In newly unsealed court filings, attorneys for the Gwinnett County Sheriff’s Office confirmed that a federal grand jury is conducting a criminal investigation into the agency’s “rapid response team” — and argued it was “highly unlikely that any criminal activity will be uncovered.”

The controversial RRT squad takes part in what the sheriff’s office describes as “high-risk tactical operations” inside the county jail.

“Counsel has become aware of a federal criminal investigation by the U.S. Attorney’s Office into the activities of the Rapid Response Team (also referred to as “RRT”) at the Gwinnett County Detention Center,” Thomas Mitchell, an attorney for the sheriff’s office, wrote in an Aug. 7 filing.

“Neither the U.S. Attorney nor the subpoena identify any particular RRT member or act that is the subject of the investigation. Rather it appears to be a broad investigation of the activities of the RRT, such that all members are at least potential subjects of the investigation.”

Mitchell's filing was made as part of an ongoing federal lawsuit filed in 2013 over the RRT's use of "restraint chairs," devices designed to hold unruly inmates' arms, legs, chest and head in place. The civil lawsuit — filed in U.S. District Court in Atlanta, initially on behalf of a dozen or so former Gwinnett inmates — alleges that the chairs amount to excessive force and were inappropriately used as punishment.

The suit, filed by attorneys John Cicala and Craig Jones, has taken several twists and turns during its journey through the judicial system. The latest came Friday, when U.S. District Judge Steve C. Jones denied the sheriff's office's request to delay proceedings.

Jones’ ruling resulted in several previous filings being unsealed and made public. And in those filings, the sheriff’s office itself confirmed for the first time the existence of the federal criminal investigation.

The sheriff’s office’s legal team also tried to use that investigation as the basis for halting proceedings in the lawsuit. It argued that the former would prevent subpoenaed officials from testifying in the latter.

The agency’s attorneys argued as well that the public shouldn’t know about the generally secretive grand jury proceedings.

“But for [the civil lawsuit], no investigation would be pending,” one filing said. “Even if an investigation had been initiated, the RRT members could have enjoyed the normal confidentiality typically afforded grand jury investigations. Defendants need to request the stay but the public need not be alerted through this case about the investigation, especially to the detriment of the reputation of the non-party RRT members.”

Jones, the judge, ruled against the sheriff’s office. He said, in part, that the public was already aware of the grand jury investigation through previous media reports.

The grand jury has subpoenaed several years worth of videos showing the actions of the rapid response team. Dozens of such videos — which show helmeted deputies storming into jail cells to restrain or subdue inmates, sometimes by using pepper spray or pepper balls — have been made public over the years, either through litigation or open records requests.

Gwinnett County Sheriff’s Office spokeswoman Deputy Shannon Volkodav declined to comment Monday on the ongoing litigation and on the federal grand jury. The potential time frame for the latter’s investigation was unclear.