The 68-year-old man was convicted in 2003 of raping and violently murdering 16-year-old Jennifer Long before throwing his dismembered and burned remains into a septic tank.
Long had skipped school in the morning of January 1998 when she was drawn into the van of Purkey, a stranger who was going crazy.
The brutal ex-crook had traveled to Kansas City from his Lansing home before spotting the shy brown tomboy walking near East High School.
Attracting her to his car with party promises, Purkey took Long to his basement where he raped her and stabbed her repeatedly when she tried to escape.
Then, using an electric chainsaw, he cut his body into pieces and burned them in his fireplace.
The execution was blocked by a federal court, but the United States Supreme Court overturned it today, as it did Tuesday in another case.
Purkey was pronounced dead at 8:19 a.m. EDT [12.19pm GMT] in the execution chamber of the Department of Justice at the Terre Haute federal prison, Indiana.
His lawyers had claimed that he suffered from brain damage and dementia caused by Alzheimer’s disease.
They said that although he accepted responsibility for his crime, he no longer understood the reason for his execution and that killing him would violate the United States Constitution.
Before Tuesday, when the Department of Justice executed the convicted murderer Daniel Lee in Terre Haute, the federal government had only executed three people since 1963, all from 2001 to 2003.
Lee joined Purkey and other death row inmates in lawsuits challenging the new government’s lethal injection protocol for a drug using pentobarbital, a barbiturate, announced by the Department of Justice a year ago .
He replaced it with the previous three drug protocol.
Federal judge agreed with medical expert cited by lawyers for convicted men that the drug was likely to violate a constitutional ban on “cruel and unusual punishment” by causing a painful drowning sensation as bloody fluid filled their lungs before to pass out.