SIOUX FALLS, S.D. (AP) — The Latest on South Dakota's scheduled execution of Charles Russell Rhines in the 1992 slaying of his former co-worker (all times local):

9:50 a.m.

The South Dakota Supreme Court has rejected an appeal by a state prisoner scheduled to die by lethal injection Monday in the slaying of a former co-worker.

Charles Russell Rhines argued that the state's choice of drug to be used in his lethal injection does not meet the requirement of being "ultra-short-acting" that was in effect at the time of his conviction.

A circuit judge last week rejected his argument, writing that the pentobarbital South Dakota will use works as fast or faster as other drugs cited by Rhines when used in lethal doses.

The state's high court agreed.

Rhines immediately appealed that ruling to the U.S. Supreme Court, which already has an appeal by Rhines on other grounds.

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5:48 a.m.

A man who stabbed to death a former co-worker who interrupted him during a burglary is set to be executed in South Dakota barring a last-minute stay.

Charles Russell Rhines brushed off a plea for mercy from 22-year-old Donnivan Schaeffer in the 1992 slaying at a Rapid City doughnut shop.

Now 63, Rhines unsuccessfully challenged the execution drug the state plans to use in Monday's execution in Sioux Falls. He's appealing that ruling to the state Supreme Court.

Rhines has also asked the U.S. Supreme Court to block his execution. He argues that the jury that sentenced him to death had an anti-gay bias. He also argues that the state hasn't allowed him to be examined for cognitive and psychiatric impairments.