Washington ( CNN ) -- Police erred by not obtaining an extended search warrant before attaching a tracking device to a drug suspect 's car , the Supreme Court said in a unanimous ruling Monday . A majority of justices said that secretly placing the device and monitoring the man 's movements for several weeks constituted a government `` search , '' and therefore , the man 's constitutional rights were violated . Four other justices also concluded that the search was improper but said it was because the monthlong monitoring violated the suspect 's expectation of privacy . U.S. Supreme Court rules on health care challenge | On humane treatment of downed livestock . That difference of legal analysis may create further confusion among law enforcement over when and for how long such high-tech operations can be used , on both criminal suspects and the general public . At issue was whether movement in a private vehicle on city streets is `` public '' in nature . Growing sophistication of electronic devices to monitor the movements of suspects made this issue ripe for review , since lower courts had disagreed on when such surveillance is permissible without a warrant . The devices send an electronic signal to a satellite , allowing real-time plotting of someone 's whereabouts . Antoine Jones was a co-owner of Levels , a Washington nightclub , when he was suspected of trafficking cocaine on the side . A joint FBI-D.C. police team covertly attached a GPS device to his Jeep outside the terms of a warrant . A warrant had been granted , but installation of the GPS device was authorized by a judge only within 10 days and only in the District of Columbia . Agents waited until the 11th day to secretly place it on the vehicle , and they did so in neighboring Maryland . Jones was then monitored for 28 days as he drove around the area . He was eventually tracked to a house where law enforcement officers discovered nearly 100 kilograms of the illegal narcotic , along with about $ 850,000 in cash . Jones was sentenced to life in prison . The court was being asked to decide whether such covert surveillance violated the Fourth Amendment and whether in this case it should be considered a `` search , '' a `` seizure '' or both . The justices agreed police violated Jones ' rights but disagreed on just why . The Constitution 's Fourth Amendment says , `` The right of the people to be secure in their persons , houses , papers , and effects , against unreasonable searches and seizures , shall not be violated . '' Antonin Scalia wrote for a five-vote majority that a person 's property is legally sacred , and the government had to justify placing a GPS device on the vehicle . Scalia said the electronic age does not change a centuries-old concept . `` The government physically occupied private property for the purpose of obtaining information , '' said the ruling . `` 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 . '' Chief Justice John Roberts and Justices Anthony Kennedy , Clarence Thomas and Sonia Sotomayor agreed with the conclusions . But a group of four justices led by Samuel Alito concluded that the majority 's reasoning was `` artificial '' and did not address larger legal concerns of searches in the digital age , including GPS . He said the court should have used this case to clarify the limits of police monitoring of wireless personal communication devices like mobile phones and Internet use . `` The availability and use of these and other devices will continue to shape the average person 's expectations about the privacy of his or her daily movements , '' Alito wrote . `` In circumstances involving dramatic technological change , the best solution to privacy concerns may be legislative . '' But the U.S. Congress and most states have not kept up with the times , Alito said , leaving courts to sort out what level of privacy a citizen can expect . He said that in this case , four weeks of tracking was more than enough to justify police getting a search warrant . Alito was backed by Justices Ruth Bader Ginsburg , Stephen Breyer and Elena Kagan . The justices have another pending case they may decide to tackle , from an Oregon inmate who faced similar circumstances . Police there had attached a GPS device to Juan Pineda-Moreno 's car while it was parked on his property . Officers then tracked him to a remote marijuana field he was cultivating . He was convicted and sentenced to more than four years behind bars . Unlike in the Jones case , a federal appeals court in San Francisco ruled that this was not a `` search , '' so no warrant was required to place the device on Pineda-Moreno 's Jeep Cherokee . His conviction was upheld . The justices have not taken any action on the Oregon appeal , perhaps waiting to resolve the issue with Jones ' appeal from Washington . The current case is U.S. v. Jones ( 10-1259 ) .
Following a car for weeks via a tracking device requires a search warrant , justices say . The justices are divided on what they say makes the action unconstitutional . Justice Alito , for the majority , cites the `` physical intrusion '' of placing the device . " Comment: It's not illegal to use GPS in your vehicle if you're following someone who isn't being followed by police or other law enforcement officers ( e.g. driving down an interstate ) and it