NORTHAMPTON - There's a simple rule for detectives in an arson investigation: Get to the scene fast.

Alejandro Sanchez Jr., a former arson investigator for the Springfield Police Department and part-time officer in Sunderland and Hatfield, said in suspicious fires, evidence can be destroyed quickly by flames or, accidentally, by emergency and utility responders.

And the longer it takes an investigator to reach the fire, the greater the possibility that early witnesses will leave the scene, he said.

On Sunday, about 20 suspicious fires were set within a half-mile radius in Ward 3, near the city's downtown. Local, regional, state and federal agencies are investigating the multiple blazes that killed a father and son, and destroyed two homes and a number of cars.

Arson can be one of the more difficult crimes to investigate because of the destructive nature of fire, not to mention the water and foam used to quell flames. Discovering a motive for the intentionally set fire can help an investigation come to completion, but without a motive, suspects may be hard to identify.

Motives for arson include revenge, excitement, vandalism, concealment of a crime and profit, which can involve insurance fraud and stop loss, according to the book "Profiling Violent Crimes: An Investigative Tool," published by Sage, a scholarly press.

It is unclear if a motive for the Northampton arsons has been identified. The Northwestern district attorney's office, which is leading the investigation, has not issued a statement on motive.

"In Northampton, I don't know if there is a connection between all the victims," said Sanchez, who is also a criminal justice professor at Holyoke Community College. "If there isn't, then that's going to make it harder to profile the arsonist."

First things first

When investigating an arson, the first thing to be determined is the origin of the fire, Sanchez said. In some cases this can be done while the fire is still burning. The origin is usually the area that has burned the longest, said Jennifer Mieth, spokeswoman for the state Department of Fire Services.

"Every fire is different," she said, "but fire investigators have to take the same steps for every fire."

Investigators will survey the area from least to most burnt, analyzing evidence that ranges from the obvious, such as an empty gas canister, to eyeing char patterns. Char patterns can provide clues such as whether an accelerant, such as gasoline or lighter fluid, was used, among other details.

Detectives also make other on-scene observations to determine things such as whether someone forced their way into the structure that was set on fire. They also try to identify whether the fire was started with an incendiary device, such as a wick, remote control, pressurized container or match.

"It's a difficult crime to solve, but it's getting easier because we are more knowledgeable about the science of fire," said Michael Lane, vice president of Corporate Investigative Services, a private fire investigation firm with offices in New York and Vermont. Lane said he has 35 years' experience in the field of fire investigation.

"A fire investigation is like a big puzzle that you have to put back together," Lane said.

Detectives then round up witnesses and victims on scene to get statements. Firefighters are also usually interviewed, said Lane.

"Sometimes the scene can be altered by the firefighting efforts, like how they ventilated a building or how they used their hose lines when they came in," Lane said. "You have to ask them what they saw when they came in."

Among the questions an arson investigator might ask during an interview are: the color of the smoke (which may help to identify if an accelerant was used); whether the alarm, sprinkler or fire detecting system was working; and whether anything was missing from the burnt structure (which may indicate someone had advance knowledge of the fire and was trying to preserve an item or items).

Sanchez said getting neighbors or witnesses to cooperate with law enforcement can be difficult following an arson, because people fear retribution. In his 22 years as a police officer, Sanchez said he has rarely heard of a suspect taking vengeance on a witness for any crime. He said television shows and movies make retribution seem more probable than it is.

"People think, even if a person is caught and arrested and even if they do time, there will be a time when they will be free, and most witnesses think that person will retaliate," Sanchez said. "I don't know how true that is. You don't hear about it that often in this area.

Expert: 'Come forward'

"People should come forward," he added. "Even the smallest clue could be very important."

Investigators will also search the crowd at the fire looking for people acting out of the ordinary. Some arsonists stay to watch their fires or assist firefighters in extinguishing the blaze.

"Detectives are also required to canvass the area during the fire and see if there is someone out of the ordinary watching," Sanchez said.

After the fire is extinguished, investigators can begin a forensic examination of the scene, taking scraped samples from the floor, walls or anywhere else the fire appears to have started.

The evidence is placed in a metal container and submitted to the state crime lab for analysis. Sanchez said at this point investigators are primarily looking for accelerants.

Lane said accelerants are becoming less common at arson scenes because forensic science allows law enforcement officials to easily identify the substance.

"Labs are much better now," Lane said. "You can find 2 parts per million of gasoline in a lab."

Investigators also consider details such as how materials inside a building or vehicle burned and whether they burned at a rate and pattern standard for the substance. Accelerant-sniffing dogs can be brought on the scene and computer models that can demonstrate how a fire was affected by things such as wind conditions can also be used to solve an arson.

The financials

Standard criminal investigation techniques are also incorporated into arson cases. Lane and Sanchez said investigators will research financial details pertaining to the subject of arson. For example, they might look into whether a home that burned down was in foreclosure, or whether a car that was set on fire needed more repair work than it was worth.

"That's the kind of stuff we investigate, but hopefully someone comes forward with a lead," Sanchez said. "Everyone has to do their part."

There's no standard length of time for an arson investigation. In some instances it can take months or years to crack, said Lane. Sometimes, law enforcement officials have to wait for the arsonist to set another fire before he is caught.

"The trouble is that often they'll be someone who won't do it (set a fire) in a while," Lane said, "and then something gets to them and they start starting fires again."

About 62,800 arsons were reported in the United States in 2008, the most recent information available from the Federal Bureau of Investigation. The average dollar loss per arson was more than $16,000.

In 2008, about 13 percent of arson cases were "cleared" (a federal law enforcement term that can indicate a case being closed by arrest, formal charges, or identifying an offender, among other possibilities), according to the FBI. The figure may seem low, but it is equal to the percentage of all property crimes cleared that year.

Across the nation, arsons were cleared more often in 2008 than motor vehicle thefts or burglaries.

Kristin Palpini can be reached at kpalpini@gazettenet.com.