Yeah, it sounds like the cop wrote the ticket to cover his arse for the stop and the judge knew exactly why he stopped your son and wasn't going to make your son pay a fine just so the cop could cover his arse.

I have had similar situations myself. Many times at night during those hours I get stopped for petty and even invented reasons but once they find out I'm not drunk they usually let me go with a 'warning' or a 'have a nice night.'

One time really POed me though, and it was similar to your son's situation. I had stopped late at a club because a DJ friend I knew was spinning there that night. I used to do some DJing years ago with a local DJ company in order to pick up extra cash and made some lasting friends from it, including the owner. In fact, some are clients of mine today for legal purposes.

I left the bar at last call. I had nothing but Diet Coke all night. The parking lot was across the street. I walked across to my car, hopped in, pulled out, and made a left heading to the traffic light at an intersection a few hundred yards down the road. I noticed a cop idling in the filling station across the street. He was watching everyone as they left the bar.

I turned left when the light turned green. I then turned right at the next block to head out of town towards home. By the time I was about four blocks down I noticed a cop with his lights on pulling me over. It was the same cop from the filling station lot. He told me I made an illegal left turn on a red light and that I was swerving back and forth over the double yellow line in the middle of the road. I was livid. He then asked me if I had anything to drink. I flatly and firmly denied it.

Whilst this was going on, another backup cop car arrived. The cop then asked me to get out of my vehicle so he could perform a sobriety test. I told him flatly and firmly that I never swerved or turned on a red light, that he saw I turned on a green light, and wouldn't be able to see me swerve because I hadn't and, even if I had, that he couldn't see me do that anyway given his position in the lot versus the road because buildings would block his view and I was around the next corner by the time he must have gotten out. I also insisted that I hadn't drank a drop of alcohol all evening and it appeared to me that he was merely just trying to stop my car because he saw me just exit the bar, especially since he had already called a backup police car.

The cop got suspicious that I seemed to know the law on car stops and police routines, especially with DUI. He asked me what I did for a living, and I told him I was a criminal defence attorney. He got nervous then and told me he believed me that I hadn't drank anything and got much more polite and backed off immediately. But, he then wrote me a turn signal violation to cover his arse, especially since he has radioed in a backup car. I pled not guilty the next morning before he could even file his ticket. That way, I made sure the cop knew that I did so when he came in to file his tickets to get the message this was not a ticket he wanted to litigate. When the court case date arrived, he decided to not show up and I was found not guilty.

Had I been intoxicated, though, I would have been arrested, and I'm sure, like most defendants, would have lost any credibility dispute between my version of the events and his if I tried to suppress the evidence due to an illegal car stop.