So he goes down to the police station ( or county sheriff office) and the report they run does not show his convictions ?
1. where they part of a plea deal, perhaps where after probation charges dropped as a first offender program perhaps ?
2. Where the charges done though a city court, perhaps ? some city courts do not report minor charges to the national system.
If he is getting his report from some "internet" background check many are not that good.