AKIPRESS.COM - Missouri officials on Wednesday executed a man who had been convicted in 1993 of murdering a farming couple in their 60s in a plot to steal their cattle, a state official said.

William Rousan, 57, was pronounced dead at 12:10 a.m. (4.10 a.m. EDT) at a state prison in Bonne Terre, said Mike O'Connell, a spokesman for the state's Department of Public Safety, Reuters reported.

Rousan was convicted in the murders of 62-year-old Grace Lewis and her 67-year-old husband, Charles Lewis.

The U.S. Supreme Court on Tuesday refused to stay his execution. Rousan's attorneys had argued that Missouri's secrecy around its lethal injection drugs could result in undue suffering for the inmate as he was put to death.

After the court denial, Missouri Governor Jay Nixon denied a clemency request, clearing the way for Rousan's execution.

Controversy has arisen over lethal injection drugs as many states have turned to lightly regulated compounding pharmacies for supplies after the makers of drugs traditionally used in lethal injections largely stopped supplying them for executions.

Advocates for death row inmates say the convicts have a right to know the legitimacy of the supplier and details about the purity and potency of the drugs.

And they say the compounded drugs, which are not approved by the U.S. Food and Drug Administration, could lead to undue suffering that amounts to cruel and unusual punishment in violation of the U.S. Constitution.

In their petition to the U.S. Supreme Court, Rousan's attorneys had said the state was planning to use "compounded pentobarbital prepared by an unknown person in an unknown manner, without any assurance by an accredited laboratory that the substance is what the state purports it to be."