Cobra Radar Detector Speeding Ticket!

When my husband used to travel three hours to come see me when we first met, he though he would try to save a little time and go a little faster then usual ( maybe 80 instead of 70 mph here in MI 70 is the speed limit ) so he bought himself what he thought was a great radar detector. The Cobra radar detector worked when it wanted to. One time while on his way down to see me, he noticed lights behind him and heard the dreaded sound of a cop car. He couldn't beleive it! The radar detector didn't even light up a little... ten minutes later a speeding ticket. So we thought maybe it was the cop who had some new laser, or maybe the radar detector wasn't set up the right way. So we checked it to make sure and well it would work sometimes and not others. We then decided to no longer count on it and stopped going over the speed limit. So if you want a speeding ticket this is not the radar to buy, I'm assuming the best ones to buy are the ones that are more expensive.