As a rookie arson investigator in Marietta, Georgia, John Lentini never questioned his training. He once believed the old saw that the spalling of concrete, in which the surface chipped after a blaze, resulted from the kind of high heat indicating use of a liquid accelerant and arson. Likewise, he thought that only intentional use of a flammable liquid could explain walls with burn marks resembling a sharp-angled V or the charring of a floor.
That was before Lentini was called to work on a case in Jacksonville, Florida. In 1990 prosecutors charged Gerald Wayne Lewis with setting a house fire that killed his pregnant wife, her sister, and her sister’s four children. The fire showed all the classic signs of arson, including “pour patterns” on the floor: demarcation lines between burned and unburned areas that suggested a flammable liquid had been poured and ignited. But the suspect, who claimed his innocence, said he had no idea how the fire started.
Given the extensive publicity the case attracted and the fact that the murder charge carried a possible death penalty, prosecutors hired Lentini and John DeHaan, coauthor of a standard fire investigation text, to double-check and rule out other possibilities—including the hypothesis that one of the kids, playing with matches, had started the fire on a couch. As it happened, two doors down from Lewis’s house stood a nearly identical structure slated for demolition. Lentini and DeHaan got permission and funds to furnish the house with the same kind of carpeting and furniture as Lewis’s and wire the place with sensors. Then they lit the couch and got out.
Within minutes the living room had burst into flames, followed quickly by the entire house. The blaze went up much faster than investigators imagined was possible without an accelerant. Clearly flashover had occurred. After the fire Lentini and DeHaan found the same patterns on the floor that prosecutors had thought indicated arson in Lewis’s house. But rather than being produced by a liquid, the markings had been burned into the floor by the radiant heat released during flashover. The experiment, which became known as the Lime Street Fire [pdf], stunned everyone, and prosecutors dropped the charges. “That case opened my eyes,” Lentini recalls. “I was ready to send
Lewis to the electric chair.”
The following year Lentini had another conversion experience in a fire that became known as the Oakland Black Hole. A brush fire swept into that California city, killing more than two dozen people and destroying more than 3,000 homes. Eager to study fire in its natural habitat, Lentini and a crew of investigators moved in, examining 50 houses for postfire patterns. They knew the fire had been accidental, yet they found classic signs of arson: large, shiny blisters on wood resembling alligator skin, chipping concrete, and melted metal doorway thresholds, all typically attributed to accelerant and accelerant runoff, resulting in excessively high heat.
Lentini was particularly struck by the presence of tiny cracks, or crazing, in the window glass in a dozen houses around the periphery, where the firemen had been able to reach with their hoses. Crazing was commonly thought to indicate rapid heating and therefore, once again, the use of a fire accelerant. Back at the lab Lentini tested the idea, taking a dozen samples of window glass and heating them to 1400 degrees Fahrenheit in various ways—rapidly, slowly, some in an oven, some in an open flame. None of the samples exhibited crazing, but they all cracked when he sprayed them with cool water. Rapid heating did not cause the crazed pattern, he determined; rapid cooling did. In other words, one of the classic indicators of arson—one that had been used countless times in court to send suspects to prison—was probably caused by firemen spraying water on hot windows.
Lentini became a science convert, but most of his contemporaries did not. Year after year, poorly trained police or fire department officials contributed to faulty convictions. The most notorious such case reached a tragic conclusion in 2004, when the state of Texas executed a man for a fire that almost certainly was accidental. In 1991 Cameron Todd Willingham was accused of setting fire to a house and killing his three daughters. The prosecution relied on all the usual arson indicators: crazed glass, charred wood at the floor level, a melted aluminum threshold, and pour patterns of a flammable liquid. Witnesses had reported flames exploding out the windows—the main indicator of a flashover fire. Scientists and some field investigators, such as Lentini, knew that flashover fires could char wood at the floor level, melt metal, and create burn patterns that might suggest poured flammable liquid. Yet that information had not reached or convinced the state’s deputy fire marshal, Manuel Vasquez (who died in 1994). In 1992 Willingham was found guilty of murder and sentenced to death.
Years went by, and Willingham lost one appeal after another. Finally, in 2004, just weeks before Willingham’s scheduled execution, Gerald Hurst, an internationally known fire and explosives expert from Texas, was brought in to support a petition for clemency.
After reviewing the evidence and videotapes of the fire scene, Hurst wrote a report debunking the Vasquez findings, calling them “invalid in light of current knowledge.” Hurst said the blaze was almost certainly accidental, perhaps caused by a faulty space heater or electrical connection. But even that would be difficult to prove, because the house had been shoveled out by investigators. The cause of the fire should have been labeled “undetermined,” Hurst said, because there was no evidence a crime had actually been committed.
The Texas Board of Pardons and Paroles disagreed and denied the petition. After Willingham was executed, the Innocence Project, a national nonprofit legal organization focused on overturning wrongful convictions, assembled a team of leading arson investigators, who concluded that none of the evidence for arson in the case was scientifically valid. The project’s lawyers later filed an allegation with the newly formed Texas Forensic Science Commission alleging professional misconduct by the fire marshal’s office. The case was such an outrageous example of junk science in the courtroom that it was the subject of several newspaper investigations, a major story in The New Yorker, and a PBS Frontline documentary. Last spring, seven years after his death, a special state commission concluded that the forensic evidence in Willingham’s case was deeply flawed but failed to address whether the original fire inspector had been negligent.