Mobile phones were once the exclusive domain of business moguls. Today, even 10-year-old kids have cellphones. Increasingly, law enforcement is using that fact to track the whereabouts of suspects and obtain data about private communications.

But civil rights defenders and criminal defense lawyers are pushing back. In particular, they are challenging the use of cell tower simulators as warrantless searches in violation of the Fourth Amendment. The U.S. Supreme Court has just taken up a related cellphone case that may have broad implications for those accused of crimes.

Stingray technology enables cops to track cellphone users

Law enforcement agencies across the country are using Stingray cell tower simulators to find or follow citizens suspected of crimes. (To be fair, police have used the same technology to locate missing persons.) The Stingray machine intercepts the cell tower “ping” that cellphones emit even if the phone is in your pocket or turned off. It can track a person down to a specific location, and reveal where the phone user has traveled. The most advanced Stringray units can intercept calls and texts, or access information stored on smartphones.

The American Civil Liberties Union has created a nationwide map of state and local police departments (and a list of federal agencies)  known to use cellphone tracking devices. They are used by police in at least 24 states, including North Carolina and Georgia. The ACLU says it is “unknown” if any law enforcement agencies in South Carolina use Stingrays – many departments are secretive or cagey about whether they use such technology. They don’t want to tip off criminals or invite scrutiny from privacy watchdogs.

Courts are examining the legality of cell phone tracking

Some states require warrants before police can use cell tower simulators. And even then, a warrant is not a magic pass. A federal appeals court recently reversed a conviction that stemmed from a cell phone warrant. The judges ruled that police could not obtain a warrant merely on the presumption that a person has a cellphone and the possibility the phone may have incriminating evidence.

Now the U.S. Supreme Court will review a case, Carpenter v. United States, which hinged on cell tower location. The robbery suspects were convicted, in part, on evidence that their cellphones were used in the vicinity of the crime at approximately the time of the crime.

The Court will consider whether cellphone pinging and cell phone location data is fair game for law enforcement, or whether it requires a warrant. The case will have major implications because the technology has evolved to allow police to pinpoint a person’s location and movements, in real time.

The Fourth Amendment matters

The Fourth Amendment is not a “technicality.” The constitutional right against unreasonable search and seizure is one of the bedrocks of our criminal justice system. Just as law enforcement embraces technology to keep up with criminals, it is important to hold the police in check to ensure they are not abusing citizens or using technology to overreach their authority.