Beware the digital trail you may be leaving

News Global Positioning Systems (GPS) and factory-installed "black box" event data recorders could provide evidence in a court of law.

In their leather upholstered cocoons equipped with soothing high-tech sound systems, drivers have come to regard their car interiors as mobile extensions of the homes that are their private refuges. The courts, however, have tended to disagree. Global Positioning Systems (GPS) and factory-installed "black box" event data recorders effectively keep vehicles under surveillance, providing evidence that can place a suspect at a crime scene or prove liability in an accident.

Although privacy rights experts warn that the devices augment an already intrusive network of security cameras, radars and instantly available databases, prosecutors hail the technologies as powerful investigative and forensic tools. GPS records introduced at a trial put a man at the scene of arson fires, leading to his conviction in October for starting a dozen blazes in California, USA in 2006. In murder cases in Illinois, Washington and California, the technology has been credited with helping establish guilt.

The evidence is sometimes the product of unwitting surveillance. GPS units keep positioning tracks that, if not erased, create a record of a person's movements. Event data recorders are standard equipment in most new cars. They record speed, braking and other driving behaviours. David A. Schumann, a lawyer from the state of Wisconsin, who did some of the earliest legal analysis of GPS potential, points out its usefulness in tracking suspects, locating victims and monitoring convicts.

"There are cases where people have been hung by their own GPS," Schumann said. He recalled the trial of a man compelled to plead no contest to criminal charges after using a GPS to stalk a former girlfriend. In the privacy debate, courts so far have come down on the side of taking advantage of the crime-solving value of the technology. The technology is, however, still in its infancy and its development is limited by funding priorities that vary, said Scott Thorpe, head of the California District Attorneys Association.

"But are prosecutors taking advantage of this when available?" he said. "Absolutely." Law enforcement is benefiting from the technologies as an investigative tool, he said. "GPS transmitters are so cheap and available that they are already in use and provide advantages beyond anything we ever had, to include the exact route a vehicle travels, where it parks, for how long and many other things," said Sid Heal, a recently retired commander responsible for technology development with the LA County Sheriff Department.

The black boxes installed in new cars have the potential to provide insurance companies with accident information useful in defending or prosecuting claims, and many insurance policies contain fine print obliging drivers to turn over the event data recorders in liability investigations. "That's my problem with this, from the privacy perspective," John Soma, a University of Denver law professor and executive director of its Privacy Foundation.

"The car comes equipped with it. They can't disable it. There hasn't been any meaningful legislative discussion of this or any meaningful notice that this is now in your car." Soma worries that the law enforcement view is that only people with something to hide would have objections to being under surveillance. "I think that assumption is wrong," he said, calling for public discourse on what limits are appropriate to a technology that can track and record a drivers every movement.