In a big loss for the federal government, the Supreme Court held today that when the government attaches a GPS device to a vehicle to monitor the vehicle’s movement, the government conducts a Fourth Amendment search. Justice Scalia wrote the opinion for the Court in United States v. Jones, No. 10-1259, backed by the Chief Justice, and Justices Kennedy, Thomas, and Sotomayor. You can read the opinion here.

Justice Scalia said:

It is important to be clear about what occurred in this case: The Government physically occupied private proper­ty for the purpose of obtaining information. We have no doubt that such a physical intrusion would have been considered a “search” within the meaning of the Fourth Amendment when it was adopted.

Concurring in the judgment was an unusual line-up of Justices Alito, Ginsburg, Breyer and Kagan. Justice Alito argued that:

This case requires us to apply the Fourth Amendment’s prohibition of unreasonable searches and seizures to a21st-century surveillance technique, the use of a Global Po­sitioning System (GPS) device to monitor a vehicle’s move­ments for an extended period of time. Ironically, the Court has chosen to decide this case based on 18th-century tort law. By attaching a small GPS device to the under­side of the vehicle that respondent drove, the law enforce­ment officers in this case engaged in conduct that might have provided grounds in 1791 for a suit for trespass to chattels. And for this reason, the Court concludes, the installation and use of the GPS device constituted a search. Ante, at 3–4.

This holding, in my judgment, is unwise. It strains the language of the Fourth Amendment; it has little if any support in current Fourth Amendment case law; and it is highly artificial.

I would analyze the question presented in this case by asking whether respondent’s reasonable expectations of privacy were violated by the long-term monitoring of the movements of the vehicle he drove.