On Tuesday, the that state police must obtain a warrant before installing a GPS device on an individual's vehicle for tracking purposes.

The decision stems from a case in which Latham police, as part of their investigation of a string of burglaries in 2005, secretly installed a GPS tracking device on the vehicle of an individual named Scott Weaver and tracked his movement for 65 days. Weaver was convicted for robbing one store based at least partly on the GPS tracking, which showed he had traversed that store location at a very slow speed on the evening of the robbery.

Weaver appealed the decision, saying that the GPS tracking had been done without a warrant and constituted a violation of his right against unreasonable search and seizure. In upholding that appeal and granting Weaver a new trial, Chief Judge Jonathan Lippman held that the sort of detailed surveillance enabled by GPS devices mandated judicial oversight. Without it, "the use of these powerful devices presents a significant and, to our minds, unacceptable risk of abuse," Chief Judge Lippman wrote.

On the surface, that decision seemed to be at odds with one made by the in the case of a man who was convicted on stalking charges. The court ruled that the evidence gathered against him using a secretly installed GPS tracking device on his car did not constitute a violation of his Fourth Amendment rights against unreasonable search. In coming to that decision the court avoided directly addressing the issue of whether a warrant is explicitly needed to conduct such GPS tracking in the first place.

But the Wisconsin court's opinion reflected many of the same concerns against the unsupervised used of GPS devices that were expressed by the New York court. Judge Paul Lundsten said the court was "more than a little troubled" by the lack of federal and state laws limiting the government's use of GPS tracking devices. He urged the state's legislature to explore laws imposing limitations on the use of GPS by both government and private actors.