by Monica Bennett about a year ago in guilty

A Layperson's Introduction


All violent crime is about power, and arson is no exception. When you imagine the devastating fury of uncontrolled flames, you are imagining an exercise of power that boggles the mind. Whether the arsonist is professional or an amateur, he follows the pattern of obtaining power; demonstrating it, maintaining it, and acquiring lost power. Statistics for arson fires are alarming. From 2010 until 2014, the latest years for which this information is available, there were 261,330 arson fires in the United States. Fatalities number 440, 1,300 injured, and one billion dollars in property damage. There are 20 offenders per 100,000 people. Most of these fires, a full 50 percent, occur at night. Motives include; thrill-seeking, vandalism, concealment of another crime, profit, revenge, attention seeking, hero complex, politics, terrorism, and mental illness.

Flame Lover

Many people will chalk up any act of vandalism as pyromania. That is not so. True pyromania is rare. It actually falls into the diagnostic paradigms of impulse control disorders, with dysfunctions like kleptomania (stealing), intermittent explosive disorder and pathological gambling. These disorders are marked by a failure to resist impulses, such as the impulse to light a fire. A pyromaniac experiences arousal, gratification, and/or relief when setting a fire.

There is a standard profile for the typical offender;

  • White male, age 17-26
  • Unstable childhood
  • Childhood hyperactivity disorder
  • Poor performance in school
  • Antisocial behaviors and other crimes as an adolescent
  • Poor marital relationship
  • If not married, still living at home with parents
  • Weak social skills
  • mployed in low-paying jobs
  • Poor military performance
  • Fascination with firefighting
  • Substance abuse

Point of Origin

The most important part of a fire investigation, whether it is accidental, natural, or intentional, is the point of origin. In the picture above, it is the back wall of the room. How do you know? It is the area of greatest damage. The fire burns hottest here, and longer. Sometimes it is difficult to find, and sometimes it is completely destroyed. There are hints of where to look when an investigator arrives at a fire.

Melted Glass

Bottles, glasses, chandeliers, and other glass items will melt in the direction the fire came from, pointing out the fire's path. Furniture, walls, rugs and other household items can also give the direction.

Direction of Burn

Evidence of arson can be found at the point of origin. They include fuel sources (wood, plastic, clothing, drywall, etc.), incendiary devices, and pools of accelerant. Fires tend to burn upwards, therefore the point of origin is likely to be found at a lower point of burn damage. However, this is not always true. Certain fuels can cause a downward burn. V-shaped patterns made of smoke or fire may be found on walls, with the bottom of the V pointing to the place where ignition occurred.

Fire occurs due to the exothermic reaction of combustion (burning), producing heat and light. Three vital components must be present: a fuel source, an oxidant (O2), and ignition. Ignition cannot take place unless a solid or liquid undergoes pyrolysis. That means it must be forced into a gaseous state. A match will burn paper, but not a 2x4 because there isn't enough heat to make the wood give off vapors that actually burns.

Flammable liquids commonly used in arson are diesel, kerosene, and turpentine. The use of accelerants is suggested by localized burning patterns with a demarcation between burnt and unburnt areas, multiple points of origin, or trail marks that link points of origin, and the detection of hydrocarbon vapors using sniffer dogs or hydrocarbon detectors. Hydrocarbon sniffers are vapor detectors used to discover the presence of fuel vapors associated with flammable liquids. Amateur arsonists are prone to dumping large volumes of flammable liquids in a helter-skelter fashion. When large amounts of liquids are used, there will be pour marks left behind that show exactly where the substance was put.

Pour Patterns on Linoleum

The professional and the amateur arsonist alike want to produce a maximum of destruction. The intelligent arsonists will be sure there are the fundamental requirements for a large, spreading fire: ready availability of fuel, proper ventilation, and reliable ignition. Much is made of ignition devices in movies like Backdraft, but only about 12 percent of arsonists ever use them. Certainly not the elaborate ringing phone or the electrical outlet scenario of the film. It is only when a delayed ignition is required, which happens when an offender needs time to get out of the way in, say, a large warehouse or department store. This is a crime Americans pay the cost of every day. The price of arson is reflected in everything we buy, and the taxes that we pay. Fire suppression is not cheap, and neither are the lives lost.

How does it work?
Read next: Eliminating Bail
Monica Bennett

I am a retired high school and college teacher. I have taught forensics, biology, chemistry, ecology, and Earth science.. Long Island has been my home for 60 years.

See all posts by Monica Bennett