A “StingRay II,” made by the Harris Corp., can redirect cellphone calls away from cell tower antennae and capture their identifying data and location. Police use them to find people. Some argue that it’s an invasion of privacy. (Courtesy Harris Corp.)

Prince Jones was sitting in his car on Minnesota Avenue in Northeast Washington one morning in October 2013 with a prepaid cellphone and four other cellphones that had been stolen from three women in recent sexual assaults. With help from two phone companies, D.C. police were able to narrow down the general location of the phones. And then with the use of a “StingRay” device, investigators were able to pinpoint the location of the phones — and Jones. He was arrested and later convicted of sexual assault, kidnapping and armed robbery.

Police and federal agents around the country have for years been quietly using cell-site simulators in which a portable device intercepts signals from cellphones attempting to connect with cell towers and then captures their identifying numbers and precise locations. Defense lawyers and civil libertarians claim that the devices are the equivalent of a police search and, therefore, require a search warrant.

Last year, a Maryland appeals court agreed and ruled that Baltimore police could not use evidence collected by a cell-site simulator in an attempted-murder case. On Tuesday, the District’s highest appeals court heard oral arguments on the Jones case and is ready to be the second appellate court in the nation to weigh in on whether capturing an individual’s cell signal is covered by the Fourth Amendment’s prohibition against unreasonable searches and seizures.

Of the three judges on the D.C. Court of Appeals panel, only Judge Phyllis D. Thompson seemed to indicate which way she was leaning Tuesday. The fact that Jones was still carrying the stolen phones from his victims complicated his expectation of privacy, Thompson said, and, in fact, created the expectation that someone would try to find them, or him. “It’s difficult for me to see that he has a reasonable expectation of privacy that we’re prepared to recognize as legitimate,” Thompson said.  Judges Corinne A. Beckwith and Michael W. Farrell gave fewer indications of their leanings.

Stefanie Schneider of the Public Defender Service acknowledged that searching for the victims’ phones was a different question. At Jones’s trial, police initially testified that they located Jones by searching for the victims’ phones, but eventually it was revealed that the StingRay had actually located Jones’s phone. (The phones are tracked by identification numbers, not phone numbers.)

Prosecutors argued, and the trial judge agreed, that the police would have eventually searched for the victims’ phones and that “inevitability” negated the need for a warrant, though detectives did not know the name or location of the suspect.

“I’m not saying the police can’t track the stolen phones,” said Schneider, the public defender. “What I’m saying is the police can’t track the defendant’s personal property.”

Thompson responded that “the fact that he’s traveling with stolen goods changes the calculus.”

Schneider answered: “His privacy rights are the same, whether he’s carrying stolen property or not. I’m not aware of any case law that somebody who has committed a crime has relinquished their property rights.”

In Baltimore in 2014, police had obtained a warrant for Kerron Andrews on an attempted-murder charge but couldn’t locate him. A cellphone company gave police a general location, and then police used a cell-site simulator called “Hailstorm” to find the exact house where the suspect was staying. Officers were allowed into the home, where Andrews was sitting on a couch with the phone in his pocket. Police then obtained a search warrant for the house and found a gun in the couch cushions.

The trial judge in Baltimore suppressed the search. In March 2016, the Maryland Court of Special Appeals upheld that ruling, with the opinion written by Judge Andrea M. Leahy.

We conclude that people have a reasonable expectation that their cell phones will not be used as real-time tracking devices by law enforcement, and — recognizing that the Fourth Amendment protects people and not simply areas — that people have an objectively reasonable expectation of privacy in real-time cell phone location information. Thus, we hold that the use of a cell site simulator requires a valid search warrant, or an order satisfying the constitutional requisites of a warrant, unless an established exception to the warrant requirement applies.

With increasing public concern over the government’s potential use of new technologies to invade citizens’ privacy, police agencies began using cell-site simulators with very little fanfare, and sometimes they only reluctantly acknowledge their use. In the Baltimore case, the appeals court criticized city police and prosecutors for using the technology and for signing an agreement with the FBI and device manufacturers to never disclose its existence to the public, courts or defense counsel. Other law enforcement agencies across the country have entered into the same secrecy deals, according to information gleaned through litigation or public records requests.

Nathan F. Wessler of the American Civil Liberties Union, which filed an amicus brief and argued in the case Tuesday, said that an FBI agent sat with prosecutors at Jones’s trial in Washington to instruct police officers which questions to answer and not answer about the use of the StingRay. The Justice Department has since issued policy guidelines to federal agents instructing them to get search warrants before using cell-site simulators, Wessler said, but the guidelines are not binding on local police and could be rescinded by the new attorney general, Jeff Sessions.

Farrell noted that the devices gather information not only on the targeted phone but on all phones in the area, which are redirected away from network cell towers. The simulators also disrupt all calling and texting ability for the phones that are redirected. Lawyers in the Jones case realized that Jones’s phone had been tracked because he was in the middle of a call that dropped and then tried seven times without success to redial the person he’d been speaking with.

Assistant U.S. Attorney Lauren R. Bates argued that Jones “is on a public street. He has stolen goods. He is actually using the cellphone he used to set up multiple sexual assaults and robberies. Everybody knows cellphones send out signals and provide location information.”

Farrell asked, “You have no reasonable expectation that’s going to end up in the lap” of the D.C. police?

Bates answered, “You don’t have a reasonable expectation of privacy in that information you’re sending out.” She noted that every fleeing felon on TV or in movies knows to toss away or smash their cellphone so they can’t be tracked.

Farrell then observed that it seems almost accepted, “just the notion, in this day and age, you power on your cellphone and you basically relinquish any expectation that your whereabouts are going to be kept secret outside of your residence.”

The judges did not indicate when they would issue a ruling.