RAPID CITY,S.D. (AP) — A death-row inmate in South Dakota is challenging the state’s single-drug execution protocol.

Charles Russell Rhines appeared in 7th Circuit Court on Tuesday to hear recorded testimony from health care experts about the one-drug method.

Rhines has been sentenced to death for the 1992 fatal stabbing of 22-year-old Donnivan Schaeffer during the burglary of a Rapid City doughnut shop. His conviction and death sentence was upheld in September, and now Rhines is challenging the constitutionality of the state’s one-drug protocol.

A judge will rule on the legality at a later date.

Rhines can appeal the decision to the South Dakota Supreme Court and the U.S. Supreme Court.