Today, there is a vast sea of data about our social interactions and geographical locations. With this new technology, new questions arise about what we can reasonably expect to be private information and, in the context of a criminal prosecution what constitutes a search and seizure. This week, the U.S. Supreme Court ruled on the use of a GPS tracking device by police to remotely track the whereabouts of a suspect's vehicle.

The Court determined that attaching a GPS tracking device to a suspect's vehicle for the purpose of collecting information constituted a search under the Fourth Amendment. Because the police acted outside of the scope of a warrant in their use of the device, the information gathered could not be used as evidence. Based on this reasoning the Court upheld the reversal of a criminal conviction.

If you read this blog regularly or even just watch the occasional police drama, you have likely heard about the "reasonable expectation of privacy" this concept expands our freedom from unreasonable searches beyond just the physical location of our homes or bodies to anyplace in which we have a reasonable expectation of privacy.

Curiously, the majority opinion of the Court did not base its ruling on this penumbral, but well established understanding. Instead the majority opinion said that the act of placing the tracking device on the suspects' car was tantamount to a trespass. It was this trespass onto the property that majority found violated the constitutional protection from unreasonable search and seizure.

It is encouraging that the court found that tracking someone's whereabouts for an extended period of time at least qualifies as a search requiring a warrant. But as technology moves forward quickly, this trespass formulation may not be as broadly applicable as if the court had based their opinion on the reasonable expectation of privacy.

Source: Reuters News, "Supreme Court rules police need warrant for GPS tracking," James Vicini, Jan. 23, 2012