Convicted killer Michael Taylor is shown in this Missouri Department of Corrections photo released on February 25, 2014. (via Reuters)

Missouri is scheduled to execute Michael Taylor on Wednesday at 12:01 a.m.

Taylor and Roderick Nunley were convicted in the 1989 kidnapping, rape and murder of a 15-year-old Ann Harrison. (Nunley remains on Missouri’s death row.)

The execution would be the ninth in the United States so far this year. Taylor, who was nearly executed in 2006 before a court-ordered stay, would be the second person executed in Missouri over that span, following the execution of Herbert Smulls on Jan. 29, according to the Death Penalty Information Center. (While the U.S. Supreme Court had briefly granted Smulls a stay shortly before the execution, the court denied last-minute appeals — including a final denial that came in about 30 minutes after Smulls had already died.)

Lethal injection is the primary method of execution in the United States, but in recent years, states have scrambled as they faced drug shortages. Missouri had planned to execute someone last fall using only the anesthetic propofal, which would have been a first in the country, but Gov. Jay Nixon (D) halted the execution following threats from the European Union to curb exports of the drug.

The Missouri Department of Corrections announced last fall that it had adopted a one-drug protocol using pentobarbital for its lethal injections. (Smulls was killed with an injection of pentobarbital last month.)

Taylor’s execution is set to come not long after an Oklahoma compounding pharmacy refused to give Missouri the drug needed for his execution. But last week, the state said in a filing that it had found a new supplier of its execution drug, though it didn’t reveal the supplier or the drug.

The department did not respond to a phone message on Tuesday.

Defense attorneys have been fighting to halt Taylor’s execution, owing in part to the state’s secrecy over the drug it will use. An appeals court earlier Tuesday denied several requests to stay the execution.

Lethal injections are drawing increasing attention due to the drug shortage and because of high-profile cases like Ohio’s execution of Dennis McGuire. It took nearly 25 minutes for McGuire to die, a period that saw him struggle, gasp and choke.

That execution “broke through” and drew additional media attention, said Richard C. Dieter, executive director of the Death Penalty Information Center, though he noted that most executions don’t go that way.

Still, the fact remains that states are experimenting with their executions by trying different combinations of drugs, Dieter said. The first four executions of the year — in Florida, Oklahoma, Ohio and Texas — used four different combinations of drugs.

“There’s not a settled way to carry out executions,” he said.