Russell Bucklew, pictured in a February 2014 file photo provided by the Missouri Department of Corrections. (AP)

Russell Bucklew, pictured in a February 2014 file photo provided by the Missouri Department of Corrections. (AP)

Shortly after the clock reads midnight and Wednesday begins, Missouri plans to carry out its fifth execution of the year.

The state is scheduled to execute Russell Becklew, a convicted killer, at 12:01 a.m. Wednesday. If the execution occurs as planned, it will be the 21st in the country so far this year — and the first since a botched lethal injection in Oklahoma last month.

In 1996, Bucklew shot and killed a man before beating, raping and abducting an ex-girlfriend. He was arrested after a gunfight with police and, after escaping two weeks later, captured again, according to the St. Louis Post-Dispatch.

Bucklew's attorneys have asked courts to stay the execution, owing to a medical condition Bucklew has, as well as secrecy surrounding the state's lethal injection drugs. His attorneys say that Bucklew has a condition that causes weak blood vessels to grow in his face, head, neck and throat, causing bleeding from his face and mouth and pain. And they say that he has tumors in his head and neck that are partially blocking his airway. The attorneys cite medical experts in saying that Bucklew's condition will increase the odds that he will suffer during the execution.

"This rare and congenital medical condition increases the significant likelihood that the lethal injection drugs will not circulate properly in Mr. Bucklew's body and that he will hemorrhage and choke or suffocate to death due to his blocked airway," Cheryl Pilate, an attorney for Bucklew, said in a statement.

The U.S. District Court for the Western District of Missouri denied the request for a stay on Monday afternoon. Bucklew's attorneys filed an appeal with the U.S. Supreme Court on Tuesday and filed a separate motion asking the U.S. Court of Appeals for the Eighth Circuit for a stay.

"I'm sick about it not working on me. I'm afraid that it's going to turn me into a vegetable, that I'd be brain dead," Bucklew told the Guardian earlier this month. "You saw what happened down in Oklahoma. I'm the next guy up – am I gonna get all screwed up here? Are they gonna screw it up?"

Missouri Gov. Jay Nixon (D) has said he won't halt the execution.

Bucklew's attorneys also filed a motion last week asking that his execution be videotaped due to his medical condition, saying that they want to preserve evidence for a civil rights lawsuit showing that the execution will constitute cruel and unusual punishment.

Texas had been scheduled to carry out an execution last week, but that execution was halted at the last minute by a federal appeals court. The court halted it due to the inmate's intellectual disability after appeals from his attorneys; separately, his lawyers had also filed an appeal referencing the secrecy surrounding the drugs that would have been used.

Missouri, like Texas, executes inmates using a lethal injection of the drug pentobarbital. (This one-drug protocol differs from Oklahoma, which uses a three-drug protocol.) The state, which switched to using pentobarbital last year, executed Michael Taylor in February; this execution occurred despite a series of appeals as well as uncertainty over the drug that would be used in the injection. A compounding pharmacy in Oklahoma refused to provide the drugs, so the state found a new supplier that it did not identify.

This secrecy is the subject of a lawsuit filed last week by several news organizations. The Associated Press, the Guardian and three other media organizations sued the Missouri Department of Corrections to try and force the state to reveal where it is obtaining the drugs for lethal injections.

States have struggled in recent years to get the drugs necessary for lethal injections, causing several to experiment with new protocols and add a layer of secrecy to the process. The news outlets argued that the public had a right to know "the composition, concentration, quality, and source of drugs used in lethal injection executions."

Bucklew's scheduled execution and this lawsuit both arrive at a moment of heightened scrutiny for executions in the United States. The botched execution in Oklahoma of Clayton Lockett – a convicted murderer who writhed and grimaced before ultimately dying of a heart attack after the execution was called off – drew worldwide attention, including critical comments from President Obama and the United Nations.

In the lawsuit, the media outlets specifically mention this execution, which was witnessed by reporters from the Associated Press and the Guardian, saying that the bungled execution shows the how necessary it is to reveal information about the drugs used. The suit goes on to say that knowing details about the methods of execution "promotes public confidence in the integrity of the criminal justice system."

So far this year, Missouri has put four inmates to death, trailing Florida (which has killed five inmates) and Texas (which has killed seven inmates). That is as many executions as the state carried out between 2006 and 2013. The 20 executions so far this year have all occurred in five states: Florida, Oklahoma, Ohio, Texas or Missouri.

While the death penalty is still supported by a majority of Americans, that number has plummeted over the past two decades.

• Everything you need to know about the death penalty in the United States.

What it was like watching the botched Oklahoma execution.

• Creator of lethal injection protocol: "I don't see anything that is more humane."

See the evolution of the death penalty across the country.