The Tennessee Supreme Court has refused to stay Thursday's scheduled execution of a convicted child killer while the state's new lethal injection protocol continues to be challenged on appeal.

The order brings Tennessee within days of killing Billy Ray Irick with a three-drug mixture, barring some last-minute change. Irick, 59, would be the first inmate Tennessee has executed since 2009. He was convicted of the 1985 rape and killing of a 7-year-old Knoxville girl.

Federal public defender Kelley Henry said she will request a stay with the U.S. Supreme Court. She had asked Gov. Bill Haslam to issue a temporary reprieve while the drugs are studied further. But the governor quickly ruled it out, saying he would not intervene.

"My role is not to be the 13th juror or the judge or to impose my personal views, but to carefully review the judicial process to make sure it was full and fair," Haslam said in a statement Monday. "Because of the extremely thorough judicial review of all of the evidence and arguments at every stage in this case, clemency is not appropriate."

The Tennessee Supreme Court's majority wrote that its rules require proving that the lawsuit challenging the lethal injection drugs is likely to succeed on appeal, but Irick's attorney has failed to do so.

In a ruling late last month, Davidson County Chancellor Ellen Hobbs Lyle wrote that attorneys for 33 death row inmates, including Irick, didn't prove that there is a substantially less painful means to carry out the execution or that the drugs the state plans to use would cause the inmate to be tortured to death.