Allen entered a blind guilty plea to first-degree murder, meaning he had not reached a plea deal with prosecutors and did not know what the sentence would be. A judge sentenced him to die.
Allen's attorneys argued he was not competent enough to enter the plea. They also contended he was mentally impaired when he killed Titsworth, that he had been self-medicating for a mental illness and that his mental condition became worse on death row. The U.S. Constitution forbids the execution of inmates who are insane or mentally incompetent.
A judge halted Allen's original May 19, 2005, execution after a psychological examination at the prison indicated Allen had mental problems. Three years later, a jury rejected Allen's claims he should not be put to death.
The Oklahoma Pardon and Parole Board had voted in April 2005 to recommend that Allen's death sentence be commuted to life without parole. That clemency recommendation wasn't acted on until this year, when Republican Gov. Mary Fallin denied it.