Six months ago, we wrote about the legal confusion about whether police officers could track a person's movements by placing a GPS transponder on that person's car without a warrant to do so.

If private citizens place those same transponders--especially if they're former boyfriends or estranged husbands, against whom orders of protection have been issued--it's a moot issue.

That's called "GPS stalking," and it's almost always illegal. Just ask five-time All-Star outfielder Albert Belle, who went to jail for satellite-stalking a former girlfriend.

D.C. Appeals Court: Get a warrant

Now the U.S. Court of Appeals for the District of Columbia circuit has voted to uphold a lower court ruling that police must obtain a warrant to track a suspect using a GPS device on his car.

In a sharply divided 5-4 ruling, the appeals court declined a request by the U.S. Department of Justice to overturn the ruling of a three-judge panel saying that police had violated the "reasonable expectation of privacy" of a man on whose car they placed a transponder, who was subsequently convicted of operating a drug ring.

A "reasonable person does not expect anyone to monitor and retain a record of every time he drives his car, including his origin, route, destination and each place he stops and how long he stays there," wrote U.S. Circuit Judge Douglas Ginsburg in the majority option.

The Appeals Court ruling may be further appealed, with the possibility that the Supreme Court will have to weigh in on the issue. If it does so, it will have to decide which of a group of conflicting decisions across various U.S. regions are constitutional and comply with existing law and precedent.

Wisconsin: Cops can track anyone

This spring, for instance, a court in Wisconsin ruled that police may mount GPS transponders on cars, and track citizens' movements, without violating their state constitutional rights. Even more, the police may do so for any person at all, even if those drivers are not suspects in any criminal case.

The Wisconsin court reasoned that a person's location constitutes "public information," since anyone can see a car drive past. Hence, GPS tracking does not constitute either search or seizure, and no search warrant is needed (although in this case, the police had obtained a warrant).

In the unanimous ruling, Judge Paul Lundsten wrote that the information from the GPS transmitter gave the police only "information that could have been obtained through visual surveillance".

New York: It's illegal search

Contradicting that line of reasoning, the New York State Court of Appeals decided that New York State Police officers had "violated a criminal suspect’s rights" under the New York state constitution when they placed a GPS transponder inside the bumper of a van owned by Scott Weaver of Watervliet in December 2005 and left it there for 65 days.

The court ruled that using a GPS tracking device without a warrant was an illegal search, though only within New York state, since there is no U.S. Supreme Court ruling that addresses the issue of whether using GPS for a criminal investigation constitutes a search as described under the Fourth Amendment.

Whether this case or another goes to the Supreme Court, the issue will continue to be sharply divisive, pitting law-enforcement agencies, prosecutors, and the Department of Justice against such civl-liberties groups as the American Civil Liberties Union and the Electronic Frontier Foundation.

[Washington Times]