 years old.  When I asked him about it he said he thought those records were sealed and that's why he didn't mention it. 

Besides this he's a good candidate but I'm bothered by him not telling me.  I'm more concerned that him didn't tell me then the felony itself.

How do you guys view old felonies like this?  What would you do in this situation