July 16 (Reuters) — The U.S. federal government on Thursday executed its second prisoner this week, following a 17-year pause after the U.S. Supreme Court again intervened to allow the execution to proceed, overturning a lower court ruling that had blocked it.

The Justice Department executed convicted murderer Wesley Purkey by lethal injection, and he was pronounced dead at 8:19 a.m. EDT at the federal prison in Terre Haute, Indiana, a Bureau of Prisons spokeswoman said.

The execution had been blocked by a federal court, but the Supreme Court overruled it, just as it did in another case on Tuesday, and putting the federal government back in the business of executing prisoners.

"This sanitized murder really does not serve no purpose whatsoever. Thank you," a remorseful Purkey said in his final words, according to a reporter who was allowed to witness the killing and share notes with the media.

Purkey, 68, was convicted in 2003 in Missouri of raping and murdering 16-year-old Jennifer Long before dumping her dismembered and burned remains in a septic pond.

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His lawyers argued he had dementia and brain damage caused by Alzheimer's disease and no longer understood his punishment, though he had accepted responsibility for his crime. Killing him would breach the U.S. Constitution, they said.

"I deeply regret the pain and suffering I caused to Jennifer's family. I am deeply sorry. I deeply regret the pain I caused to my daughter, who I love so very much," Purkey said after he was strapped to a gurney inside the execution chamber, his arms tied to side boards, and an intravenous syringe was inserted into his right arm.

Before Tuesday, when the Justice Department executed convicted killer Daniel Lee in Terre Haute, the federal government had only executed three people since 1963, all from 2001 to 2003.

(Reporting by Peter Szekely and Jonathan Allen in New York; Writing by Daniel Trotta; editing by Jonathan Oatis and Bernadette Baum)