Prosecutors in the Scott Peterson (search) double homicide trial may introduce evidence gleaned from electronic tracking devices secretly planted on his vehicles before his arrest last spring, a judge ruled Tuesday.

Judge Alfred A. Delucchi said that Global Positioning System (searchtechnology, which has never been tested in California's criminal courts, is "generally accepted and fundamentally valid."

The ruling means a jury in the murder case will hear evidence on Peterson's comings and goings in the weeks following the disappearance of his pregnant wife on Christmas Eve of 2002. Defense lawyers had asked the court to toss the evidence from the tracking devices, arguing glitches made the data unreliable.

But Delucchi decided prosecutors had established both GPS' reliability and demonstrated that the it was used correctly — the two legal tests for the nascent technology.

Hugh Roddis, president of Orion Technologies Ltd. (search), which sold Modesto police the covert devices used in the Peterson case, testified early Tuesday.

"I think this unit is one of the better ones on the market," he said, adding he wasn't sure whether any Modesto police officers had been trained to use the unit but bristling at Geragos' suggestion that police bought cheap devices.

Delucchi asked Roddis whether he believed the device was used properly in this case.

"I would believe so, yes," Roddis replied.

Geragos seized on tracking errors in several of the devices Modesto police used, including one that he said didn't work for nearly three weeks.

Roddis blamed the errors on inaccurate maps, a faulty wireless antenna and a bad microprocessor connection.

Testimony about police tracking of Peterson's whereabouts began last week, when Peterson's attorney Mark Geragos tried to poke holes in the accuracy of the GPS devices, particularly when placed secretly on vehicles.

The military developed the satellite-based radio navigation system, which can pinpoint a user's location within feet at any time. The technology is now in common use from major industries to weekend wilderness warriors.

Police installed the devices in vehicles Peterson owned, borrowed and rented after Laci Peterson disappeared on Christmas Eve 2002, saying they trailed him to San Francisco Bay at least once in January.

If he's convicted of the murders of his wife and their unborn son, Peterson could face the death penalty.

Bound by gag orders, neither side has discussed what evidence would be lost or gained from information the tracking devices gathered.

The Associated Press contributed to this report.