In a unanimous ruling today, the Supreme Court ruled the government placing a GPS on an individuals vehicle constitutes a search and as such requires a warrant under the 4th Amendment.
The case was United States v. Antoine Jones, Washington Post reports:
The Supreme Court ruled unanimously Monday that police must get a search warrant before using GPS technology to track criminal suspects.
A GPS device installed by police on Washington, D.C., nightclub owner Antoine Jones’ Jeep helped them link him to a suburban house used to stash money and drugs. He was sentenced to life in prison before the appeals court overturned the conviction.
This is a great victory for civil libertarians, though there are some reasons to still be cautious and to push for more protections. For instance, while the Justices agreed this specific instance constituted a search, there were differing reasons for them eventually coming to the same conclusions.
Those of you who are interested in reading the full opinion can find it here.
For a summary view, Cato's Jim Harper explains it well:
Without rejecting Katz and "reasonable expectations", the Jones majority returned to property rights as a basis for Fourth Amendment protection. “The Government physically occupied private property for the purpose of obtaining information” when it attached a GPS device to a private vehicle and used it to gather information. This was a search that the government could not conduct without a valid warrant.
The property rationale for deciding the case had the support of five justices, led by Justice Scalia. The other four justices would have used “reasonable expectations” to decide the same way, so they concurred in the judgement but not the decision. They found many flaws in the use of property and “18th-century tort law” to decide the case.
Justice Sotomayor was explicit in supporting both rationales for protecting privacy. With Justice Scalia, she argued, “When the Government physically invades personal property to gather information, a search occurs.” This language—more clear, and using the legal term of art “personal property,” which Justica Scalia did not—would seem to encompass objects like cell phones, the crucial tool we use today to collect, maintain, and transport our digital effects. Justice Sotomayor emphasized in her separate concurrence that the majority did not reject Katz and “reasonable expectations” in using property as the grounds for this decision.
Sotomayor, Harper points out, was the only one who mentioned the unresolved issue of the third-party doctrine.
The third-party doctrine cuts against our Fourth Amendment interests in information we share with ISPs, email service providers, financial services providers, and so on. Reconsidering it is very necessary.
Justice Alito, writing the opinion based on an individuals' "reasonable expectation" of privacy, notes that this case also does not resolve the issue of whether warrants are required for "remote tracking" -- i.e. tracking an individual's whereabouts using their own cell phones' GPS.