They're gonna say he "thought" the guy was a felon, but that goes down the path of pre-crime conviction. If I "thought" I was doing any other crime and it was proven that I hadn't, that case would be dropped in a heartbeat.
Also, why is it illegal (i.e. perjury) for us to lie to congress, our servants or a court of (cough-cough) law, but not so for OUR representatives, servants and government officials to lie to us. All of government's perjury to us should be a higher crime than ordinary people's perjury to those who answer to us.
And even more importantly, since our fine is held as a personal liability and their's is passed on to the department, it represents a SYSTEMIC SHIFT IN THE HIERARCHY OF THE MASTER-SLAVE RELATIONSHIP.