Houston (AFP) - The US state of Texas is pushing ahead with the use of lethal injection for its Death Row inmates despite legal challenges over the drugs it employs, in the latest chapter of a fraught national debate over how to conduct executions.

Texas is among the 27 states -- more than half the total 50 -- that has capital punishment on the books for certain violent crimes such as murder, drug trafficking and rape.

The Lone Star State has carried out executions for a century, and was the first to use lethal injection in 1982. 

Last year, two inmates filed parallel challenges to their pending executions, alleging that long-expired drugs would be used to kill them, possibly causing kidney failure and undue suffering.

Wesley Ruiz and John Balentine did not challenge their murder convictions. Ruiz was given the death sentence for the killing of a police officer in 2007 while Balentine was sentenced to die for killing his girlfriend's brother and his two friends in 1998. 

Instead, their lawyers argued that the possibility of suffering during an execution violated the constitutional ban against "cruel and unusual punishment."

The lawyers petitioned to prohibit the use of "expired drugs" by the Texas Department of Criminal Justice (TDCJ), claiming the pentobarbital to be used was "unlawfully obtained and long-expired."

"The pentobarbital respondents intend to use to execute (the two men)...  will act unpredictably, obstruct IV lines during the execution, and cause unnecessary pain," their petition said.

Texas prison authorities rejected the assertions, saying in a statement sent to AFP: "All lethal injection drugs are within their use dates and have been appropriately tested."

Initially their executions were stayed by a lower court, but that was overturned on appeal.

Ruiz was put to death on February 1. Balentine died by the same method a week later.

But the issue they raised is still percolating in the courts.

Five more people in Texas are due to be executed this year. Lawyers for some of them will pursue the lawsuit, and the next hearing is March 20.

'Compounded' drugs at issue

Only some states that mandate lethal injection employ pentobarbital. Ohio and Alabama use a three-drug cocktail built around the sedative midazolam, but those protocols have also been called into question in recent years. 

Some commercial laboratories banned the sale of their drugs for use in executions years ago.

Lawyers for Ruiz and Balentine allege that for nearly a decade, Texas has been buying "compounded" pentobarbital that expires more quickly than other commercially produced versions.

In 2016, the state's then attorney general Greg Abbott -- who is now the governor -- ordered that the names of the suppliers be withheld to avoid retaliation.

Michaela Almgren, a pharmacy professor at the University of South Carolina asked to provide an expert opinion by those attorneys, explained that a "compounded" drug has at most a 45-day use date limit if frozen.

According to state records reviewed by Almgren, the last purchase through the end of 2022 was made in March 2021 -- meaning those doses would have expired more than 600 days ago.

Another batch from 2019 would be more than 1,300 days out of date.

Yet those doses have been reassigned new use-by dates around September and November 2023, they complained.

'Violation of state law'

For Shawn Nolan, who represented both Ruiz and Balentine, "it is alarming that Texas continues to carry out executions with expired compounded pentobarbital, in violation of its own state law."

The compounded drugs "have limited useful lives, and expired compounded drugs are unreliable and unpredictable, increasing the risk of pain and suffering in the execution process," Nolan said.

Botched executions, while rare, do occur, mostly involving lethal injection. 

The nonprofit Death Penalty Information Center tallied seven botched executions last year, three in Alabama, three in Arizona and one in Texas.

Texas has carried out more than five times the number of executions than any other state over the last 47 years, according to data compiled by the center.