WICHITA, Kan. (AP) — A registered sex offender who sent obscene material while he was a patient at Larned State Hospital has been sentenced to 20 years in federal prison.

U.S. Attorney Barry Grissom announced that 34-year-old Christopher Case was sentenced Monday to transferring the material.

Prosecutors say Case used a cell phone to send an obscene video to a 13-year-old girl in Montana in January 2012. He was a patient of the state’s sexual treatment program at the time.