A federal appeals court ruled Wednesday that Oklahoma's infamous botched execution of convicted murderer Clayton Lockett two years ago did not amount to "cruel" or "inhumane" punishment. The three-judge panel of the 10th U.S. Circuit Court of Appeals in Denver voted unanimously that the lethal injection, though administered badly, was an unintentional and isolated incident.

The vote meant that Oklahoma prison officials did not violate the Eighth Amendment, which prohibits "cruel and unusual punishment."

"Some risk of pain is inherent in any method of execution -- no matter how humane," the appellate court reportedly reasoned in its ruling.

Lockett, an Oklahoma death row inmate, died of a heart attack on April 29, 2014, minutes after a doctor halted his execution after the procedure went awry. The first of three drugs, midazolam, was administered into his body via the femoral artery, but instead of pumping through his veins and leading to a quick death, the drug leaked into his body tissue.

The incident raised questions about the new lethal injection cocktails, which are seen as causing undue suffering while violating constitutional protections against unusual and cruel punishments.

A lawsuit was filed by Lockett's relatives claiming that Oklahoma's prisons department and a physician executioner were responsible for botching up the 38-year-old inmate's death. Lockett's estate claims in the lawsuit that the state violated the prisoner's rights by "experimenting" with an untested three-drug combination of midazolam, vecuronium bromide and potassium chloride.

Lockett was executed for the brutal 1999 murder of Oklahoma woman Stephanie Neiman.