About 3,000 people in Massachusetts are wearing court-ordered ankle monitors right now. And under a little-known agreement between police and probation officials, officers can use those monitors to see where many of those people are at any time.

It’s a longstanding practice for probation officials to keep track of people who have agreed to wear the monitors as a condition of their freedom. But police are also using the monitors to try to catch them committing new crimes.

Civil liberties experts say the situation raises questions about whether police can continue to scrutinize the movements of people who in some cases have not been convicted of anything.


The recent shooting of a Boston police officer during a traffic stop has dominated headlines for weeks. But one detail that has been largely overlooked is how that stop began.

One of the passengers in the car was Dennis A. Wilson, who was on GPS monitoring as he awaited trial on charges that included threatening a police officer, resisting arrest and driving without a license. Police wanted to talk to him about a shooting in Roxbury, and used his ankle monitor to find him.

Police say when they pulled the car over, Angelo West shot an officer in the face and other officers opened fire. West was killed. The officer, John Moynihan, was released from Boston Medical Center Saturday.

In a court hearing for Wilson — we’ll get back to the reason why he was in court — Suffolk County Assistant District Attorney Matthew Feeney said the practice of sharing the GPS information is a “routine occurrence.’’

GPS data is just like surveillance footage or witness statements or cellphone records, said Jake Wark, a Suffolk County District Attorney’s office spokesman. Investigators have an obligation to use it, he said, though it’s generally not crucial to a case.

“When that data is meaningful in an investigation, we’d be remiss not to use it,’’ he said.


But Wilson’s lawyer, Bill Lane, argued in court that it was a violation of his client’s privacy for the probation department to share his information with the police department, a separate entity.

“My client has a private interest in his position even though he’s enrolled in a GPS-monitoring program,’’ he told the judge. Lane declined to comment for this story.

An Explosion of Monitoring

The GPS-monitoring program in the Commonwealth has exploded since tracking devices were first attached to the ankles of about 100 sex offenders in 2005.

The next year, Boston became the first city in the Northeast to use GPS technology to track about 100 violent offenders in a pilot program. It’s since expanded to 3,000 parolees, pre-trial probationers and other offenders.

A probation office spokeswoman wouldn’t tell Boston.com exactly how often police use GPS information from probation officials, or how many of the 3,000 have had their whereabouts shared with police.

“Police departments occasionally request GPS information from the Massachusetts Probation Service for an ongoing criminal investigation,’’ said Coria Holland, a probation spokesman. “Police departments and the Probation Service are criminal justice agencies able to share information with each other in the course of their criminal justice duties, including to protect the public and supervise offenders in the community.’’

Lt. Michael P. McCarthy, a police spokesperson, said the department doesn’t comment on “investigative techniques that may or may not be used by the Boston Police.’’

Shared GPS information has led to arrests in several cases across the country. But the practice is new enough that it’s not on the radar of many privacy groups.


Even officials from the American Civil Liberties Union, typically at the forefront of privacy concerns, said they weren’t aware of the practice and therefore couldn’t comment for this story.

Hanni Fakhoury, senior staff attorney at the Electronic Frontier Foundation, said sharing GPS data seems especially questionable in cases like Wilson’s, where the person being tracked hasn’t been convicted of the charges that led to his GPS monitoring.

Fakhoury compared it to the collection of DNA from those charged but not convicted — something the U.S. Supreme Court has allowed for “identification purposes.’’

Ankle monitors are ostensibly for the purpose of making sure probationers are following the terms of their release, he said. But really “it’s another way to collect information about a person which they can use to connect to other crimes,’’ he said.

“You put the monitor on for one purpose and you use it for a separate purpose,’’ he said. “That’s what’s always lurking in the background.’’

‘Dream’ Evidence

Being tracked isn’t always bad for suspects, said Holland, the probation spokeswoman. In some cases, it may even provide them an alibi. GPS data could show, for example, that a suspect was across town when a crime occurred.

There’s also an obvious societal benefit to police capturing criminals. That’s exactly what GPS data helped them do in several cases in Massachusetts and across the country.

Jeremy Morin was convicted of arson after GPS data from his ankle monitor — attached after a previous arson case — placed him at the scene of another fire in Springfield.

An Indianapolis man already on probation for robbery was arrested when his monitor showed him at 10 stores that were robbed in a week. A similar arrest happened in Los Angeles.

In San Diego County, police worked with customs agents to track and arrest a man suspected of breaking into a woman’s apartment. He was wearing a GPS ankle monitor as he awaited a deportation hearing.

And a South Carolina man accused of trying to steal an officer’s gun was found at his brother’s home through his court-ordered ankle monitor.

A Colorado prosecutor called it a “dream’’ to have GPS linking a suspect to several burglaries.

But it’s still unclear how common the practice is — or may become — nationwide.

A Warrantless Search?

The sharing of information between police and probation smells like a warrantless search, said Rosanna Cavallaro, a professor at Suffolk University Law School.

“There is a state agency that is legally permitted to collect that information — probation,’’ she said. “That doesn’t mean they’re permitted to share it with any other state actor.’’

The U.S. Supreme Court ruled in 2012 that police could not attach a GPS device to a suspected drug trafficker’s car, because that constituted a search.

But what about people on probation? Do they give up their right to privacy because they’ve been ordered to wear a GPS monitor?

No, says defense attorney Martin G. Weinberg. “I don’t think being on probation extinguishes all privacy rights,’’ he said.

“The tracking device meant to prevent someone from fleeing a jurisdiction cannot be converted into 24-hour surveillance,’’ he added.

Others are less sure. Agreeing to wear a GPS monitor means you’re giving up some privacy, said Norman Zalkind, a Boston defense attorney.

“You’re saying, ‘I’m going to follow the rules and only go where I’m supposed to go,’’’ he said.

Still, the police should have a good reason to get the data, Zalkind said.

Weinberg says it’s only a matter of time before a case like this goes in front of the Massachusetts or U.S. Supreme Court for a final determination.

“In baseball terms,’’ Weinberg said, “we’re in the top of the second inning of courts making these delicate judgements about how far and how intrusive we’ll allow non-physical, non-visual surveillance.’’

An Unavoidable Violation

Wilson has not been charged with any new offenses — not in the Moynihan shooting nor in the separate shooting police wanted to talk to him about in the first place.

His GPS data became an issue during a hearing on whether he had violated a curfew that was part of his pre-trial probation.

The reason for his violation, according to his lawyer: He was in police custody. The shooting occurred at 6:40 p.m., but Wilson was held by police past his 7 p.m. curfew.

He has the ankle monitor to prove it.