( CNN ) -- On Tuesday , the Supreme Court will confront the profound impact of new location-tracking technologies on Americans ' privacy . The case , U.S. v. Jones , presents the question of whether law enforcement needs a warrant before planting a GPS tracking device on a person 's car . The answer to this question is important in its own right , but the case is likely to have broader implications . Attaching a GPS to a car is n't the only way the government can track people 's movements . In fact , everyone with a cell phone is already carrying a device that the government can use to track his or her location . As a result , the principle at stake in this case may well shape our privacy rights in the years and decades to come . The police in the current case suspected Antoine Jones of drug violations and tracked his movements continuously for one month by installing a GPS device on his car . Increasingly , though , law enforcement agents are tracking our movements by tracking the cell phones that most people are already carrying around . It does n't matter whether your phone is a smartphone or whether you use it to make calls ; as long as your phone is turned on , it registers its location with cell phone networks several times a minute , and all U.S. cell phone companies hold on to that data , some of them for years . This kind of tracking is extremely invasive , because if the government knows where you are , it knows who you are . As the Jones appellate court explained in its ruling that the government violated the Fourth Amendment , `` A person who knows all of another 's travels can deduce whether he is a weekly churchgoer , a heavy drinker , a regular at the gym , an unfaithful husband , an outpatient receiving medical treatment , an associate of particular individuals or political groups -- and not just one such fact about a person , but all such facts . '' Cell phone tracking can reveal our private associations and relationships with one another . The government could make note of whenever people being tracked crossed path or spent time together , showing who our friends , associates and lovers are . The Justice Department sometimes gets warrants to track location , and some local police departments make it a policy , which shows that it 's not an unworkable requirement . But state and federal judges across the country have made conflicting rulings on what standards are required for the government to obtain tracking information from cell phone companies . New technology provides the government with a powerful and inexpensive tool to follow individuals as they travel through both public and private areas . Unless the court concludes that such tracking requires a warrant , anyone 's movements could be subject to remote monitoring and permanent recording at the sole discretion of any curious police officer , without any judicial oversight . And while it may not be realistic to think that the government will install a GPS device on every car , it 's not at all implausible to think that the government will ask cell phone providers to turn over location-tracking information en masse -- and it may well be the case that the government is doing so already . It was revealed last month that the London police have a system that lets them track hundreds of phones in real time in a targeted geographic area , a technology that could easily enable the government to identify everyone at an Occupy protest , tea party rally or any other political gathering . The genius of the Constitution is that its limits on the government can still be applied in a modern world that the framers could scarcely have imagined . Anyone who values privacy should hope that the Court ensures the government can not use technological advances to undermine the liberties this country was founded on . The opinions expressed in this commentary are solely those of Catherine Crump .
Does law enforcement need a warrant before planting a GPS tracking device on a car ? Yes , the Supreme Court has to decide that they should , says Catherine Crump . The privacy at stake in a current case may well violate our privacy rights , she says . All of us can already easily be tracked through our cell phones , Crump says .