Austin, Texas (CNN) -- Relatives of a man executed in 2004 urged a Texas state commission Thursday to continue probing claims that outdated scientific testimony put him on death row as members weighed a legal opinion restricting their authority.
"You can't uninvestigate a case you've already investigated," Patricia Cox, the cousin of executed convict Cameron Todd Willingham, told the Texas Forensic Science Commission. "You can't unacknowledge what you've already acknowledged."
Willingham was put to death for setting a fire that killed his three daughters in 1991, but several experts who have reviewed the testimony in his trial say the fire was likely not arson. A series of studies in the 1990s rendered obsolete most of the things investigators pointed to as proof the fire was deliberately set, they say.
The commission's investigation was delayed after Gov. Rick Perry, now a Republican presidential candidate, replaced its chairman and three other members in 2009. The former chairman, Sam Bassett, now accuses Perry of trying to derail an investigation into Willingham's execution, which the governor allowed to go forward.
Perry has called Willingham a "monster" who was executed after every one of his appeals failed, a position his office restated after Bassett leveled his accusation in a CNN interview this week.
A July attorney general's opinion, requested by Bassett's replacement, appears to sharply restrict the commission's jurisdiction and may put an end to the Willingham probe. Members plan to discuss the matter in more detail Friday. But in light of the opinion, they voted Thursday afternoon to reject two complaints in which they had expressed concerns about evidence.
"Maybe we need a dismissal committee now," said commissioner Sarah Kerrigan, a toxicologist and college professor.
Commission members agreed to include letters highlighting their concerns with their official decision not to investigate the complaints.
The opinion concludes that the commission can only investigate cases in which evidence was tested after 2005 -- the year it was created -- and work done by state-accredited forensic laboratories since then. Commission member Lance Evans said the opinion is nonbinding, "but it does carry some weight."
"I think we have to consider it as a guideline," he said. He said the authors of the bill that created the commission never intended to limit it to post-2005 cases, but it would be up to the Legislature to change the law.
The Innocence Project brought the Willingham case to the commission on behalf of his family, and its policy director, Stephen Saloom, told the panel Thursday that the attorney general's opinion was mistaken.
"It was an incredible reach and a perversion of your role," Saloom said.
At a debate for GOP presidential candidates Wednesday night, Perry was asked whether he "struggled to sleep at night with the idea that any one of those might have been innocent."
Perry said, "I've never struggled with that at all," telling the audience that the state has "a very thoughtful, very clear process" of appeals. Meanwhile, the audience applauded when moderator Brian Williams pointed out that Perry had presided over 234 executions, more than any other governor in modern history.
