Compounding pharmacies, which create specialized pharmaceutical product meant to fit the needs of a patient, have begun producing the drugs for state authorities.

But because of the lack of transparency around the production process – one compounding pharmacy was responsible for a fatal meningitis outbreak in 2012 because of poor hygiene – prisoners argue that risky drug cocktails put them at risk of being subjected to “cruel and unusual punishment,” which is prohibited under the US Constitution.

Earlier this month three Texas-based death row prisoners filed a lawsuit arguing this type of pharmacy is “not subject to stringent FDA regulations” and is “one of the leading sources for counterfeit drugs entering the US,” the lawsuit reads, as quoted by AFP.

“There is a significant chance that [the pentobarbital] could be contaminated, creating a grave likelihood that the lethal injection process could be extremely painful, or harm or handicap plaintiffs without actually killing them,” it adds.

“Nobody really knows the quality of the drugs, because of the lack of oversight,” Denno told AFP.

Michael Yowell, who was convicted of murdering his parents 15 years ago, was executed in Texas Wednesday. He became the first inmate to be executed in Texas with pentobarbital since European nations halted production for this purpose. His lawyers unsuccessfully tried to stop him from being killed, saying the compounded factors in pentobarbital make the drug unpredictable and there have not been enough trials to guarantee the death is painless.

The states in question may find an applicable replacement for the short-term but, Denno argued, this development could be an indication that capital punishment is on the wane.

“How many times in this country can they change the way they execute?” she said. “There were more changes in lethal injections in the last 5 years than in the 25 preceding years.”