A Wisconsin court has given approval for police to monitor a suspect through the use of a GPS. The state’s Supreme Court decision involved the case of a man who was booked for stalking his ex-girlfriend, based on data from a GPS, which was installed on his car without his knowedge. The police used the information garnered from the device to prove his location in relation to a stalking case.

The suspect’s defence was that using a GPS to track his movements was illegal as it violated the US Fourth Amendment of unreasonable searches. The court argued that the use of the device was valid as it could be considered a search warrant.

The court said that based on the information provided, “the court finds that there is probable cause to believe that the installation of a tracking device in the below listed vehicle is relevant to an on-going criminal investigation and that the vehicle is being used in the commission of a crime …”.

A number of the judges involved used the case to encourage the state to address the issue of GPS devices and clarify their legal use.

“I believe that the Wisconsin legislature should consider expressly requiring court authorisation of the installation and monitoring of such tracking devices and should consider legislatively setting appropriate parameters and standards for their use,” Judge Ziegler wrote.

She added: “It remains my position that installing and monitoring a GPS tracking device on a vehicle in a public area does not constitute a search or seizure within the meaning of the Fourth Amendment”.