(FILES) This February, 29, 2000, file photo shows the execution chamber at the Texas Department of Criminal Justice Huntsville Unit in Huntsville, Texas, where convicted death row inmates are executed by lethal injection. The US Supreme Court on June 29, 2015 upheld the use of a controversial sedative in executions by lethal injection, saying it does not violate the Constitution. In a 5-4 ruling, the court's five conservative-leaning justices said that the plaintiffs -- death row inmates in Oklahoma -- failed to show that midazolam constituted a "substantial risk of severe pain." As a result, they said, the drug does not violate the Constitution's eighth amendment ban on cruel and unusual punishment. AFP PHOTO/Paul BUCK/FILES