Fire and Arson Investigation: Comprehensive Study Notes

Understanding Fire Oxidation Reaction (Combustion)

• Fire is defined as "The rapid oxidation of a fuel that produces heat and light in various intensities."

• It is a combustion process involving the release of energy.

• Its visible form is often observed as flames.

The Fire Tetrahedron

• For fire to occur, four conditions must coexist:1. Oxygen

  2. Heat

  3. Fuel

  4. Chain Reaction

Conditions Required to Sustain Combustion

1. Fuel or Combustible Material: Presence of material that can burn.

2. Sufficient Heat to Raise Material to Ignition Temperature: Enough energy to initiate the reaction.

3. Release of Fuel Vapors Enough to Sustain Combustion: The fuel must vaporize to continue burning effectively.

4. Uninhibited Exothermic Chemical Chain Reaction: A continuous self-sustaining chemical process that releases heat.

• The science of fire prevention is based on the removal of one or more of these components.

Key Terms in Fire Investigation

• Accelerant:- A fuel, usually a flammable liquid.

  • Used to start, increase the intensity, or spread of a fire.

• BTU (British Thermal Unit):- Standard measure of heat energy.

  • Defined as the heat energy required to raise the temperature of $1\ \text{lb.}$ of water by $1\ \text{degree F}$.

• Exothermic Reaction: Chemical reaction where heat is given off.

• Endothermic Reaction: Chemical reaction where heat is absorbed.

• Combustible Material: Any material that will ignite and burn when sufficient heat is applied.

• Flammable Liquid: A liquid having a flash point below $100\ \text{°F}$.

• Combustible Liquid: A liquid having a flash point at or above $100\ \text{°F}$.

• Flash Point:- The minimum temperature at which a flammable vapor will ignite.

  • Examples:- Gasoline: $45\ \text{°F}$ ($7.22\ \text{°C}$)

    • Kerosene: $100\ \text{°F}$ ($37.78\ \text{°C}$)

• Fire Point:- The temperature at which a liquid produces vapors that will sustain combustion.

  • Generally higher than the flash point.

  • Examples:- Gasoline: $495\ \text{°F}$ ($257.22\ \text{°C}$)

    • Kerosene: $110\ \text{°F}$ ($43.33\ \text{°C}$)

• Ignition Temperature (Autoignition Temperature):- The minimum temperature to which a substance must be heated to ignite independently of an external heat source.

• Pyrolysis:- Decomposition brought about by high temperatures.

  • A chemical breakdown by heat causing the formation of vapors and a residual solid.

  • Example: Manufacture of charcoal (wood undergoes pyrolysis).

Categories of Combustion

1. Diffusion Flames:- Most natural flames.

   • Fuel and oxidant mix at the point of combustion.

   • Examples: Candle, fireplace.

2. Premixed Flames:- Combustion of fuel with oxygen where fuel and oxidant are mixed prior to combustion.

   • Example: Jet fuel (in a jet engine).

3. Smoldering:- A slow, flameless form of combustion.

   • Characterized by heat and smoke, often occurring on the surface of porous fuels.

   • Example: Glowing embers of coal briquettes.

4. Spontaneous Combustion:- Combustion without an external ignition source.

   • Caused by an internal heat-generating process (e.g., bacterial action, chemical oxidation).

   • Example: Haystacks igniting due to heat from bacterial decomposition. Spontaneous Human Combustion (SHC) is a debated phenomenon related to this concept.

Forms of Heat Transfer

1. Conduction:- Thermal energy passes directly from a warmer to a cooler area within a substance or between substances in direct contact.

   • Occurs through molecular vibration and collision.

2. Convection:- Transfer of heat energy due to the movement of a liquid or gas (a fluid) from a warmer to a cooler area.

   • Example: Convection oven circulates heated air using a fan.

3. Radiation:- Transfer of heat energy via electromagnetic waves.

   • Does not require a medium for transfer.

   • Travels from a warmer to a cooler area (e.g., heat felt from a campfire).

Phases of Fire

Fires typically progress through four distinct phases:

1. Incipient/Ignition Phase:- Low heat output.

   • Some smoke production.

   • No detectable flame (or very small, localized flames).

