(CNN) -- A team in Oklahoma that prepared condemned murderer Clayton Lockett for execution in April failed to set a properly functioning I-V in his leg, according to preliminary findings of an independent autopsy released on Friday.
The review was conducted by forensic pathologist Dr. Joseph Cohen in May and funded by Lockett's lawyers.
Lockett's attempted execution occurred at the Oklahoma State Penitentiary in McAlester. He died from an apparent heart attack 43 minutes after the execution began.
The autopsy was conducted separately from a formal state investigation. Outside examinations are common in certain cases.