Before Scott Peterson was charged with the murders of his wife Laci and their unborn son, police put a tail on him -- a GPS device to track his whereabouts.

During his surveillance, Peterson allegedly traveled twice to where the victims' bodies were later found. The information gathered from the GPS tracking may be presented to a jury as part of a largely circumstantial case that the prosecution hopes will convict Peterson.

A judge will decide whether that information is admissible, and whether the technology is "junk science" and as unreliable as the defense is arguing. The case is one of the first in California -- and the country -- to challenge the admissibility of tracking technology in court.

The technique has been used before. In Washington state, police placed a device on the car of a suspect accused of killing his 9-year-old daughter. Police acted under the premise that suspects often return to the crime scene. Indeed, the man eventually, unknowingly, led police to the victim's grave, and was convicted of the murder.

The defense sought to have the case thrown out -- claiming the premise on which police were granted the warrant to use the GPS device was flimsy. The prosecution argued two things: One, police didn't need a warrant in the first place, and two, they could have obtained a conviction even without the evidence gained with the GPS technology.

The case went to Washington's Supreme Court, which ruled that police did need a warrant to attach such a device and that the warrant was correctly issued in the case. The case is considered precedent-setting in extending rights to suspects. In previous cases involving conventional means of surveillance, such as with a vehicle or binoculars, courts have ruled there were no rights of privacy.

The Washington case differentiates between those methods and the placing of a GPS device.

In the unanimous decision, Justice Barbara Madsen wrote: Use of GPS tracking devices is a particularly intrusive method of surveillance, making it possible to acquire an enormous amount of personal information about the citizen under circumstances where the individual is unaware that every single vehicle trip taken and the duration of every single stop may be recorded by government.

Madsen said the prospect of citizens being tracked to places -- such as a baseball game, a strip club, the wrong side of town or the grocery store -- weighed heavily on her decision.


Emerging Tools
The consensus is that GPS technology and other location technologies will become more of a tool for law enforcement as government catches up to the technological curve. As this happens, questions about how and when it is appropriate for law enforcement agencies to use these tools will likely arise.

"I'm a firm believer, and the FBI is proving this as we speak, that governments -- federal, state and local -- are behind the eight ball in technology," said P.J. Doyle, president of CJIS Group, a criminal justice research organization. "As the new technologies emerge, government is behind. Law enforcement is even further behind to the point that by the time they start using the technology, it's not considered emerging anymore."

Nevertheless, once law enforcement agencies begin using the technologies, legalities of use will have to be addressed, Doyle said.

"Any emerging technology requires statutes, laws and ways you can get the data," he said. "Laws are actually made as they're needed and interpreted as they're used."

Doyle expects that process to play out with satellite technology, which he predicted will be a "major mover and shaker with satellite phones and other equipment," over the next few years.

The consensus is that GPS is one of those emerging tools for