2. Growth Phase:- Increased heat output.

   • Lots of smoke production.

   • Flames begin to spread across fuel sources.

3. Fully Developed Fire Phase:- Massive heat output.

   • Lots of smoke.

   • Extreme flames, often affecting all available fuel in the compartment (flashover may occur).

4. Decay Phase:- Decreased flames and heat as fuel is consumed.

   • Continued smoke production.

   • Often characterized by smoldering remnants.

Major Complications in Fire/Arson Scene Investigations

• Qualified Investigators: Requires specialized training and experience.

• Fire is Destructive: Fire itself destroys or alters evidence.

• Many Agencies Involved: Coordination issues can arise.

• Bifurcated Responsibility: Division of duties between fire and law enforcement often leads to confusion.

• Lack of Commitment: Pervasive belief that fire destroys all evidence can lead to inadequate investigation efforts.

Fire Scene Protocols

• First Priority: Safety of people present at the scene.

• Major Objective: Determine the point of origin of the fire.

• Caution: Do not enter a potentially unsafe fire scene.

Search of a Fire Scene: Signs of Arson

Investigation focuses primarily on finding the origin of the fire and identifying signs of arson:

• Odors (Transient): Smell of accelerants (e.g., gasoline, kerosene).

• Separate, Unconnected Fires: Multiple points of origin suggest intentional setting.

• "Trailers": Patterns indicating spread of flammable liquid connecting multiple points.

• Burn Patterns: Peculiar or unusual patterns (e.g., pour patterns, V-patterns).

• Timing Device: Remnants of devices used to delay ignition.

• Containers: Empty cans, bottles, or other vessels that held accelerants.

• Tools: Tools used to gain entry or disable safety systems.

• Ignition Devices: Matches, lighters, electrical devices used for ignition.

• Accelerants: Presence of flammable liquids or other materials used to ignite or intensify the fire.

Types of Burn Patterns

• Pour Pattern: Distinctive pattern left by a flammable liquid being poured.

• "V" Pattern:- A common pattern where flames tend to burn upwards in a V-shape, pointing to the origin.

  • Factors that can distort V-patterns include:- Drafts/winds

    • Secondary fires due to collapse

    • Stairways/elevator shafts (which can act as chimneys)

    • Holes in the floor

• Alligatoring:- A pattern of charring on wood surfaces resembling alligator skin (large shiny blisters).

  • Can indicate intense, rapid heat, but can be misleading.

  • Factors affecting "Alligatoring":- Type of wood

    • Dryness of the wood

    • Weathering of the wood

    • Artificial treatments applied to wood

• Charring:- Oxidation and heat decomposition of materials.

  • The depth of charring can be used to track the course of the fire, but distortion can occur.

  • Secondary fires can complicate interpretation of charring.

Techniques to Find Accelerants

1. Photoionization Detector (PID):- A common instrument used to detect volatile organic compounds (VOCs) and other gases.

   • Measures concentrations from sub parts per billion (ppb) to $10,000\ \text{ppm}$.

   • Efficient, inexpensive, produces instantaneous readings, and operates continuously.

   • Commonly used as detectors for gas chromatography or as hand-held portable instruments.

   • Most common accelerants detected include gasoline and kerosene.

2. Canine Units (Dogs):- Specially trained dogs can detect accelerants in concentrations as low as $1\ \text{part per million}$ ($1\ \text{ppm}$).

3. Heat Distortion:- Distortion of objects due to heat can indicate the direction from which flames originated.

   • Example: Light bulbs will bend or bulge towards the source of the flames.

Collection & Preservation of Arson Evidence

• What to Collect: Ash and soot debris from the point of origin, particularly porous materials like wood, rugs, and rags.

• Containers: Collect evidence in airtight containers, such as clean gallon paint cans, to prevent the loss of volatile residues.

• Chain of Custody: Meticulously document who collected, handled, and transferred the evidence, including descriptions of the evidence and burn site.

• Control Samples ("Substrate Control"):- Necessary to acquire substrate controls from areas near the point of origin but not exposed to accelerants.

  • These samples help confirm that any detected accelerant is not a natural component of the burned material.

  • Also, clothing of suspects might be collected.

