A federal grand jury has charged a deputy warden at Mississippi’s state penitentiary with injuring an inmate in 2016 and lying about it to investigators.

Prosecutors said Melvin Hilson was a member of the K-9 unit at the prison when the inmate was struck and repeatedly knocked to the ground.

The indictment said Hilson falsely claimed in a report that he had found some type of contraband on the inmate. It also accused Hilson of lying about the incident to Mississippi Department of Corrections investigators.

The indictment was dated June 24. Hilson has pleaded not guilty. Arraignment is set for Thursday, with an Aug. 23 trial date set. Hilson has not been ordered detained pending trial.

The Justice Department announced grand jury’s decision in a news release Tuesday from Washington by Assistant Attorney General Kristen Clarke for the Justice Department’s Civil Rights Division, Acting U.S. Attorney Clay Joyner for the Northern District of Mississippi and FBI Jackson Special Agent in Charge Michelle Sutphin.