Congressional lawmakers called on local police departments Wednesday to embrace new federal policies intended to rein in the use of a cellphone tracking device at the center of a widespread review of criminal cases in Baltimore.
Members of the House Committee on Oversight and Government Reform offered a tepid endorsement of the Obama administration's federal guidelines for using the surveillance tool known as a stingray, but expressed concern that the policies do not apply to local police.
Baltimore has been at the center of a national debate over the use of the device after revelations that city police have relied on the technology 4,300 times since 2007, often without obtaining a search warrant. Defense attorneys and prosecutors are reviewing thousands of criminal cases involving the trackers.
The Department of Homeland Security and the Justice Department — which oversees the FBI — say they now require their agents to obtain a warrant based on probable cause in most cases before using the device.
But requirements for local police — who purchase the equipment independently of the federal government — are less clear. Members of Congress, who are considering legislation to address privacy concerns raised by the technology, noted that the federal policies have little bearing on city police.
"These agency policy changes ... do not meaningfully restrict state and local officials," Rep. Ted Lieu, a California Democrat, said Wednesday at a hearing of the House Oversight subcommittee on information technology. "I hope that state and local law enforcement agencies follow the lead of these federal policies and implement stringent privacy protections and legal standards."
The stingray — a suitcase-size device — can sweep up basic cellphone data from a neighborhood by tricking phones into believing that it is a cell tower, enabling it to identify unique subscriber numbers. The data is then transmitted to the police, helping them determine the location of a phone without the user even making a call or sending a text message.
When police and prosecutors began using the device, they signed a nondisclosure agreement with the FBI in which they agreed not to discuss it. Prosecutors have agreed to drop cases rather than disclose information about the technology.
That has prompted an outcry from defense attorneys and privacy advocates. The Baltimore public defender's office said in August that it plans to review nearly 2,000 cases in which police used the device without defense attorneys' knowledge, and decide whether to challenge them.
An attorney in the public defender's office did not respond to a request for comment.
A Justice Department official said Wednesday that the Obama administration is renegotiating the terms of its nondisclosure agreements with local law enforcement agencies.
"Those agreements are intended to protect particularly sensitive information about the operation of the technology, the capacity of the technology," Elana Tyrangiel, principal deputy assistant attorney general, told lawmakers Wednesday. "They're not meant actually to preclude more transparency in terms of disclosing that they've been used in any particular case."
A spokeswoman for State's Attorney Marilyn J. Mosby has said Baltimore's agreement was signed by her predecessor and that the office does not believe it is bound by it.
Baltimore police have said they obtain court orders before using the device, but critics have noted the difference between search warrants and court orders for "pen registers," which rely on a less stringent legal standard. Police traditionally have used pen registers to access phone log information maintained by cellular companies.
A Baltimore police spokesman declined to discuss the department's current policy or say whether officers are securing search warrants before using the device.
"We will act in accordance to the law and best practices with the use of any technology or crime-fighting tool," police spokesman T.J. Smith said in a statement. "We continue to monitor any changes in laws or best practices in law enforcement regarding this technology or any other."
Rep. Will Hurd, the Texas Republican who chairs the information technology subcommittee, called the federal policies a "big step forward" but noted "lingering concerns about the substance" of the guidelines, including large, ambiguous exemptions, such as for "exceptional" situations.
"I remain troubled that federal law enforcement is still not embracing transparency the way they need to in 2015," Hurd said. "Secrecy is a double-edged sword."
Tyrangiel said the Obama administration policies apply to local departments when federal and local law enforcement are working together, but the federal government has little ability to force its guidelines on local agencies in other cases.
Tyrangiel said the Justice Department hopes its policy will serve as a model for state and local police.
David Rocah, senior staff attorney at the ACLU of Maryland, said the focus on local police is "absolutely necessary because there are far more of these devices in use at the local level than at the federal level."
"And the privacy issues surrounding their use — and what happens to the data — are equally if not more critical with respect to local law enforcement than for federal agencies," he said.
Baltimore Sun reporter Justin Fenton contributed to this article.