Yesterday the U.S. Supreme Court threw out the conviction of a man sentenced to life imprisonment on the basis that key information used to prosecute him had been illegally obtained. 

A GPS tracking device, which reported its location via the cell phone network, had been placed on the defendant’s car without a warrant. Four weeks of nearly continuous tracking provided the basis of an indictment and subsequent conviction for drug trafficking. In a victory for privacy advocates, the Supreme Court ruled that this tracking violated the American constitution’s Fourth Amendment protections against warrantless searches and seizures of “persons, [and their] houses, papers, and effects.” 

Because the decision did not fall along the usual conservative versus liberal lines, and because there are competing views among the justices on just how the Fourth amendment was violated, this case has provided a great deal of grist for the mills of court watchers (for an excellent dissection of the legal issues, see the SCOTUSblog’s coverage.) 

But a broad swath of technology industries are also paying attention, as the court has taken the opportunity to clearly signal its interest in the Fourth Amendment implications of warrantless electronic surveillance through things such as e-mail records, GPS-enabled smart phones, or in-car assistance technologies. 

In this particular case, the majority decision of the court hinged on the finding that, by attaching a physical tracking device to the defendant’s car in the absence of a valid warrant, law enforcement officials committed an act of trespass. But, even as they restricted their judgement to these narrow grounds, the judges warned that, “It may be that achieving the same [tracking] through electronic  means, without an accompanying trespass, is an unconstitutional invasion of privacy …” 

Thus, while declining to say one way or another, it’s likely that the court will accept for a review a future case speaking to these issues should one arise, which it it almost inevitably will, given today’s fuzzy boundaries between public and private information. For example, just because I disclose my location to my cell phone carrier, is that information really  open for the police to peruse without a warrant,especially as disclosing that information is essential to using the service? And what about, say, nonessential but nonpublic information shared with a social network? 

What’s clear is that the Supreme Court is aware of the often permeable membrane between a communications technology and a surveillance technology. 

Which particular such technology will ultimately fall under the Court’s microscope is impossible to guess, but which ever one does, it’s likely to produce a landmark ruling that will go a long way to defining the societal auspices under which these technologies operate, as they complete their transition from optional extras to essential products and services required by most people.