In positive Fourth Amendment news, the South Dakota Supreme Court this week reversed a drug conviction and declared that police need a warrant to use GPS transmitters to secretly track citizens.
According to the unanimous ruling in South Dakota vs. Elmer Wayne Zahn, Jr., police had plenty of reason to think Zahn was dealing marijuana. They'd found lots of spare cash and containers smelling of pot in the bedroom where Zahn's wife died in June, 2008. In November 2008, police arrested Zahn for DUI and found marijauna and $10,000 in cash in his car. That stop resulted in Zahn's pleading guilty to DUI and possession of pot and paraphernalia.
Then in March 2009, Aberdeen policeman Tanner Jondahl attached a magnetic GPS tracker to Zahn's vehicle. Police tracked Zahn's every vehicular movement for 26 days, including several trips to two storage units and a trip to Gettysburg, which was a bad idea, since Zahn was out on bond at the time and wasn't supposed to leave Brown County. Oops. The police rearrested Zahn, got a search warrant for the storage units, and found in one of them a hidden freezen with pot. That evidence led to another conviction, including intent to distribute.
Zahn appealed that conviction, saying the court should have thrown out the evidence discovered thanks to the GPS tracking. Our justices agreed:
...The GPS device used in this case continuously transmitted the geographic location of Zahn's vehicle to a computer at the Brown County Sheriff's Department. It enabled officers to not only determine his speed, direction, and geographic location within five to ten feet at any time, but to also use the recorded information to discover patterns in the whole of his movements for nearly a month.
[¶28.] When the use of a GPS device enables police to gather a wealth of highly-detailed information about an individual's life over an extended period of time, its use violates an expectation of privacy that society is prepared to recognize as reasonable. The use of a GPS device to monitor Zahn's activities for twenty-six days was therefore a Fourth Amendment search under the Katz "reasonable expectation of privacy" test [South Dakota v. Elmer Wayne Zahn, Jr., South Dakota Supreme Court, opinion filed 2012.03.14].
Cops can still watch what you're doing in public. They can still follow you down the highway in the cruiser. But the Court sees a problem with moving beyond observing individual public movements and secretly gathering a comprehensive picture of every move citizens make.
Police can still use GPS tracking devices; citing U.S. v. Garcia, the justices say that "The Fourth Amendment 'cannot sensibly be read to mean that police [should] be no more efficient in the twenty-first century than they were in the eighteenth' century." However, to conduct such a thorough search, police must first get a warrant.