Convicted murderer executed in Missouri with the experimental chemical pentobarbital

A convicted murder was executed by lethal injection Wednesday night in the US state of Missouri, his lawyers said.

Herbert Smulls, 56, was put to death after a reprieve granted by US Supreme Court Judge Samuel Alito late Tuesday was lifted by the court.

Smulls had challenging the use of the drugs that were to be used to execute him.

After the reprieve was lifted, and before the man was executed, three other appeals were filed. The last was still pending when he was put to death, his legal team told AFP.

Smulls was on death row for the 1991 killing of a jeweler during an armed robbery. The governor of Missouri rejected his petition for a stay of execution.

The challenge he lodged was over the use of the chemical pentobarbital, manufactured by a compounding pharmacy whose identity has not been revealed.

Alito is the justice assigned to cases from the region of the United States that includes Missouri.

He is expected to rule soon on a similar petition from Louisiana inmate Christopher Sepulvado, due to be put to death next week.

Sepulvado is scheduled to die for fatally beating and scalding his six-year-old stepson in 1992.

Attorneys for both men maintain that the failure to reveal the identity of the pharmacy makes it impossible to know if the execution would constitute "cruel and inhumane punishment" under the Eighth Amendment of the US Constitution.

They suggested that the barbiturate used to put the inmates to death might have been tested and approved by the same lab that tested drugs used in a controversial recent execution in Oklahoma.

In that instance, Michael Lee Wilson, who was executed on January 9, said he could feel his whole body "burning" as he was put to death.

An expert cited by lawyers for Smulls said the same Oklahoma lab is believed to have approved drugs produced in Massachusetts allegedly responsible for an outbreak of meningitis in November 2012.

After the Missouri governor refused late Tuesday to stay the execution, lawyer Cheryl Pilate asked the Supreme Court to demand that the state divulge the name of the pharmacy that provided the drug it intends to use for the lethal injection.

Missouri, along with some other US states, faces a shortage of drugs previously used in lethal injections after European drugmakers refused to supply substances to be used in executions.

Like other states, Missouri has turned to so-called compounding pharmacies not subject to federal drug safety regulations to procure the drugs.