Members of the state commission investigating a controversial Corsicana arson case in which three children died — and for which their father was executed — acknowledged on Friday that state and local arson investigators used "flawed science" in determining the blaze had been deliberately set.

But the Texas Forensic Science Commission panel heading the inquiry also found insufficient evidence to prove that state Deputy Fire Marshal Manuel Vasquez and Corsicana Assistant Fire Chief Douglas Fogg were negligent or guilty of misconduct in their arson work.

The investigators, they said, likely used standards accepted in Texas at the time of the fire, which erupted at the home of Cameron Todd Willingham in December 1991. Willingham went to his execution in 2004 proclaiming his innocence in the deaths of his 1-year-old twins and 2-year-old step daughter.

The tentative findings were announced at the commission's quarterly meeting in Houston.

Commissioners authorized the four-member committee to write a draft report reflecting their findings to be acted on later this summer. The panel, headed by commission Chairman John Bradley, also will solicit more information regarding the state of investigation standards in 1991. It will accept written public comments until Aug. 12.

Friday's action was the latest chapter in the contentious review of the arson investigators' work spurred by a complaint filed by the New York-based Innocence Project. The commission is not tasked with determining whether Texas might have executed an innocent man, but whether the arson investigators followed sound scientific principles.

Other reviews critical

At least three expert reviews, including a commission-financed study by Baltimore fire expert Craig Beyler, have been critical of the arson investigations. Burn patterns, multiple points of origin and other phenomenon investigators found at the scene wrongly were interpreted as signs the fire deliberately was set, the experts concluded.

Beyler, who wrote that investigators observed neither the standards of the National Fire Prevention Association, adopted shortly after the blaze, nor standards applicable at the time of the fire, was scheduled to appear before commissioners last September.

Days before the meeting, however, Gov. Rick Perry replaced the commission chairman with Bradley, district attorney in Williamson County. The session at which Beyler was scheduled to speak was canceled, and the fire expert never appeared before the body.

Friday's action spurred a heated exchange between Bradley and Innocence Project co-founder Barry Scheck, who bolted from his seat to protest. Bradley repeatedly refused to yield the floor.

Family optimistic

Scheck's organization argues that the state fire marshal's office should have been aware of updated arson investigation standards and - in any event - should have advised prosecutors and the court of them when they were adopted.

The new standards went into effect in early 1992.

"It's alarming that they've missed the point of our allegations," Innocence Project policy director Stephen Saloom said. "The state fire marshal's office had a continuing duty to inform prosecutors, the court, pardons and paroles or the governor of the unreliability of the old evidence."

While national fire experts may have known in late 1991 that new standards were in the works, investigation committee members said, it's possible rank-and-file investigators did not.

Willingham's mother, Eugenia Willingham, and his cousin, Patricia Cox, who were present for Friday's session, viewed the commission's action as a positive development.

"We're cautiously optimistic," Cox said. "We're Todd's voice after death. We're going to exonerate him. We're not going away."

Eugenia Willingham said her son would have been pleased. "His wish was that we clear his name," she said. "He was innocent and prosecuted for something he didn't do. ... I hope that somewhere or other he saw what happened today."

allan.turner@chron.com