The problem here is that the driver had a GPS tracker placed in his car by his employer in order to control speed limit violations. The tracker indicated that he was going 50 mph, not 84. The court ruled that they could not accept the reading of the tracker without expert testimony from the manufacturer that would testify to the accuracy and method of operation of the device. According to the court:
"Barnes presented no evidence from a person with personal knowledge regarding how the GPS calculates speed, whether there is any type of calibration of the equipment used to detect speed, whether the methods employed by his particular company to detect speed are scientifically reliable, or the accuracy of the GPS' speed detection," the panel said.This would have required that the accused hire an attorney and expert witnesses to attend the trial. To beat a $35 traffic ticket (I wish. In Florida, a speeding violation of 84 in a 65 will cost you $180) you are expected to spend several hundred dollars.
Meanwhile, the government has a bottomless checkbook with which to defend their cash cows. In Sonoma county, CA in 2009, the government of Petaluma spent tens of thousands of dollars to beat the GPS readings. Protecting speeding ticket fines, a $10 billion per year scam, is of utmost importance.