(Updates with Supreme Court denying inmate's 11th-hour bid for a stay)
By David Beasley
ATLANTA, June 17 (Reuters) - The U.S. Supreme Court denied on Tuesday an 11th-hour request to block the execution of a Georgia inmate who was scheduled to be put to death Tuesday night in what would be the nation's first execution since a botched lethal injection in Oklahoma in April.
Marcus Wellons, 58, sentenced to die for the 1989 rape and strangulation of a teenage girl, also would become the first inmate executed in Georgia since the state Supreme Court upheld a new law in May shielding the identity and methods of compounding pharmacies that formulate lethal injection drugs.
Two more inmates were scheduled for execution on Wednesday, one each in Missouri and Florida.
But Wellons was slated to be the first since condemned Oklahoma killer and rapist Clayton Lockett died in April, suffering an apparent heart attack about 30 minutes after prison officials had halted his execution because of problems in administering the lethal injection.
The case ignited renewed debate and scrutiny of capital punishment in the United States, and even the White House criticized the botched execution as failing to adhere to humane standards.
A preliminary autopsy released by Lockett's lawyers last week showed the state failed to properly insert an intravenous line to deliver lethal drugs to Lockett.
Richard Dieter, executive director of the non-profit Death Penalty Information Center, said the Georgia execution of Wellons would be closely watched amid lingering questions about what went wrong during Lockett's death in Oklahoma.
"We're in a new climate," he said. "Everyone - the federal government, the president - is watching."
Wellons was convicted of killing his 15-year-old neighbor, India Roberts, whom he abducted as she walked to a school bus stop.
In his appeal to the Supreme Court, Wellons' attorneys cited the Oklahoma case to bolster their argument that Georgia had not provided enough detail about the state's execution protocol.
On Monday, the Georgia Board of Pardons and Paroles turned down the inmate's request for clemency. Wellons would be the 21st person executed in the United States this year, Dieter said. (Reporting by David Beasley; Additional reporting by Carey Gillam in Missouri; Editing by Colleen Jenkins; Steve Gorman and Michael Perry)