For federal prosecutors, it was a "50-50" case, a coin flip, and they did not want to go forward with such odds, particularly as witnesses began to waver, the ATF agent said.
That same year, authorities arrested a man in connection with the destructive Laguna Beach fire -- only to release him when they determined he had been in a Mexican jail when the blaze started. That fire, which destroyed more than 300 homes, remains unsolved.
In 1985, investigators struggled from the beginning in the fruitless search for the motorist who dropped flares on brush along La Brea Avenue in Baldwin Hills, sparking a blaze that burned dozens of homes and killed three people.
Joe Riehl, chief of the ATF's arson division, said an experienced arsonist is an elusive culprit. He pointed out that the 2005 arrest of a man responsible for almost 300 fires in the Washington, D.C., area took a multi-level deployment of expert investigators two years.
Timothy G. Huff, a retired FBI violent-crime analyst who specialized in arson and bombing cases, was with the agency when it and the ATF conducted a major study of arsonists in the 1990s. He said arsonists' motives have included revenge, extremist beliefs, monetary gain and the desire for excitement. Revenge -- against an individual, institution or group -- seems the most common, he said.
The most sophisticated arsonists, he added, frequently are firefighters themselves.
A case in point was John Orr, a renowned Glendale fire captain and arson investigator who set dozens of blazes throughout Southern California and was the subject of Joseph Wambaugh's book "Fire Lover."
In an interview, Wambaugh said Orr was caught after a 1987 Bakersfield fire in which he uncharacteristically left a clue. At the scene, investigators found a yellow piece of notebook paper that was part of an incendiary device. The paper bore a fingerprint. A Bakersfield fire captain, Marvin Casey, who suspected a firefighter was the arsonist, tried to identify the print, but a database in Sacramento could not make a match.
Three years later, the ATF matched the print using a Los Angeles database containing Orr's fingerprints from a decades-old application to become a police officer.
It didn't help Orr's case when an unpublished novel he wrote, "Points of Origin," seemed to outline how he went about setting fires.
"His character is a firefighter who is an arsonist, and he described in living color what it was like to set arson fires," Wambaugh said.
Orr was sentenced to 30 years in federal prison for setting fires nearly identical to the ones he described in the novel. Six years later, in 1998, he received a life term for a 1984 blaze in South Pasadena that killed four people.
"John was a legend. For him, I think, it was the thrill of being a hero," said the ATF's Carroll.
With the Southern California wildfires dominating local and national news last week, tips regarding the four-year-old Old fire have increased dramatically, said Bell, the homicide investigator. He sought to allay any fears those with information might have about not speaking up sooner.
"If someone can come forward who knows something, they're not going to be in any trouble from us, even if they sat on the information for years," Bell said. "We're not going to go after that person. Our goal is to find the person responsible for lighting the fire."