ST. LOUIS • St. Louis police acknowledged this month that they are using a controversial device that allows them to track cellphones, but won’t name the brand or explain how it works, according to court documents filed last week.

In a motion filed May 19, Natasha Alladina, a public defender in St. Louis, wrote that city police Detective Aaron Harwood refused to provide more information in a May 6 deposition, citing a nondisclosure agreement. Harwood did say that police had obtained a signed court order that he used to track a victim’s stolen cellphone with a cell site simulator.

A simulator, often called by one of the brand names, StingRay, can mimic a cell system tower, or screen data flowing through it, allowing a cellphone to be tracked by authorities.

It’s difficult to tell if this is the first case in which St. Louis police have admitted the use of the devices, and the method by which they obtain a judge’s approval. A spokeswoman for the St. Louis circuit attorney’s office did say that it was the only pending legal challenge of which she was aware.

But a series of legal challenges to the use of the technology is in the works in St. Louis after an Alladina colleague and other defense lawyers spotted some vague language in a police report last year that led them to suspect that a StingRay had been used.

Those suspicions led to questions, but the case against three men accused of robbing seven people in 2013 was dismissed before a member of the police intelligence unit could be deposed for more detail.

A co-defendant withdrew her guilty plea and prosecutors then dropped that case.

Prosecutors have insisted that the dismissals were unrelated to the StingRay challenge.

Harwood’s statements come at a time when the FBI has relaxed the rules a little on what police can say about the technology.

Police are required to sign nondisclosure agreements with the FBI before getting approval to buy StingRay-type devices. Agreements revealed elsewhere say police vow not to reveal any information about the equipment without the FBI’s written approval, even in court. Prosecutors elsewhere have dropped cases rather allow police to discuss StingRay use.

FBI spokesman Christopher Allen told the Post-Dispatch last month that the existence of the technology is not considered sensitive — just the way it works.

He provided a statement Friday that said, in part, that the nondisclosure agreement “should not be construed to prevent a law enforcement officer from disclosing to the court or a prosecutor the fact that this technology was used in a particular case. Defendants have a legal right to challenge the use of electronic surveillance devices, and not disclosing their use could inappropriately and adversely affect a defendant’s right to challenge the use of the equipment.”

Last week, Allen told the Washington Post that the FBI has not invoked a provision of the agreements that would force officials to drop a criminal case.

But simply acknowledging the use of StingRays will not be enough for defense attorneys.

In her motion, Alladina says the way they work must be turned over in a case where she represents a defendant, as well as the FBI nondisclosure agreement. She wrote that the “mechanics of the cell site simulator technology are particularly relevant in this case because the cell site simulator provided the entire probable cause to arrest Defendant at the apartment where the stolen phone was found.”

She said the agreement could shed light on whether police are bound “to answer trial questions in an FBI-approved way, and the NDA (agreement) may outline the consequences of breaching the contract.”

At issue in the case of Alladina’s client, Anthony D. Agnew, 24, is a stolen cellphone. Charging documents say that two men who were trying to sell speakers on Craigslist were robbed at gunpoint on Nov. 13 of their cash, cellphones and vehicle. Agnew was found in possession of one of the stolen phones and then admitted taking it, charging documents claim.

A hearing for Alladina’s motion is scheduled for June 4.

The FBI has refused to provide a list of area police departments that use StingRay-type technology. In response to a Sunshine Law request, a St. Louis County police spokesman on Thursday told the Post-Dispatch that the department does not own such a device nor has ever completed paperwork to acquire one.

Robert Patrick • 314-621-5154

@rxpatrick on Twitter

RPatrick@post-dispatch.com

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