A Windsor family is preparing for an appeal after failing to win dismissal of a speeding ticket with data from a global positioning device in a teenage driver's car.

Sonoma County Superior Court Commissioner Carla Bonilla ruled that Shaun Malone, 17, was guilty of speeding.

The case represents the first time anyone has contested a speeding ticket in Sonoma County using data from such a tracking device.

"We were disappointed," said Roger Rude, the teen's stepfather and a retired Sonoma County sheriff's lieutenant. "We thought we'd be able to raise reasonable doubt. That did not happen."

The ticket was given by a Petaluma police officer. The judge's decision, issued in a written ruling last week, supported the officer's findings.

"That's always been our belief," said Petaluma Police Capt. Dave Sears. "Even though GPS is a valuable tool, it's not being used accurately in our interpretation . . . to sustain a not guilty verdict against the speed. We've consulted with a GPS expert, too."

Global positioning systems pinpoint location and speed using lightning-fast calculations and satellites.

Malone, a junior at Windsor High School, got the ticket on July 4. He was stopped that morning by an officer using radar along Lakeville Highway.

The officer clocked him at 62 mph in a 45 mph zone.

The family contends the car's GPS system shows Malone was driving 45 mph at virtually the same time and at the same place where the officer determined he was driving 62 mph.

The family submitted written information on how the GPS system works, the data from the car and Malone's history, Rude said.

The judge also had information from the Petaluma Police Department about the officer's actions and findings.

Bonilla wasn't available Tuesday for comment.

Malone's mom, Karen Kahn, and Rude had the tracking system put into his 2000 Toyota Celica GTS. The information from the system is downloaded into their computer so they can track his position and his speed, if they choose to.

Rude said it helps the teen learn to drive like there is an officer behind him at all times. If he speeds, Rude takes his son's car keys for a while.

Malone, who has never liked the system, was promised that if he got a ticket and the GPS indicated a discrepancy, his parents would help him fight it.

"I'm honoring a promise I made to him," Rude said.

On Monday, Rude will go to traffic court and file paperwork to start the appeal process.

Rude said more information from the police department on the ticket and the circumstances on the roadway will help him plan his appeal.

An issue, both sides agree, includes where the radar gun clocked him and where the GPS tracker marked him at 45 mph.

The further apart, the less the GPS information is relevant, they said.

"The judge may determine both could be right but they're too far apart," Rude said.

"It really does depend on where the radar reading was taken. If it's within 100 feet or closer, I think they have a very strong case," said Rick Fry, chief information officer for Rocky Mountain Tracking Inc., the Colorado-based company the couple bought the system from. Fry said he will testify in court for the teen if necessary as a GPS expert.

Another issue is the timing of the tracking. Malone's tracking system records his speed every 30 seconds. If the system took more frequent readings, that "would give a more accurate description of what the kid's speed was," Sears said.

Kahn and Rude have become serious advocates for teens using the tracking system. It's bigger than this ticket; it's about saving teens' lives, Rude said.

"Mine and Karen's big motivation is getting the word out to parents there is technology available to them to help monitor their children's driving behaviors and train them into being good drivers," he said.

You can reach Staff Writer Randi Rossmann at 521-5412 or randi.rossmann@pressdemocrat.com.