Is there an expectation of privacy on public roads?

Gordon Crovitz:

Technology has changed how information flows, how people communicate, and even the meaning of "friend," which has become a verb. Now, add to the imperial reach of technology the power to rewrite constitutional protections.

A case argued last week in the Supreme Court hinges on what Americans consider "reasonable" under the Fourth Amendment's prohibition of unreasonable searches and seizures. Not even Mark Zuckerberg of Facebook has always correctly anticipated how much privacy people expect, so imagine how hard this is for nine people trained as lawyers, not engineers or online marketers.

The justices did their best. The facts of U.S. v. Antoine Jones are that District of Columbia police, working with the FBI, suspected a nightclub owner of being a drug dealer. They installed cameras near Antoine Jones's nightclub, got his cellphone records, and attached a GPS tracking device to his Jeep Grand Cherokee. In 2005, acting on the information they had gathered, police executed a search warrant and found a huge stash of cocaine, firearms and cash. The defendant's lawyers objected to the GPS, saying that tracking car movements over several weeks violated his expectation of privacy.

The Fourth Amendment is a rare part of the Constitution that explicitly requires judges to adjust standards to reflect changes in society. What was unreasonable before may be reasonable now. Most adults in the U.S. have created Facebook accounts, which disclose more information than the most avid gossip-monger could have produced in the days before social media.

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During the oral argument in last week's GPS case, Justice Samuel Alito defined the issue well: "Maybe 10 years from now, 90% of the population will be using social networking sites, and they will have on average 500 friends, and they will have allowed their friends to monitor their location 24 hours a day, 365 days a year, through the use of their cellphones," he said. "What would the expectation of privacy be then?" 

Technology makes it easier for law enforcement to gather information, even as we expect more information to be public. "In the pre-computer, pre-Internet age most of the privacy that people enjoyed," Justice Alito noted, "was not the result of legal protections or constitutional protections. It was the result simply of the difficulty of traveling around and gathering up information." 

Several justices noted that authorities could have tracked the suspect's car if enough police officers devoted enough effort to follow him. Justice Anthony Kennedy told the defendant's lawyer: "What you're saying is that the police have to use the most inefficient methods." Put another way, wouldn't most Americans think it unreasonable to lock law enforcement into earlier generations of technology when criminals use the latest technology?
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I think using the GPS tracking device was reasonable.  The guy was using public streets and highways.  No one would argue that he could take his clothes off and run down the street (unless he was in San Francisco). The point is that there is no expectation of privacy in public places.