Correction: A typo in the original story has been corrected.

OKLAHOMA CITY (KFOR) – The plaintiffs in a trial challenging whether Oklahoma’s execution protocol is constitutional called their fifth witness to the stand during day two of testimony.

On Tuesday, attorneys for two dozen inmates who are challenging whether Oklahoma’s three-drug lethal injection cocktail is a humane way to execute people continued calling witnesses to the stand.

Dr. Mark Edgar, a pathologist who currently works as an autopsy director for the Mayo Clinic in Florida, continued his testimony.

Edgar talked about his review of 34 autopsies of death row inmates from all over the country. In each case, midazolam was the first drug used in the lethal injection cocktail.

According to Edgar, each of them suffered from “severe pulmonary edema,” which means their lungs were filled with bodily fluids. He said that can create a feeling of drowning or asphyxiation.

Dr. Edgar testified that this could be caused by the acidity of midazolam.

That list of inmates includes both Oklahoma death row inmates Bigler Stouffer and John Grant, who were executed in recent months.

During Grant’s execution, media witnesses said Grant vomited and convulsed after midazolam was administered.

After Dr. Edgar stepped down, attorneys for the inmates called Dr. James Williams to the stand. He’s a long-time firearms expert who also specializes in emergency medicine.

Williams shared some insight on using a firing squad as an alternative method of execution.

Eighteen of the 26 inmates who filed the lawsuit said they would prefer a firing squad over lethal injection.

“Execution by firing squad is feasible, practical and efficacious,” Williams said.

He testified that with a 30 caliber service rifle, and the target being the heart, the inmate is “almost immediately unconscious” within one to two seconds.

The plaintiffs will call their final witness, a doctor who witnessed Oklahoma’s most recent execution, to the stand Wednesday at 9 a.m.