The state made preparations on Wednesday to use a never-tried lethal drug combination to put a man to death for the slaying of a pregnant woman that went unsolved until he inadvertently helped authorities, and the U.S. Supreme Court refused to block the execution.

Dennis McGuire, jailed on an unrelated assault charge, told investigators he had information about the woman's Feb. 12, 1989, death. His attempts to blame the crime on his brother-in-law quickly unraveled, and soon he was accused of being Joy Stewart's killer, prosecutors said. More than a decade later, DNA evidence confirmed McGuire's guilt, and he acknowledged that he was responsible in a letter to Gov. John Kasich last month.

The state planned to execute McGuire on Thursday with a new process adopted after supplies of its previous drug dried up when the manufacturer put it off limits for capital punishment. The two-drug combination has never been used in a U.S. execution.

The state opposed McGuire's last-minute appeal, in which he claimed a jury never heard the full extent of his chaotic and abusive childhood.