Hydrocarbon Classification

Accelerants are often ignitable liquids, which are hydrocarbons. They are categorized into five classes based on their boiling range:

• Class 1: Light Petroleum Distillate (LPD) (e.g., some lighter fluids)

• Class 2: Gasoline

• Class 3: Medium Petroleum Distillate (MPD) (e.g., mineral spirits, paint thinner)

• Class 4: Kerosene

• Class 5: Heavy Petroleum Distillate (HPD) (e.g., fuel oil, diesel fuel)

Analytical Techniques for Accelerant Detection

• Gas Chromatography (GC):- Considered the most reliable method for detecting and identifying flammable residues in arson evidence.

  • Separates volatile components based on their different affinities for a stationary phase and a mobile gas phase.

  • The resulting chromatogram provides a unique chemical fingerprint for different ignitable liquids.

• Heated Headspace Schematic:- Evidence (debris) is heated in an oven, causing volatile vapors (accelerants) to be released into the headspace above the sample.

  • These vapors are then sampled and injected into a GC.

• Passive Headspace Schematic:- A charcoal strip is suspended in a container (e.g., paint can, flint glass Pasteur pipette) above the debris.

  • Volatile vapors are adsorbed onto the charcoal strip.

  • The strip is then washed with a solvent to extract the adsorbed residues, which are then analyzed by GC.

Arson Laws (New York State Example)

In New York State, arson offenses are defined and categorized by severity:

• § 150.00 Arson; definitions:- "Building" includes any structure, vehicle, or watercraft used for overnight lodging or business. Separately secured units within a building are not deemed separate buildings.

  • "Motor vehicle" includes vehicles propelled by power other than muscular power on public highways, excluding invalid chairs, rail vehicles, and snowmobiles.

• § 150.01 Arson in the fifth degree:- Intentionally damages property of another without consent by intentionally starting a fire or causing an explosion.

  • Class A Misdemeanor.

• § 150.05 Arson in the fourth degree: E Felony

• § 150.10 Arson in the third degree: C Felony

• § 150.15 Arson in the second degree: B Felony

• § 150.20 Arson in the first degree: A-I Felony- These statutes typically involve greater degrees of intent, property value, risk to life, or use of incendiary/explosive devices.

Motives for Arson

• Revenge: Against an individual, business, or group.

• Vandalism: Destruction of property for no clear material gain, often by juveniles.

• Profit: Insurance fraud, concealing financial distress.

• Concealment of Another Crime: Destroying evidence of theft, murder, or other offenses.

• Excitement: Thrill-seeking or a desire to witness the fire.

• Terrorism: Using fire to instill fear or achieve political goals.

• Pyromania: A rare mental disorder characterized by an impulsive desire to set fires.

Challenges in Proving Arson in Court

• Low Arrest Rate: Arrests occur in only about $10\%$ of all arson fires.- Main Reasons: The destructive nature of fire and misconceptions.

• Destruction of Evidence: Time and water (used for suppression) are significant factors that destroy or contaminate evidence.

• Myth About Fire: The belief that "fire destroys all evidence" is a common misconception among firemen and police, leading to inadequate scene processing.

• Key elements for proving arson:- Establishing the Origin & Cause of the fire.

  • Presenting Evidence & Motive.

  • Demonstrating the defendant had the Opportunity to Commit the crime.

Types of Evidence Collected in Arson Cases

• Trace Evidence: Hair, fibers, blood, soil, glass fragments.

• Physical Evidence: Tools, tool marks, accelerant containers, rags, ignition devices.

Forensic Fire Scene Investigation Purpose

• To document visual observations accurately.

• To authenticate physical evidence through proper chain of custody.

Legal Standards Related to Arson Investigations

• Daubert Standard:- Applies to expert witness testimony.

  • Requires that the information presented by an expert witness be both reliable and relevant.

  • Emphasizes the use of sound scientific methods and principles.

• Michigan v. Tyler (Supreme Court Ruling):- Once a fire has been extinguished and firefighters have left the scene, a warrant is required to re-enter the premises for further investigation.

  • Exceptions: Consent from the owner or if the premises is abandoned.

  • This ruling emphasizes the Fourth Amendment protection against unreasonable searches and seizures in fire scenes.