BALTIMORE (AP) — Prosecutors said in opening statements that the highest-ranking officer charged in the death of a young black arrestee was criminally negligent when he failed to buckle him into a seat belt or direct other officers to ensure the man’s safety.

Baltimore Police Lt. Brian Rice faces manslaughter, assault and other charges stemming from the death of Freddie Gray, whose broken neck in the back of the police van last year sparked riots and upheaval.

Prosecutors told Baltimore Circuit Judge Barry Williams that Rice “wasn’t an inexperienced officer” and was well aware of his duty to belt Gray in to secure his safety.

Chief Deputy State’s Attorney Michael Schatzow said, “he knew he was obligated to ensure the safety of Mr. Gray. He knew it, and he ignored it.”