Georgia is set to execute a death row prisoner this evening using a single dose of pentobarbital from a secret source. On Monday, a federal judge rejected Marcus Wellons’ argument that the secrecy violates his rights and could cause undue suffering. Unless a court issues a reprieve, Wellons will become the first prisoner executed in the United States since the botched execution in Oklahoma of Clayton Lockett, who writhed, groaned and took 43 minutes to die. Initial findings from an independent autopsy released last week found the execution team failed to properly place Lockett’s IV. Two other executions are planned for Wednesday in Florida and Missouri — two states that also conceal the sources of their lethal drugs.