Hey @Eric H. Steve Babiak gives great advice in this situation. Having written screening criteria is the key to not only keeping complaint, but to making quicker/easier decisions in the future.
For most landlords, the nature of the crime, time since offense, and offenses since then are big factors. In your case specifically, your applicant should warrant a consideration seeing that it's an older offense, and there's been nothing since.
It's understandable to be skeptical of this applicant since he didn't mention anything about the criminal records. However, I can tell you from plenty of experience working directly with applicants that have criminal records, they absolutely find it in their best interest to not mention anything if they think it's sealed or aged off, especially if it's an old record and have no offenses since. I don't see it as malicious intent, just not worth a conversation if there doesn't have to be. They've moved on and enough time has passed the record isn't even on their radar. Unfortunately for a lot of people, they're not aware of their record status and situations like this are a total shock to them. So I wouldn't penalize the applicant too much in this particular situation.
According to the new Fair Housing Guidelines (2016) it's no longer acceptable for landlords to use "blanket polices" when dealing with criminal records. So long gone are the days of "denied due to felony record". Now you have to specify exactly what's acceptable and not acceptable - hence the written screening criteria and exactly what Steve Babiak mentions.