General Aviation airplanes require an annual inspection (from an IA A&P mechanic -- that's airframe & powerplant with inspection authorization). My understanding is that the plane was out of annual (ie, bought as parts) and he fixed it up enough to fly. There are strict limits on what repairs you can do yourself without involving a licensed A&P mechanic. FAA actually does ramp checks on occasion to verify that your bug smasher has up to date registration and annual inspection. Regardless of how the flight ended, the flight shouldn't have happened in the first place and his PPL could be revoked for that alone.