Is it lawful for the police to hide a Global Positioning System (GPS) tracking device on an individual's car without a valid warrant and monitor the person's movements for the following month?

The United States Supreme Court ruled unanimously last week that there is a constitutional requirement for the police to obtain a judge's warrant to track a suspect by attaching a GPS device to the target's car. Unlike closed-circuit television video monitoring, the installation of a GPS device requires law enforcement to actually trespass on private property. The majority opinion of the Supreme Court held that this occupation of private property resulted in an overly intrusive search.

A number of the justices, however, were also concerned with the broader impact of GPS technology. Its ability to produce unchecked long-term monitoring clashed with modern notions of reasonable expectations of privacy.

Justice Sonia Sotomayor highlighted the particular dangers that GPS tracking posed to privacy rights. In a concurring opinion she noted that ''GPS monitoring generates a precise, comprehensive record of a person's public movements that reflects a wealth of detail about her familial, political, professional, religious, and sexual associations. ''

The government's unlimited power to assemble data about a person's behaviour by their locations visited is potentially open to abuse. As described by Justice Sotomayor, GPS electronic surveillance permits the police to monitor a suspect's movement's, store the records that are collected and rely upon this information years into the future.

In Canada, the Criminal Code specifically provides for tracking warrants and the installation of tracking devices. A tracking device is defined as including an electronic device that assists in determining the location of a person.

In granting the warrant, the justice must be satisfied that there are grounds to suspect that an offence has been or will be committed and that relevant evidence can be obtained. This includes the whereabouts of any person. The warrant may only be valid for up to a period of sixty days although it may be renewed.

The requirement for a warrant in both Canada and the U.S. for GPS tracking is an example of the law adapting to the rapid advancement of 21st century technologies. New frontiers of state surveillance will undoubtedly pose future legal challenges.