Shaun Malone was 17 when a Petaluma police officer pulled him over on Lakeville Highway the morning of July 4, 2007, and wrote him a ticket for going 62 mph in a 45-mph zone.

Malone, now 19, was ordered to pay a $190 fine, but his parents appealed the decision, saying data from a GPS system they installed in his car to monitor his driving proved he was not speeding.

What ensued was the longest court battle over a speeding ticket in county history. The case also represented the first time anyone locally has tried to beat a ticket using GPS.

Nationally, such cases remain rare, despite the growing use of such technology in vehicles, primarily for mapping purposes.

In her five-page ruling, Commissioner Carla Bonilla noted the accuracy of the GPS system was not challenged by either side in the dispute, but rather they had different interpretations of the data.

All GPS systems in vehicles calculate speed and location, but the tracking device Malone's parents installed in his Toyota Celica downloaded the information to their computer. The system sent out a data signal every 30 seconds that reported the car's speed, location and direction. If Malone ever hit 70 mph, his parents received an e-mail alert.

Malone was on his way to Infineon Raceway when Officer Steve Johnson said he clocked Malone's car going 62 mph about 400 feet west of South McDowell Boulevard.

The teen's GPS, however, pegged the car at 45 mph in virtually the same location.

At issue was the distance from the stoplight at Freitas Road -- site of the first GPS "ping" that showed Malone stopped -- to the second ping 30 seconds later, when he was going 45 mph.

Bonilla said the distance between those two points was 1,980 feet, and the GPS data confirmed the prosecution's contention that Malone had to have exceeded the speed limit.

"The mathematics confirm this," she wrote.

The defense also attacked the accuracy of radar, saying Johnson's readings could have been affected by everything from reflections off street signs to him erroneously locking on the wrong vehicle.

But Bonilla sided with the officer, stating he received a clear Doppler tone indicating no interference. Given Johnson's experience, including 15 years in the traffic division, and his observations on the morning in question, "the notion that he may have picked up a different vehicle is speculation," Bonilla wrote.

The case also drew interest because of the time and expense that went into what in essence was a fight over the $190 traffic ticket.

Petaluma police said it's a matter of routine to defend such challenges, but in this particular instance, concerns that the case could set a legal precedent that could jeopardize law enforcement's use of radar for speed enforcement factored into their decisions.

That included spending $15,000 on an expert in GPS technology -- including for one court appearance that had to be postponed when Andrew Martinez, the attorney retained by Malone's family, asked for a continuance.

"This case ensures that other law enforcement agencies throughout the state aren't going to have to fight a case like this where GPS is used to cast doubt on radar," said Sgt. Ken Savano, who oversees the traffic division.

Bonilla, however, denied the department's request to be reimbursed $5,000 for the hearing that had to be postponed.

Malone's stepfather, retired Sonoma County Sheriff's Lt. Roger Rude, said Bonilla's ruling does not change his belief that the GPS proved Malone was not speeding that day.

He called the calculations referenced by Bonilla "flawed" and said her ruling weighed heavily in favor of police testimony.

"The impression I came away with, at least in traffic court, is that you are guilty until proven beyond a reasonable doubt," he said.

Rude said Martinez refused payment to handle the case, meaning his family is only out the $190 fine. And that, Rude said, will be paid by Malone's mother, who also believes her son to be innocent.

You can reach Staff Writer Derek J. Moore at 521-5336 or derek.moore@pressdemocrat.com.