The results of an independent May 14 autopsy performed on Clayton Lockett’s remains ruled that his April 29 state-sponsored murder was mishandled by prison staff.

The report, released last Friday, June 13, established that the inmate suffered a heart attack after the execution team botched the procedure due to their inability to locate the proper veins.

“The improper placement of the IV used in Mr. Lockett’s execution is just one factor that caused his prolonged and painful death,” said Megan McCracken, an attorney with the Death Penalty Clinic at the University of California, Berkeley, School of Law. “The three-drug protocol that was used exacerbated the pain and suffering that Mr. Lockett faced by needlessly paralyzing him and subjecting him to the pain of potassium chloride. Moreover, the state had no plan for contingencies in the event that the execution did not go as planned, as clearly happened here.”

Reports say Lockett received a dose of midazolam, which causes unconsciousness, at 6:23 p.m. At 6:33 p.m., a doctor found him to be unresponsive, but three minutes later, the 38-year-old began mumbling, slightly moving and struggling to lift his head.

“The director did say that it appears that a vein [in Lockett’s body] blew up or exploded; it collapsed, and the drugs were not getting into the system like they were supposed to,” Oklahoma Department of Corrections spokesman Jerry Massie revealed.

Massie added that after the initial injection, the condemned man “was obviously showing some movement. After several minutes, five minutes, he was not unconscious. They made a decision to halt the execution, but at 7:06, he suffered a massive heart attack and died.”

Due to the complications, the other two drugs were never injected: vecuronium bromide, which stops respiration, and potassium chloride, which stops the heart.

Oklahoma Gov. Mary Fallin had strongly pushed for a double execution but ordered a two-week stay for Charles F. Warner, who was to be murdered behind Lockett that same Tuesday night.

Lockett was convicted of killing a woman in 1999, while Warner was convicted for the 1997 murder of his girlfriend’s baby daughter.

One of Lockett’s attorneys, Dean Sanderford, witnessed his execution from the same room as the reporters. “Lockett’s movements started as twitching and ended like a seizure,” he described. “What we saw was somebody coming back to consciousness. He died in pain.”

Warner’s attorney, Madeline Cohen, called Lockett’s execution “horrible and certainly something we hope and pray will never happen again.” She added, “Despite repeated requests by counsel, the state has refused again and again to provide information about the source, purity, testing and efficacy of the drugs to be used. It’s not even known whether the drugs were purchased legally.”

Dr. Joseph L. Cohen, who performed the autopsy, stated in the report that the team tried to insert the IV on both sides of Lockett’s groin, leaving “skin punctures on the extremities and right and left femoral areas, and essentially set an improperly placed IV into the femoral vein.”

The apparent suffering Lockett underwent has raised concerns amongst opponents of the death penalty about how properly trained the personnel were and has them calling for the abolition of the practice.