The U.S. Third Circuit Court of Appeals recently held in United States v. Stanley  that law enforcement may utilize Wi-Fi searching technology without violating a defendant’s reasonable expectation of privacy.

In a recent opinion, the Third Circuit considered whether the Pennsylvania State Police violated a defendant’s Fourth Amendment protections when it employed a device called a “MoochHunter” to trace a defendant’s hijacked wireless signal.  After being found in possession of over 140 images and videos depicting child pornography, defendant William Stanley appealed the district court’s order denying his motion to suppress.

In November 2010, the State Police computer crime unit came upon Stanley’s computer IP address from Gnutella, a peer-to-peer network which allows other users to share files without using a central system.  While on the network, the State Police observed a specific IP address exchanging child pornography.

After searching through public records, authorities learned that the targeted IP address was subscribed to Comcast Cable.  Following a court order, Comcast disclosed the subscriber’s name and Pittsburgh address, but, when the search warrant of the home was executed, authorities    learned that the targeted computer was “mooching” off the Comcast user’s unprotected Internet connection.

With consent from the homeowners, the State police connected their laptop to the homeowner’s router.  Weeks later, when the moocher shared child pornography, authorities were able to obtain the moocher’s media access control address and private IP address.  These addresses were entered into the MoochHunter software, and, along with a laptop and a directional antenna, authorities were able to isolate and track Stanley’s location.  With a new search warrant, authorities seized 144 images and videos of child pornography from Stanley’s computer.

The Third Circuit noted that while Stanley may have a reasonable expectation of privacy in his Internet address, it was not legitimate.

Distinguishing his case from Kyllo v. United States, 537 U.S. 27 (2001), the Third Circuit noted that Stanley’s activities were not confined to his home.  Stanley’s actions were deliberately public in that (1) he shared child pornography with other Gnutella users and (2) he did so through another’s Internet connection: “In effect, Stanley opened his window and extended an invisible, virtual arm across the street to the Neighbor’s router so that he could exploit his Internet connection. In doing so, Stanley deliberately ventured beyond the privacy protections of the home, and thus, beyond the safe harbor provided by Kyllo.”

Second, the court analogized the MoochHunter to drug sniffing dogs.  A dog’s nose may detect odors beyond the human senses, but it is not a search within Fourth Amendment in that the dog’s nose does not expose the physical contraband.  The MoochHunter, in comparison, only detects the signal, not the contraband.

But, while Stanley lacked a reasonable expectation of privacy “in the path of his unauthorized signal,” he did not assume the risk that his signal would be revealed.  Generally, a defendant will lack a reasonable expectation of privacy in information voluntarily turned over to third parties. See Smith v. Maryland, 442 U.S. 735 (1979).

Wireless signals are “composed of radio waves that [are] associated with a plethora of information.”  So, while the Internet requires all users to transmit their signal to a third party, the government does not have unfettered access to obtain wireless signals without proper authorization.  Because Stanley exposed his activities to the public domain and did so in an unlawful manner, he lacked a reasonable expectation of privacy.