ATMORE, Ala. (AP) — An Alabama execution in which a prisoner heaved his chest, coughed and appeared to move offers more evidence that a drug used to sedate inmates before they are put to death should not be used in lethal injections, critics of the drug said Friday.

Alabama prison officials insisted there was no reason to believe Robert Bert Smith Jr. suffered after receiving the first of three drugs.

The debate focuses on midazolam, a drug that has been used in executions that were called into question in several other states. It has been the subject of multiple legal challenges.

Smith was given the drug late Thursday to put him to sleep. His movements occurred moments later during tests to determine an inmate’s level of consciousness before administering two more drugs to stop the heart and lungs.

Smith’s legal team said the prisoner’s movement showed “he was not anesthetized at any point during the agonizingly long procedure.” As they awaited results of a required autopsy, the attorneys said “no autopsy can measure the extent of Ron Smith’s suffering as he died.”

The 45-year-old was convicted in the 1994 fatal shooting of a Huntsville store clerk named Casey Wilson. Smith coughed and heaved his chest repeatedly over a 13-minute period of the 30-minute execution process and appeared to move his arms slightly after the two tests.

In a statement issued Friday, Alabama Department of Corrections Commissioner Jeff Dunn acknowledged that Smith coughed with his eyes closed, but officials said there was no “observational evidence that he suffered.”

This was Alabama’s second execution using midazolam. The U.S. Supreme Court ruled 5-4 in a 2015 case from Oklahoma that condemned inmates had not proven that midazolam violated the Eighth Amendment prohibition on cruel and unusual punishment. Inmates have continued to challenge its use, saying it is a sedative, not an anesthetic, and cannot reliably render a person unconscious.

Oklahoma inmate Clayton Lockett in 2014 writhed on a gurney, moaned and clenched his teeth for several minutes before prison officials tried to halt the process. Lockett died after 43 minutes. A state investigation revealed that a failed intravenous line caused the drugs to be injected into his tissue, not directly into his bloodstream.

Ohio and Arizona have used midazolam as the first in a two-drug protocol. Ohio inmate Dennis McGuire repeatedly gasped and snorted for more than 26 minutes during his January 2014 execution.

Smith’s “reaction to the drug — the struggling, the gasping, the moving, the coughing — that’s consistent with the problematic executions we’ve seen in other states with this drug,” said Jen Moreno, a staff attorney with the Death Penalty Clinic at the University of California’s Berkeley Law School. She called it one more example of why states should not use midazolam.

The execution began about 10:25 p.m. when the warden read the death warrant and asked Smith if he had any last words. A few minutes later, the warden left the death chamber to administer the drugs from an adjacent control room that looks into the chamber.

It is unclear exactly when the midazolam began flowing. Smith clenched his fists and raised his head early in the procedure. His face turned red after he rested his head back on the gurney. The coughing and chest heaving followed.

During the execution, a corrections officer gave Smith the two consciousness checks, which involved stroking the area around his eyes, saying his name and pinching his left arm.

The first check was given at about 10:37 p.m. Smith’s left arm moved slightly following the pinch. A second check was performed 10 minutes later. Smith did not immediately respond but shortly afterward, his right hand and lower arm appeared to move slightly.

Smith’s breathing and coughing then slowed to where they were no longer visible. The curtains to the viewing room closed at 10:59 p.m. A prison system spokesman said a doctor pronounced Smith dead at 11:05 p.m.

“The execution confirms there are questions that need to be resolved before carrying out additional death sentences,” Bryan Stevenson, executive director of the Alabama-based Equal Justice Initiative.

For more than three decades, all death penalty states used the same three-drug combo for lethal injections. But then supplies of the drugs started to run short as death penalty opponents in Europe put pressure on drugmakers to prohibit their use in executions.

States also began to seek alternatives to avoid lawsuits alleging the old three-drug method caused inmates to suffer.