Falsification of legal doents- how to expunge?

A few years ago I lied on a police report to try and help someone get out of trouble, the officer knew all along i was lying and so I was charges with falsification of legal doents. Now it's almost 3 years past and the charge is making it hard for me to find a job because many places tell me they do not hire people with 'a history of dishonest behavior' so I'm wondering if there's any way to have this expunged.