Boston police have used a controversial cellphone tracking technology 11 times over the past seven years without once a obtaining a search warrant, according to documents obtained through public records requests.

The tracker, which allows law enforcement agencies to pinpoint the location of a cell phone, are under legal challenge in a handful of states because police used them without warrants or hid their use from defendants.

Asked about the technology in a  radio interview on WGBH in February, Boston Police Commissioner William B. Evans said that officers normally obtain warrants to deploy the portable device known as a cell-site simulator, except in urgent situations where people’s lives are at stake. There is no explicit law in Massachusetts requiring search warrants for this type of technology, but a judge could potentially throw out evidence obtained through a tracker if it was deemed to be illegally obtained.

“When we have information that we have to get off a cell phone, we normally apply for a search warrant,” Evans said.

But the department did not obtain warrants in any of the 11 instances in which it deployed the tracker since 2009, when it purchased one of the devices, according to information released by police over the past four months to The Eye, a publication of the New England Center for Investigative Reporting, and to the American Civil Liberties Union of Massachusetts.

The department also used it another 11 times on behalf of outside agencies, but declined to identify them; city lawyers said those agencies may have sought warrants before asking the department for assistance.

A Boston police spokesman said on Tuesday that the 11 instances in which police used the tracker were emergencies, for which no warrant is needed, and that Evans’ statements in February did not contradict the latest information.

“He did not indicate that the BPD has used the technology pursuant to a warrant. He was indicating that obtaining a warrant is one way that the technology can be deployed, the other of course being exigent circumstances,” Lieutenant Detective Michael McCarthy wrote in an email.

Cell-site simulators — often referred to as “StingRays” — force nearby cellphones to connect to them by mimicking mobile phone towers. The tracker registers the location for each phone, so police can pinpoint it or track its movements.

Boston police have used the tracker three times to locate a missing person, twice on human trafficking cases, and another two times to investigate commercial robberies, according to the records. The remaining deployments were for investigations of a homicide, firearm possession, kidnapping, and to locate a fugitive.

Across the country, civil rights advocates have criticized police use of cellphone trackers without a warrant. Several states — Massachusetts not among them — have passed laws requiring the warrants.

The U.S. Department of Justice and Department of Homeland Security amended their policies last fall to require warrants when federal agents use the devices, with exceptions for emergencies, such as the need to pursue a fleeing suspect or prevent immediate death or serious injury.

Earlier this year, in responses to inquiries and records requests, the department said it first acquired its tracker in 2014, as The Eye and the Boston Globe  reported in February. But  documents provided by City Hall in April indicate that the 2014 purchases were actually upgrades for a cell-site simulator that the police already owned.

On each of the occasions when officers employed the tracker, it was used “solely to narrow down the location of the suspect and/or person in danger,” according to a joint response from City Hall and police in April.

A lawyer for the Boston Police Department, Nicole Taub, in a  letter responding to a public records request, told the ACLU of Massachusetts in March that the department “has not deployed the equipment pursuant to a search warrant.” In response to a request from The Eye, another Boston Police Department lawyer, Katherine Hoffman,  wrote in May that it “has not been able to identify any search warrant documentation” for use of the device.

Evidence excluded

Asked whether he was aware that the police had not obtained warrants in these tracking cases, Boston Mayor Martin J. Walsh responded in a statement, “The decision to deploy certain technology is made on a case-by-case basis by the police and always done within the requirements of the law.”

Determining the legality of evidence obtained during police investigations is the purview of the courts. In Maryland recently, an appellate court  ruled that Baltimore police were obligated to obtain a warrant to use a tracker in their efforts to locate a suspect wanted for attempted murder.

The court found in that case that police had violated constitutional protections against unreasonable searches. A Baltimore detective  testified in a different case last year that his department had used its cell-site simulator more than 4,000 times since 2007.

Earlier this month, a federal judge in New York City  excluded evidence that U.S. Drug Enforcement Agency officers gathered from a suspect’s apartment — narcotics, digital scales, empty plastic bags, and other drug paraphernalia — because officers failed to obtain a warrant prior to finding him with a simulator.

Additional court cases concerning trackers and warrants are pending in Washington D.C., and Milwaukee.

Jake Wark, a spokesman for the Suffolk County district attorney’s office, said that tracking a cellphone doesn’t always require search warrants. They “may be required in some cases but not in others depending on the duration of the tracking, the location of the target in a public space or private residence, any exigent circumstances that may apply, and any other forms of judicial authorization, such as arrest warrants, that may have been granted,” Wark said.

The revelation that the Boston Police Department did not get warrants when it used cellphone tracking devices raises “serious Fourth Amendment concerns,” said Jessie Rossman, an attorney with the ACLU of Massachusetts.

“The BPD’s troubling response to our records request highlights the importance of government transparency, particularly regarding cutting-edge surveillance tools,” she said.

In his February radio interview, Evans promised to release data on how often the tracker is used and for which types of investigations — a promise that he fulfilled in subsequent months.

The department declined to identify the outside agencies who had asked for assistance, but said there were a total of nine agencies — five state or local and four federal. In nine of the cases, the department was asked to assist with a drug investigation.

Police said that indicating which outside agencies have asked for assistance with cellphone tracking might assist criminals.

“[D]isclosing the jurisdictions where this equipment is utilized may result in the use of countermeasures to avoid detection by law enforcement in locations where this equipment is being utilized,” Taub  wrote to the ACLU of Massachusetts in April.

Taub indicated that she did not know whether the outside agencies obtained warrants before asking for Boston’s assistance.

The Eye is the online news site of the New England Center for Investigative Reporting, a nonprofit based at Boston University and WGBH News (PBS/NPR) in Boston.