An investigator working for the defense in Christie Michelle Scott's capital murder trial contends prosecution witnesses are mistaken when they call it an arson fire.

Prosecutors contend Scott, 30, started a fire at her Signore Drive home Aug. 16 to collect insurance from the death of her son in the pre-dawn blaze.

John Lentini, a private fire investigator from Georgia, testified Tuesday he could find no evidence the fire that killed 6-year-old Mason Scott was intentional. Lentini said he toured the burned home in September and again Monday.

"There's no credible evidence to support the fire was anything other than accidental," Lentini said while being questioned by lead defense attorney Robert Tuten, of Huntsville.

Lentini contends local, state and federal investigators who determined the fire started on or around a bed used by Mason Scott's younger brother, Noah, are incorrect. "There's no valid evidence to support the fire started on Noah's bed," he said.

The youths shared a bedroom. Noah Scott slept in his mother's bedroom the night of the fire. Christie Scott told investigators she awoke to discover the house was on fire and attempted to rescue Mason. After being turned back by intense heat and smoke, she and Noah escaped through a window in her bedroom.

Mason Scott's badly burned body was found on the floor beside his bed.

Lentini testified that high levels of carbon monoxide found in Mason's blood during an autopsy indicate the fire could not have started on a bed. Carbon monoxide, a byproduct of combustion, is a colorless, odorless gas that can be deadly. Lentini contends - as does fire protection engineer Douglas Carpenter who testified for the defense Monday - that Mason would have died of burns before inhaling massive of amounts of carbon monoxide if the fire had started on the bed.

Also like Carpenter, Lentini said the fire likely began in a television cabinet that was in the boys' bedroom. He and Carpenter testified the fire probably started inside the cabinet and smoldered for an extended period - producing copious amounts of carbon monoxide - before spreading to other furnishings in the room.

Lentini scoffed at contentions by prosecution fire experts who testified the blaze could not have begun in the television cabinet because books and papers in its base had little damage. Lentini said the books and papers did not burn because they were packed into the cabinet tightly and did not receive enough oxygen to ignite.

He was unable to determine how the fire started, but said it could have been ignited by the television.

Lentini told jurors that prosecution investigators ignored crucial evidence - such as the television cabinet - and focused their attention on Noah Scott's bed rather than combing the room for all possible sources for the fire. He accused the prosecution's fire experts of using investigative techniques that produce what he called unreliable results.

"There is no reason to believe the fire is anything but an accident," he said. "The methodology they used to determine this was a set fire is invalid."

During cross-examination by Franklin District Attorney Joey Rushing, Lentini said be believes prosecution investigators were mislead by a smoke detector found on the hall floor after the fire. Lentini contends investigators refused to believe the fire was accidental after the fallen smoke detector was found.

Prosecutors contend Christie Scott pulled the smoke detector from the wall before starting the fire to ensure its alarm would not wake up her son.

Lentini said Tuesday the smoke detector fell during the fire. He showed jurors a photograph that showed electrical wires for the smoke detector pointing toward the ceiling after the fire. He said if the smoke detector had been pulled from its mounting, the wires would have pointed toward the floor.

Prosecution witnesses have testified the smoke detector would have sustained heat damage if it had remained on the wall during the fire. Its mounting bracket, which remained on the wall, had heat and smoke damage.

During questioning by Rushing, Lentini said he is being paid $250 per hour by the defense for his investigative work and testimony. He expects to earn about $20,000 from working on the Scott case.

When Rushing asked Lentini why he frequently testifies for the defense in arson trials and has written magazine articles critical of fire investigators who work for government agencies, he replied, "I will tell you, fire investigation is in a sad state of affairs. It's getting better, but there's lots of mistakes being made by fire investigators."

Lentini bristled when Rushing asked if he was tainting his testimony to aid the defense. "What would you say to try to get Mrs. Scott off?" Tuten voiced an objection, which Franklin Circuit Court Judge Terry Dempsey sustained.

Dennis Sherer can be reached at 740-5746 or dennis.sherer@TimesDaily.com.