He maybe have been working in an unlicensed or non-company approval holder position which would probably be acceptable in the employers eyes. Up to them really if they know his history and maybe they discussed it with CASA. If however it was a Licensed position it should raise a few questions and further investigation....assuming of course he has not completed Licence modules and been issued with a Licence in the meantime. Post the previous events, was he legally banned or "black listed" by CASA somehow from working in the industry or holding a licence?
Not defending him and I don't know any of the names at the start of the thread, but the above has to be factored into any potential scenario.
I wouldn't have thought he would have been able to obtain an ASIC to allow him to work in the industry with his criminal record.