Updated

The scheduled execution of a two-time killer has been put on hold while an appeals court considers his petition that death by injection is unconstitutionally cruel.

In a brief three-paragraph order released Monday, the Texas Court of Criminal Appeals blocked the execution of Derrick Sean O'Brien, condemned for the 1993 killings of Jennifer Ertman, 14, and Elizabeth Pena, 16.

Lawyers for O'Brien, 31, contended in their appeal that the execution drugs used in Texas "unnecessarily create a risk that O'Brien will suffer excruciating excessive pain."

Death penalty critics have argued that the painkiller sodium pentothal could wear off, causing pain, before a second drug, pancuronium bromide, paralyzes the inmate. A final drug, potassium chloride, causes a fatal heart attack.

The U.S. Supreme Court heard arguments in a Florida case last month that questions whether inmates can file special last-minute civil rights challenges to the chemical cocktail used in lethal injection. The justices are expected to issue a decision before July.

The Texas drug procedure is similar to the one use in Florida, but until Monday's ruling, similar appeals in Texas death penalty cases had failed.

"The Court of Criminal Appeals has indicated, it appears, its willingness to temporarily defer executions until we have a better sense from the high court whether challenges of these types can be raised," said Catherine Greene Burnett, one of O'Brien's lawyers.

An indication of the ruling's impact could come quickly. Texas prison officials were scheduled to execute another inmate, Jermaine Herron, on Wednesday evening.

"We'll continue to address legal challenges presented in individual cases as they're brought through proper legal channels," said Jerry Strickland, a spokesman for Texas Attorney General Greg Abbott.

The Texas court ruling made little sense to Randy Ertman, whose daughter was one of the girls killed in the savage attack involving O'Brien and five companions.

"I don't have any respect for any politician," Ertman said of the court, whose members are elected. "They're a joke — a real joke."

Ertman had planned to witness O'Brien's execution at the death chamber Tuesday in Huntsville, where 363 inmates have received lethal injection since 1982, more than any other state.