WILMINGTON, Del. — Federal officials are backing the Delaware State Police against a Freedom of Information Act request for information about how law enforcement uses cell site simulators.

Lawyers for the U.S. Department of Justice filed a “statement of interest” last week in a Superior Court lawsuit filed by the American Civil Liberties Union on behalf of a Delaware man. The suit challenges the refusal of state officials to provide details about DSP’s purchase and use of the technology, which mimics a cell phone tower in order to connect with and collect information on nearby cell phones.

“Although the United States is not a party to this case, it has a direct interest in the protection of the information withheld by the DSP,” DOJ attorneys wrote. “Cell site simulator technology is a key tool in the Federal Bureau of Investigation’s investigation, interdiction, and suppression of criminal and terrorist activity. Disclosure of even minor details about this technology will jeopardize, if not vitiate, the ability of the FBI and the larger law enforcement community to successfully deploy this valuable technology to locate criminals and terrorists, and recover victims.”

The Justice Department filing prompted a judge to indefinitely postpone arguments that had been scheduled for Wednesday.

Judge Richard Cooch said the DOJ’s statement and an accompanying declaration by FBI agent Russell Hansen, chief of the agency’s tracking technology unit, offers facts that were not previously in the record.

The judge invited both sides to submit motions on whether he should to consider facts in Hansen’s declaration, give the ACLU a chance to seek additional information and perhaps depose Hansen; and whether the federal filing should be remanded to the state attorney general’s for further consideration regarding an opinion it issued that led to the lawsuit. Oral arguments on the underlying appeal will come later.

After state police denied his FOIA request in its entirety last year, citing a nondisclosure agreement with the FBI, Jonathan Rudenberg filed a petition with the attorney general’s office. Following consultation with the FBI, the state police agreed to provide copies of 10 heavily redacted purchase orders, hiding the makes and model numbers of the cell site simulator equipment and component parts as well as product names of the accompanying software.

“The FBI redacted the names of the software on the purchase orders and is vehement that this information is proprietary,” deputy attorney general Rae Meredith Mims explained in an April 22 email to ACLU attorney Ryan Tack-Hooper. “Moreover, the release of the specific model names may allow individuals to develop technologies to impede or negate the operation of particular cell site simulator systems.”

While the attorney general’s office did order state police to provide a copy of the FBI nondisclosure agreement, Rudenberg argues that the attorney general’s office erred in not requiring the disclosure of unredacted purchase orders, in accepting the police agency’s representations that there were no other responsive documents, including any correspondence with equipment provider Harris Corp., and in not giving him a chance to respond to the submissions made by state police in response to his petition.

The attorney general’s office argues that Rudenberg has been given all the records to which he is entitled, and that Delaware State Police did not violate the Freedom of Information Act.