JEFFERSON CITY, Mo. (AP) — An attorney for a man sentenced to 25 years in prison for rape is arguing that a Missouri law allowing sexually violent predators to be indefinitely committed to mental institutions is unconstitutional.

The Missouri Supreme Court heard arguments Thursday from attorneys for Jay Nelson and the state.

Nelson was convicted of rape in 1989. While in prison, he was accused of sexually assaulting female guards.

The state subsequently classified Nelson as a sexually violent predator. He has since been committed to the department of mental health until doctors determine he is safe for release.

Nelson’s attorney argues that the requirements for release, as set out in the statute, are impossible to meet. The attorney also says conditions in the facility are too restrictive for mentally ill patients.