Arson is defined as the deliberate act of setting fire to a structure or wildlife area. Sometimes arson is done to illegally collect on home insurance. There are several departments and investigators who take part in a fire investigation such as:
Fire Department – The fire department has control of the fire scene until such time as the fire is completely put out. They may or may not be part of the actual fire investigation but will be expected to
contribute to a criminal case if necessary.
Fire Marshal – The duty of the fire marshal varies according to location but often they serve the public by enforcing building codes and fire investigations. They are usually experienced firefighters.
Arson Investigator – Investigates origins and causes of fires and
assists in the legal prosecution of arson cases. May or may not be a law enforcement professional. There are also private arson investigators who may be hired to perform an investigation.
Insurance Investigator – A private arson investigator who’s
responsibility is to determine if the fire was caused through natural or unnatural reasons. They represent the insurance company.
Unlike the fire marshal and the public arson investigator, the insurance investigator is not certified by the state. Instead they are certified by a private entity.
An arson investigation starts with the fire itself. Every fire must have a source of fuel, heat, and oxygen.
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In a naturally occurring fire none of the above will have been tampered with. However, in an arson case, there is any number of ways to
manipulate these three factors to create a fire. That is what arson investigators are looking for when they conduct their investigation.
An arsonist may tamper with the fuel by introducing flammable material such as bedding, curtains, or clothing. Or they may add
flammable accelerants such as kerosene, gasoline or alcohol, either by themselves, or in combination with a flammable material, such as
gasoline soaked rags.
They may also increase the oxygen content of a structure by opening windows or punching holes in ceilings and walls. Fire will follow the highest concentration of oxygen to its source. By ventilating a structure at the top and starting a fire at the bottom of the
structure, an arsonist can cause the fire to race upward. The fire will rapidly involve the whole structure rather than be confined to one room, creating considerably more damage in a shorter period of time.
A heat source can be a simple match or lighter, or a complex mixture of chemicals. All arson fires involve the introduction of a heat source.
A fire will not be considered an arson fire unless all other accidental reasons have been ruled out. In order to positively say that a fire was deliberately set, one of the three factors above must be proven to have been tampered with.
The Arson Investigation
An Arson investigation will start with the firefighters who were present at the scene. They are often experienced enough to know when something about the fire is “off” and can alert investigators to an area that should be looked at further.
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These observations may include such things as:
• Multiple points of origin (The fire started in more than one place)
• Presence of flammable accelerants such as gasoline or kerosene Normally in a criminal investigation the witness interviews are not done immediately, but after the physical evidence of the crime scene has been processed. In a fire investigation the firefighters and witnesses are interviewed immediately. They will want the answers to many of the following questions:
• What color was the smoke? The color of smoke can sometimes indicate what was burning.
o Gasoline produces a yellow or white flame with black smoke Wood produces a yellow or red flame and grey or brown smoke. If a burning wooden house is producing thick black smoke this could indicate the presence of gasoline. A large amount of gasoline being stored in a house is unusual and raises the suspicion that gasoline was used as an accelerant
• Did they notice fire systems such as sprinklers?
• Were there any signs of forced entry?
• Were the burning items present in the structure normal everyday items or was the structure empty of these items?
o An absence of normal items could indicate that the structure was emptied before the fire was started, indicating arson as a strong possibility.
Witnesses will then be questioned about what they saw, if they noticed anything unusual, saw anyone entering or exiting the structure, or knew of any other information that might contribute to the investigation.
Physical evidence is an important part of a fire investigation and often a faulty gas or electrical equipment is to blame for naturally occurring fires.
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If an accelerant was used by pouring over carpet, the floor below the carpet will have a distinct and characteristic pattern that can be removed and sent to the lab for analysis.
Explosion Investigations
Contrary to intuition, bombs do not make evidence disappear and forensic scientists who specialize in explosives can send minute
fragments to the lab for analysis and determine many useful pieces of information.
Bomb investigations will closely resemble fire and arson investigations.
They will both have:
• A high safety priority,
• Will involve a physical change in materials like the conversion of solid or liquid into gas, and/or the conversion of small quantities of matter into energy.
• Involve a chemical change or reaction which causes a rearrangement of atoms.
• Must take place in the presence of oxygen
Bomb investigators must be very well educated in chemistry and
physics in order to accurately determine the reactions that took place, as well as the mechanics of the explosion.
Some of the most common explosive devices seen are homemade pipe bombs which use nothing more than black powder from shotgun shells and a metal pipe.Much more complex are explosives using TNT
(trinitoluene) or nitroglycerin. Nitroglycerin is found in dynamite, which combines sodium nitrate, nitroglycerin, and other non-explosive, or inert, compounds. One type of explosive is ammonium nitrate, used in the 1993 World Trade Center bombing and the 1995 Oklahoma City bombing. Combined with fuel oil, it is known as ANFO, a foul-smelling—
and lethal—sludge.
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Simple pipe bombs do not require a detonator device or timer, but the more sophisticated types of explosives to. This timer or detonator can be very complex, or very simple.
Forensic investigators familiar with explosives will be able to find very small remnants of the bomb and be able to reconstruct the components using very sophisticated equipment. If you have ever taken physics you might remember the first law of thermodynamics which states:
Energy can neither be created nor destroyed.
That means that there will ALWAYS be evidence of explosions, even though it might be invisible to the naked eye.
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