Tomorrow, when the Supreme Court hears oral arguments in the highest-profile death penalty challenge in seven years, the justices will begin ruling on this question: Does Oklahoma’s use of the common surgical sedative midazolam fail to make prisoners unconscious during lethal injections, thus violating the Eighth Amendment’s protection against “cruel and unusual punishment”? For many court watchers, however, a subject of special scrutiny will be the credibility of Oklahoma’s key expert witness, Dr. Roswell Lee Evans, who has testified that inmates “would not sense the pain” of an execution after receiving a high dose of midazolam.

The case, first brought by four condemned Oklahoma inmates, stems from the botched April 2014 execution of convicted murderer Clayton Lockett. Although Lockett received a substantial dose of midazolam intravenously, it failed to render him unconscious as he was administered the paralytic agent vecuronium bromide and the caustic heart-stopping drug potassium chloride. Witnesses reported that he moaned and writhed on the gurney for more than 40 minutes until his death.

Lethal injections involving midazolam in other states have been similarly grisly. In Ohio, Dennis McGuire heaved and snorted during his 26-minute execution. Last July, Arizona took two hours to execute a man. After these deaths, Evans maintained that midazolam works.

Oklahoma and four other states began using the sedative in 2013 after the American pharmaceutical manufacturer Hospira halted production of the anesthetic sodium thiopental in the wake of increasing anti-death penalty sentiment. Since then, according to the Death Penalty Information Center, midazolam has been used in 15 executions, one-quarter of which were apparently painful.

A number of legal activists and medical professionals have expressed concern that Evans, a board certified psychiatric pharmacist and the dean of the Harrison School of Pharmacy at Auburn University in Alabama, has testified that he has never used midazolam on a patient and has, in fact, never personally induced anesthesia.

According to his curriculum vitae, which he submitted as part of his testimony, the last time Evans published a paper related to his pharmacology research was in 1996. Moreover, his 300-page expert witness report included more than 150 pages of printouts from drugs.com, an online consumer website whose disclaimer reads, “not intended for medical advice, diagnosis or treatment.”

Last month, 16 professors of pharmacology filed a brief with the Supreme Court that disputes Evans’ testimony. “It is widely recognized in the scientific and medical community that midazolam alone cannot be used to maintain adequate anesthesia,” the doctors asserted, describing how the drug’s potency does not increase with dosage – a so-called “ceiling effect.” They concluded that midazolam “is incapable of rendering an inmate unconscious prior to the injection of the second and third drugs.”

Dr. Kelly Standifer, one of the brief’s authors and chairwoman of the Department of Pharmaceutical Sciences at the University of Oklahoma College of Pharmacy, told ProPublica that she was “a little horrified” when she read Evans’ testimony. “My first impression was that it was wrong. These kinds of doses are not given by any clinician. To say that they would know what this dose would do? I don’t think anyone can say that.”

Dr. Richard Weisman, a toxicologist and an associate dean at the University of Miami Miller School of Medicine, said that since midazolam has never been tested on patients at high dosages, it would be impossible for Evans to deduce its efficacy. “It becomes a big experiment and that’s not good for something like this,” Weisman said.

But it’s Evans’ reliance on a consumer website that has attracted the most scrutiny from medical professionals. “As scientists we use primary literature – it’s a little different than drugs.com,” said Dr. Kathryn Cunningham, the vice chairwoman of the pharmacology and toxicology department at University of Texas Medical Branch and another of the brief’s authors. “As someone who is a scientist, we have resources available to use so we would not go to a website of this sort.”

Even Supreme Court Justice Sonia Sotomayor wrote earlier this year that she was “deeply troubled” by Evans’ research standards. “In contending that midazolam will work as the State intends, Dr. Evans cited no studies, but instead appeared to rely primarily on the Web site www.drugs.com,” Sotomayor noted in a dissenting opinion to stay the execution of Charles F. Warner, one of the original petitioners in the case. “It is true that we give deference to the district courts. But at some point, we must question their findings of fact, unless we are to abdicate our role of ensuring that no clear error has been committed. We should review such findings with added care when what is at issue is the risk of the needless infliction of severe pain.”

An hour later, Warner was executed after receiving a dose of midazolam. His last words were reportedly, “my body is on fire.”

Evans declined to be interviewed for this article. In his testimony before the federal court in Oklahoma last December, he defended his drugs.com research, describing the website as a “combination of materials pulled from some of the most outstanding references in the country that have been around for 50-plus years.”

Originally from Georgia, Evans received his Doctor of Pharmacy from the University of Tennessee, Memphis, in 1973. He was a professor at the University of Missouri-Kansas City for nearly 20 years before becoming a dean at Auburn University. He is licensed to practice pharmacy in two states—but is not licensed to practice pharmacy in Alabama, the state he has worked in for over 20 years. “It is telling that the states have selected an expert who does not use or study the drug in question and who based his opinions on unreliable sources,” said Megan McCracken, a legal expert at the Death Penalty Clinic at the University of California, Berkeley.

The nation’s judicial system has long emphasized the importance and need for reliable scientific testimony, often referred to as the “Daubert Standard.” Under this precedent, established in 1993, all courts have an obligation to ensure that scientific testimony is based on scientific knowledge.

“If you’re trying to figure out whether it’s cruel or unusual punishment, the inquiry into the chemical component needs to be more robust and thorough,” David Loftis, the managing attorney of the Innocence Project, said in an interview with ProPublica. “Just because he’s a scientist doesn’t mean he knows the properties of the drug."

The problem, Loftis says, is the speed in which death penalty challenges must often be heard. Dale Baich, an attorney representing the Oklahoma prisoners in the Supreme Court case, said this was exactly the situation with Evans, who testified only a month before Charles Warner’s execution date.

“Because the Oklahoma case went forward in an expedited manner, Dr. Evans was not fully challenged during the hearing as there was no time to take his deposition and conduct an in-depth investigation of his professional background and credentials,” Baich said in an interview.

Ultimately, though, what the intense battle over Evans’ qualifications reveals are the larger forces at work in the country’s ongoing capital punishment debate. “The choice of using a method of execution that is so dependent on the medical profession and pharmacology has bitten the Departments of Corrections in the back” said Deborah Denno, a death penalty expert and professor of law at Fordham University. “The Departments of Corrections are pretty desperate to find experts who can support their point of view. States have had a lot of trouble finding experts to come forward, and when they do come forward, they are not qualified.”

In recent years, the medical community has begun to speak out against capital punishment. The American Medical Association, the largest association of medical doctors, discourages its members from participating in executions. In 2010, the American Board of Anesthesiology even went so far as to threaten to rescind board certification of any of its 40,000 members if they chose to participate in an execution.

In recent weeks, both the American Pharmacists Association and the International Academy of Compounding Pharmacists have adopted positions discouraging their members from participating in executions.

A consequence of these shifts is that the pool of expert witnesses willing to defend lethal injection is drying up. Take the case of Dr. Mark Dershwitz, a professor of anesthesiology at the University of Massachusetts Medical School. Since at least the early 2000s, Dershwitz has provided expert testimony in more than 20 states on lethal injection drugs (including midazolam). But in June 2014, Dershwitz terminated his role as a state expert. He declined to be interviewed for this article, telling ProPublica in an email, “as requested by the American Board of Anesthesiology, I do not discuss lethal injection in any venue.”

That may be why states like Oklahoma are turning to doctors such as Roswell Lee Evans – and why his testimony is likely to come under special scrutiny in the Oklahoma case.