[JURIST] A Missouri law [HB 1108 materials] allowing police to track individuals’ cell phones in emergencies was challenged in a federal lawsuit Monday claiming that the state law conflicts with federal law. The complaint [text, PDF], filed on behalf of a Bolivar resident, asserts that the Missouri law should be struck down under the supremacy clause of the US Constitution as it clashes with federal law. The Missouri law requires phone companies to help law enforcement agencies [AP report] in tracing cell phone signals of 911 callers or tracking a phone’s location in emergency situations. The lawsuit seeks a restraining order or injunction prohibiting enforcement of the law.

Government use of modern technology to monitor and locate citizens has created legal uncertainty recently. Earlier this month a panel of judges for the US Court of Appeals for the Sixth Circuit [official website] ruled that police did not violate the Fourteenth Amendment [JURIST report] protection against illegal searches when they tracked a suspect’s cell phone using the phone’s global positioning system (GPS) [JURIST news archive] signal. Also this month, the American Civil Liberties Union announced that their affiliates are sending approximately 375 requests for information in 31 states to reveal how law enforcement uses location data tracking on cell phones [JURIST report], arguing that the warrantless tracking of GPS signals is unconstitutional. In June lawyers for the US Department of Justice defended the warrantless use of GPS devices [JURIST report] on suspects’ vehicles despite a recent Supreme Court ruling declaring GPS tracking to be a “search” under the Fourth Amendment. The Supreme Court concluded that the government’s attachment of a GPS device to a vehicle, and its use of that device to monitor the vehicle’s movements, constitutes a search under the Fourth Amendment. Also in January, the Supreme Court of California ruled that law enforcement officers can legally search text messages [JURIST report] on a suspect’s cell phone without a warrant incident to a lawful custodial arrest.