GAINESVILLE, Fla. | For the first time in state history, Florida is expecting to execute a white man Thursday for killing a black person — and it plans to do so with the help of a drug that has never been used before in any U.S. execution.

Barring a stay, Mark Asay, 53, is scheduled to die by lethal injection after 6 p.m. Asay was convicted by a jury of two racially motivated, premeditated murders in Jacksonville in 1987.

The planned execution — Florida’s first since the U.S. Supreme Court halted the practice in the state more than 18 months ago — is expected to be carried out using etomidate, an anesthetic approved by the Florida Supreme Court. Two other drugs also will be used.

Asay, who is white, fatally shot Robert Lee Booker, 34, a black man, after making multiple racist comments, prosecutors said. Asay’s second victim was Robert McDowell, 26, who was mixed race (white and Hispanic). Prosecutors say Asay had hired McDowell, who was dressed as a woman, for sex and shot him six times after discovering his gender.

While Asay would be the state’s first white man to be executed in Florida for killing a black man, at least 20 black men have been executed for killing white victims since the state reinstated the death penalty in 1976, according to data from the Death Penalty Information Center. A total of 92 Florida inmates have been executed in that time period.

Opponents of capital punishment said much more needs to be done to make Florida’s criminal justice system more equitable.

"This does nothing to change the 170-year-long history of Florida not executing whites for killing blacks," said Mark Elliott, executive director of Floridians for Alternatives to the Death Penalty.

Etomidate is the first of three drugs administered in Florida’s new execution cocktail. It is replacing midazolam, which has been harder to acquire after many drug companies began refusing to provide it for executions. The etomidate is followed by rocuronium bromide, a paralytic, and finally, potassium acetate, which stops the heart. It is Florida’s first time using potassium acetate, too, which was used in a 2015 execution in Oklahoma by mistake, but has not been used elsewhere, a death penalty expert said.

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While the state’s high court has approved the use of etomidate, some experts have criticized the drug as being unproven.

"It’s never been used in an execution before," said Jen Moreno, a lethal injection expert who works as a staff attorney at the University of California, Berkeley Law School’s death penalty clinic. "There are outstanding questions about whether it’s going to do what it needs to do during an execution. The state hasn’t provided any information about why it has selected this drug."

State corrections officials defended the choice, saying it has been reviewed. The corrections department refused to answer questions from The Associated Press about how it chose etomidate.

"The Florida Department of Corrections follows the law and carries out the sentence of the court," Michelle Glady, the Florida Department of Corrections’ spokeswoman, said in a statement. "This is the department’s most solemn duty and the foremost objective with the lethal injection procedure is a humane and dignified process."

Doctors hired by Asay’s attorneys raised questions about etomidate in court declarations, saying there are cases where it had caused pain along with involuntary writhing in patients.

But in its opinion allowing the drug to be used, the state’s high court said earlier this month that four expert witnesses demonstrated Asay "is at small risk of mild to moderate pain."

Asay would be the first Florida inmate executed since a U.S. Supreme Court ruling found the state’s method of sentencing people to death to be unconstitutional. The court ruled that the old system was illegal because it gave judges, not juries, the power to decide.

Since then, Florida’s Legislature passed a law requiring a unanimous jury for death penalty recommendations.

In Asay’s case, jurors recommended death for both murder counts by 9-3 votes. Even though the new law requires unanimity, Florida’s high court ruled the U.S. Supreme Court’s ruling did not apply to older cases.

Asay will be the 24th inmate executed since Gov. Rick Scott has taken office, the most under any governor in Florida history.

Booker’s son, Vittorio Robinson, who was 15 when his father was killed, told the Florida Times-Union newspaper in Jacksonville his father’s death helped him realize that racism was still alive.

"I just couldn’t believe it," he said, describing when he learned of his father’s death. "And then it dawned on me there are actually still people out there that thought that way."