The U.S. Supreme Court on Wednesday added another wrinkle to Ohio's debate over how strictly the state's lethal injection procedures should be followed.

The court without comment refused to allow the execution of a condemned killer of an elderly couple to proceed, an execution delayed by federal courts over concerns that the state continues to deviate too often from its written rules for lethal injection.

Both the state and the inmate's attorneys were trying Wednesday to determine what comes next, but the decision is likely to further delay executions even though Ohio's procedures have never been ruled unconstitutional.

The court denied the state's appeal of decisions in inmate Charles Lorraine's case that said Ohio had strayed too far from its execution policies to be trusted to carry out the death sentence for now.

Federal courts must monitor every Ohio execution "because the State cannot be trusted to fulfill its otherwise lawful duty to execute inmates sentenced to death," the 6th U.S. Circuit Court of Appeals ruled last month.

The court upheld an earlier decision by U.S. District Court Judge Gregory Frost that chided Ohio for not following his warnings to adhere strictly to their policies.