Successful investigation of any crime largely depends on evidence. Stronger the evidence, stronger the case! Just like investigating any crime scene, solving an arson case also relies heavily on the physical evidence collected from the crime scene. However, investigating a fire scene is more complex because as fire spreads, it even destroys the evidence of its initiation. As such, the fire investigator should carefully observe even the minor evidence at the scene because they play a very important role in finding the origin of the fire.
Physical evidence implies concrete and tangible objects and not the abstractions, inferences, theories, and imaginings. These physical arson pieces of evidence will assist in solving the crime and also help in prosecuting the person criminally responsible. The investigator should follow the clues in the scene and its immediate vicinity in connection with the origin of the fire being investigated. This includes looking at the burn pattern, evidence of forced entry, missing accessories/components, or personal property, tampered objects, and more.
Here is some important evidence to look for while conducting an arson investigation.
- The direction and location of the flames will help you in locating the source of the fire. Though wind direction and construction materials affect the fire direction, make sure to remain vigilant. The fire point will take the process of investigation further.
- An experienced fire investigator has knowledge of fire and burns patterns. A professional can tell much about the fire by just looking at the color of the flames. By observing the height and color of flames, a fire investigator can determine some crucial factors. This means s/he will look how the flame color changes from red to yellow at different situations. The color of the flame determines the caloric value of certain substances which makes them emit a unique color during combustion.
- Collecting evidence is the most important step in the investigation process. It requires complete attention of the investigator so that nothing goes unnoticed. Every minor evidence matters, such as fingerprints, latent prints, tire tracks, footprints, hair, fibers, blood, and other body fluids.
- You will find some suspicious, as well as normal looking objects at the scene. Both are equally important from the point of view of investigation such as cigarettes, drugs, glass, wood, soil documents, etc. You should also check the devices like laptop, answering machines, and phones to identify any unusual activity. Also, look for firearms and other weapons, paints, and other personal items such as clothing, wallets, etc.
- The investigator should also consider the color of smoke which can help in determining the cause of ignition. The vapor/smoke produced by fire contains tiny particles of the fuel being burned. Thus, the color of the smoke may tell the investigator about the nature of the burning fuel. If you see thick and black smoke, chances are heavy carbon fuel such as gasoline is the cause.
- The investigator should make use of all his senses. Just like the color of flame and smoke tell a story, similarly, the smell also gives some clues. An experienced fire and arson investigator is familiar with different types of smell of gasoline, diesel fuel, tar or paint.
- Once the evidence has been recovered from the crime scene, work proceeds in the lab. The residue and soot recovered by the arson and explosion investigator will provide information about the accelerants or explosives involved in the crime. The presence of accelerants, such as gasoline, which is usually confirmed with analytical tests, should not be considered definite evidence. This is because most vehicles are powered by gasoline, and it is not unusual for someone to carry gasoline in a container in their car.