Georgia’s deputy attorney general said in court that he didn’t think police in the state were using Signal to communicate about the law enforcement training center colloquially known as “Cop City” – despite being presented, in a motion from defense attorneys, with evidence from the Guardian of law enforcement leadership ordering officers to download the encrypted phone app last year for that very purpose.

Defense attorneys have been seeking the Signal messages from Atlanta police and other law enforcement agencies that may be relevant to their clients’ cases from the deputy attorney general, John Fowler, since February, according to their 15 March motion.

Fowler did not respond, indicating only “that the Signal messages were not in possession of the state”, the motion said. He repeated the claim in court this week, saying he thought only federal agencies collaborating with the Georgia prosecution used Signal.

It is unclear if the official is not telling the truth, or doesn’t know how the arresting agencies in his office’s effort to prosecute 61 people tied to opposition against Cop City communicate with each other.

“We are unable to comment due to pending prosecution,” wrote the attorney general’s spokesperson Kara Murray in reply to queries from the Guardian.

The revelation came in a Fulton county superior court conference for prosecuting and defense attorneys to hash out details in the state’s pending Rico – or criminal conspiracy – case centered on Cop City. It is the largest Rico case in connection with a protest movement ever, experts have told the Guardian.

The fight against Cop City has drawn national and global headlines, particularly since 18 January of last year, when state troopers shot and killed Manuel Paez Terán, known as “Tortuguita”, who was camping in protest at a public park near the Cop City site – the first such incident in US history. Opposition to the project has come from a wide range of local and national supporters, with concerns such as unchecked police militarization and clearing forests in an era of climate crisis. Atlanta police say the center is needed for “world-class” training.

Fulton county superior court judge Kimberly M Esmond Adams said on Tuesday she planned to start trials in the Rico case before the year’s end, with five defendants at a time. Her job in court included ensuring the state finishes releasing its evidence to the dozens of defense attorneys involved in the case as soon as possible – after the state announced in November it had five terabytes of evidentiary data, the equivalent of about 400m pages of text, or 800,000 digital photos. On Tuesday, the state said it may have up to a terabyte more worth of data.

At one point, Judge Adams appeared to lose patience with the state, saying: “You all indicted 61 people, so you don’t get to come tell me that you’re having issues with getting evidence” – and gave until 17 May for the state to have all discovery materials filed.

That data should include Signal messages, defense attorney David Gastley asserted in his 15 March motion and, again, in court on Tuesday. He named the Guardian’s 4 December 2023 reporting as the main exhibit supporting the request. Based on emails obtained through open records requests, that story established how top Atlanta police officials began setting up Signal groups in early 2023 to discuss Cop City.

In one email described in the Guardian’s reporting, on 23 January Maj Jessica Bruce of the Atlanta police informed a dozen agencies: “As we get closer to the building of the Acadamy [sic] I wish to keep everyone informed in a timely manner” – and that she would be adding everyone receiving the email to a Signal group. The “Acadamy” is Cop City.

That email was sent to police departments in Atlanta and in Cobb and DeKalb counties – part of the Atlanta metro area – as well as the Georgia bureau of investigation, the FBI and the ATF. Police from the Norfolk Southern railroad were also copied.

Gastley asked in a 13 February email to the attorney general’s office for “preservation and production” of “[a]ll messages pertaining to the ‘Stop Cop City’/‘Defend the Atlanta Forest’ investigation and prosecution exchanged by law enforcement on … encrypted messaging apps such as Signal and WhatsApp”.

He named all police officials and agencies mentioned in the Guardian’s reporting, asking for communications between them. He also asked for all communications about the decision to use the app, and about any policies governing its use.

“It is implausible that there are no relevant witness statements contained on these large-scale, inter-agency Signal group threads designed to communicate about the Cop City protests,” the 15 March motion reads.

Despite five emails and an in-person visit, the attorney asserts, Fowler did not respond – except to say that he didn’t think the state had any such messages, but had “a willingness to consider complying with the request”, according to the motion.

The defense attorney sums up these events in the motion, raising the possibility that messages have been deleted: “[C]ommunications with the Attorney General’s Office suggest that there has been no diligent inquiry to determine the extent of discoverable materials contained within the tranche of law enforcement Signal messages (to the extent these messages have not been deleted).”

With Signal, users can set the app to automatically delete messages, at which point they are not even available for retrieval on computer servers, as with standard texts. First amendment and digital transparency experts told the Guardian in December that police or other government officials using encrypted apps like Signal to communicate about official business raises serious concerns about the ability to access information afterward, in accordance with “freedom of information” and open-records laws – and now, possibly, in response to discovery requests in state prosecutions.

The defense attorney’s motion also notes in a footnote how the state’s own 109-page Rico indictment refers to the use of Signal by activists against Cop City. Their “communication is often cloaked in secrecy, using sophisticated technology aimed at preventing law enforcement from viewing their communication and preventing recovery of the information”, the indictment reads.

“In the indictment of this case, the State itself chose to include the use of the Signal messaging platform as alleged inculpatory evidence against the defendants’ purported ‘enterprise’,” the motion reads. “Surely, the extent to which law enforcement itself intentionally shifted their own communications to this very same platform will be relevant evidence for the jury … particularly if a substantial amount of law enforcement material is in fact unpreserved.”