Washington, June 30 (RHC)-- The U.S. Supreme Court has ruled that the use of a controversial execution drug is constitutional when administering the death penalty.

In a 5-4 decision, the highest federal court of the United States on Monday refused to limit states' use of the sedative midazolam that opponents say has the effect of being burned alive. The drug had played a part in three long and painful executions last year in Oklahoma, Ohio and Arizona.

The court's conservative majority said lethal injection remains the most humane method of execution. U.S. Justice Sonia Sotomayor wrote a dissent for the four more liberal justices, arguing that the ruling "leaves petitioners exposed to what may well be the chemical equivalent of being burned at the stake."

Justice Stephen Breyer went further in a separate dissent. He said the high court should consider whether the death penalty violates the Constitution. Justice Ruth Bader Ginsburg agreed.

The lawsuit in Glossip v. Gross was brought by a group of death-row inmates in Oklahoma, who said the drug did not reliably induce unconsciousness and so violated the Eighth Amendment's ban on cruel and unusual punishment. Lower courts disagreed.

Oklahoma and several other states started to use midazolam in executions after drug companies in the United States and Europe refused to sell them the barbiturates that were traditionally used to produce unconsciousness.

According to the American Civil Liberties Union (ACLU), the racial ratio of the victims of the death penalty in the US has been striking since the revival of the practice in 1976, with the penalty being disproportionately imposed on Blacks and ethnic minorities.