Arson Investigation Fire Basics Three Main Components Needed
Arson Investigation Fire Basics
Three Main Components Needed to Sustain a Fire 1) Fuel 2) Oxygen 3) Heat
Fuel A combustible material in any state of matter (solid, liquid or gas). Example: Clothing, Furniture, Alcohol, Paper, Etc.
Oxygen The air we breathe is about 21% oxygen. Fire requires an atmosphere with at least 15 – 16% oxygen.
Heat Energy needed to increase the temperature of the fuel to change into the vapor state for ignition to occur. Examples: Stoves, Fireplaces, Damaged Wires
Fire Investigation Terms Fire – Produced when a substance undergoes rapid oxidation involving heat and light. Fire Triangle – Shows the three elements needed to produce and sustain a fire. Flash Point – The lowest temperature to which a substance must be heated in order for the substance to give off vapors which will burn when exposed to a flame or ignition source.
Fire Investigation Terms Point of Origin – The location where the fire started. Burn Patterns – Noticeable patterns created by the fire as it burns. Accelerants – Substances, such as gasoline, paint thinner and alcohol, that accelerate the burning process. Arson – A fire started deliberately.
Obvious Problems of Investigating Arson 1) Difficult to evaluate a scene. 2) Scene and the crime are severly damaged, if not completely destroyed. 3) Efforts of firefighters may destroy evidence.
Successful Arson Investigation 1) Using physical and chemical evidence: a) Find the Point of Origin b) Determine what caused the fire. 2) Determine if the fire was accidental or incendiary (intentionally set)
Common Reasons for Arson 1) Covering their tracks: Cover theft, embezzlement, murder, financial records, etc. 2) Insurance fraud: Monetary Gain Need quick money Insurance greater than the property’s marker value Usually remove valuables and then try to claim insurance
Common Reason for Arson 3) Psychological reasons: Mentally Disturbed To fulfill some deep-seated psychological need Pathological love of fire may lead to starting structure or forest fires Usually turns into serial offense
Common Reasons for Arson 4) Revenge: Malicious Vandalism Cause for burning someone’s house or business 5) Suicide or Murder: Bodies usually found in fire were dead before fired started. Fire is too painful for suicide. Fire is too unpredictable for murder.
Common Reasons for Arson 6) Terrorism: Create fear or make political statement.
How First Responder’s Impact The Fire Investigation They write down what they take note of when they arrive at the scene: 1) Observe 2) Preserve 3) Document 4) Communicate
Fire Investigation Basics Time is the enemy: Many volatile substances that cause or accelerate a fire rapidly dissipate.
The Basics 1) Work from the least damaged areas to the most heavily damaged areas. 2) Document with notes, photographs and videos. 3) Collect evidence (accelerant samples, fire items, and other crime scene evidence) 4) Interview witnesses – including first responders
The Basics 5) Determine the point of origin – requires understanding of how fire moves through the structure. 6) Determine the heat source. 7) Hypothesize the reasons for the fire.
Collecting Evidence Four methods accepted in court: exigent circumstances, consent of property owner, administrative search warrant, criminal search warrant. Evidence containers – metal cans, glass jars or special evidence bags. Through Observations, Experiment
Collecting Evidence Use of Dogs or VTA – Vapor Trace Analyzer Collect unburned materials for comparison purposes
Point of Origin Determining the point of origin requires understanding of how fire moves through a structure 1) Fire moves horizontally and vertically from point of origin 2) Follows path of least resistance
Hypothesize the reasons for the fire. Subjective or speculative info cannot be included. Only facts that can be clearly proven by observation or experiment.
Fire Clues 1) Point of Origin – burn patterns and other damages can help determine the point or origin, or the location where the fire started. 2) Char Patterns – created by very hot fires that burn very quickly and move fast along its path, so that there can be sharp lines between what is burned and what isn’t - a char pattern on a door would help an investigator determine which side of the door the fire was on - a char pattern on the floor would help investigators determine the use of an accelerant and its path.
Fire Clues 3) V Patterns – Fire burns up, in a V-shaped pattern, so a fire that starts at an outlet against a wall leaves a char pattern that points to the origin. - a very narrow V-shape might indicate a fire that was hotter than normal, such as one helped along by an accelerant. A wide V-shape might indicate a fire that was slow burning. A U-shape could indicate that there was a “pool or origin” rather than a point of origin, such as might be caused by , say, a puddle of gasoline.
Fire Clues 4) Heat Shadows - occur when heavy furniture shields part of a wall; can help determine the origin part. 5) Glass – glass fragments, windows, and light bulbs can provide clues to a fire. - light bulbs tend to melt toward the heat source, so the “direction of melt” can indicate the direction of the fire.
Fire Clues - the shattered or cracked glass of the windows can provide indications as to how a fire burned. - a dark soot layer on the glass could indicate a slow, smoldering fire. - clear glass with an abnormal pattern of cracking could imply a very hot fire, possibly due to an accelerant.
Fire Clues 6) Chimney Effect – since fire burns upwards, there can be a “chimney effect” where the fire ignites at a point, the superheated gases rise upward and form a fireball, which continues straight up to burn a hole in the ceiling. If the rood is not entirely burnt, and the fire investigator finds such a hole, the origin of the fire could be directly underneath.
Fire Clues 7) Color or Smoke- determine what type material was burning. 8) Color of Flames – indicates at what temperature the fire was burning.
Accident or Arson Accidental: 1) heating system 2) electrical appliances 3) lightning 4) children playing with matches 5) smoking
Non- Accident 1) Odors – gas, kerosene, or other accelerants 2) Furnishing – removal of personal objects and valuables 3) Clothing – check debris for buttons, zippers 4) Locked windows, blocked doors 5) Two or more points of origins
Non - Accident 6) Look for inverted V-patterns 7) Floors charred – can indicate use of an accelerant 8) Trailers that lead the fire form one place to another
Arson Facts in America According to the FBI Crime index, juvenile and adult arson cause an annual average of 560, 000 fires, 750 deaths, 3, 700 injuries and 1. 5 billion in property loss. 55% of all arson arrests in the US are children under 18.
Juvenile Firesetting Fires set by juveniles are usually the result of a child or teenager experimenting with fire with lack of understanding of the consequences. Other are a cry for help or as acts of vandalism. In typical year, in the US, 300 people are killed and 190 million in property is destroyed in fires set by children.
Can Structural Fires Destroy a Body? No! Do not burn hot enough Bodies can remain well preserved internally Medical examiners can still search for sign of trauma and poisons.
Investigating Homicidal Fires 1) Determination of the position of the body was found in Use items around the body as well 2) Carbon monoxide levels in the blood and tissues Asphyxia – primary cause of death in fatal fires. High level of CO = died from smoke
Investigating Homicidal Fires Low level of CO = dead before or at the time of the fire 3) Presence or absences of soot in the lungs and airways Similar to CO levels
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