1. ARSON = purposely setting fire to a house, building or other property.

2. U.S. Arson Stats Arson is the second leading cause of death by fire.
Estimated 500 Americans die in arson-related fires each year
Arson causes more than $2 billion in property damage each year.
Only 19% of arson cases resulted in arrest; Only 2% were convicted.

3. Cause of fire Natural Accidental Incendiary (intentional). Suspicious
Unknown

4. The Chemistry of fire
While there are millions of different chemical reactions, chemists tend to group them into three main types:
precipitation
acid-base
oxidation-reduction*

5. The Chemistry of fire
Fire is an example of an oxidation-reduction reaction (sometime called a combustion reaction).
In an oxidation-reduction reaction there is a transfer of electrons from one chemical… (the reducing agent) to another chemical… (the oxidizing agent).
The reducing agent is simply the fuel.
The oxidizing agent in most fires is oxygen.

6. Oxidation The Chemistry of fire
The combination of oxygen with other substances to produce new substances
Example:
CH4 + 2O CO2 + 2H2O

7. The Chemistry of fire

8. Pop quiz: The Chemistry of fire
Which is the oxidizing agent and which is the reducing agent?

9. The Chemistry of fire BASIC DEFINITIONS
Ignition temperature =Temperature at which a fuel will spontaneously ignite.
Flashpoint =Temperature at which a liquid fuel will produce enough vapor to burn.
Flashover =Auto Ignition from super heating.
Backdraft = Oxygen is missing…vacuum created

10. The Chemistry of fire BASIC DEFINITIONS
Pyrolysis = a decomposition reaction that produces small gaseous compounds to combust. All flame fires are burning vapors or gasses
Glowing combustion = smoldering: on the surface of a solid fuel like cigarette or wood
Activation energy = E required to start reaction
Exothermic = means to give off heat

11. The Chemistry of fire
The three things needed to keep a fire going are FUEL, OXIDIZER, and HEAT. This is often called a fire triangle. If you remove any side of the triangle, the fire will go out.

12. The Chemistry of fire
Oxygen Heat O2
Fuel

13. The Chemistry of fire Can you now explain FIRE EXTINGUISH
Can you now explain FIRE RETARDANT

14. The investigation of the fire scene
An arson investigator, even among the ruins, seeks to answer 2 questions:
1-Where was the fire’s point of origin?
and
2-What was the cause of the fire?
The arson investigator uses physical and chemical evidence to seek these answers.

15. Investigators may use witnesses’ reports to help:
The investigation of
the fire scene
Investigators may use witnesses’ reports to help:
Locate the point of origin
Determine whether the fire was accidental or incendiary
Figure out whether the arsonist used an accelerant

16. V The investigation of the fire scene Fire behavior
Fires typically spread sideways and up from the point of origin; a ‘V’ pattern where the bottom of the ‘V’ points to the origin.
It happens in a perfect scenario where there are no drafts, corners, stairwells, synthetic carpets, etc….these cause unusual burn patterns. The most damage is by the point of origin. V

17. Multiple points of origin
The investigation of
the fire scene
Multiple points of origin
This happens when an arsonist has started multiple fires within a building by either placing pools of accelerants in various locations or sloshes a path of accelerants.

18. The investigation of the fire scene
Stored fuels and other flammable liquids can interfere with the true point of origin.

19. The investigation of the fire scene Intensity
Materials melt or buckle at certain temperatures. A fire engineer would know that glass melts around 1,500ºF and that steel beams buckle wherever the most intense fire is located

20. The investigation of the fire scene Spalling
The crackling and flaking on the walls and floors in areas of high heat
Wooden structures will look charred and flakey.
Kind of what looks like black alligator skin… Have you seen a burned log?

21. The investigation of the fire scene Timing
Having a series of smoke detector helps. The alarms go off in sequence. This indicates the path of the fire.

22. The investigation of the fire scene
Sniffers
VTA – A Vapor Trace Analyzer
Is a portable gas chromatograph.
Presumptive test for accelerants.
K9 – 100% accuracy=Presumptive?

23. The investigation of the fire scene
The best sniffers… Dogs detect 0.01 microliter of 50% evaporated gasoline 100% of the time microliter is about the size of a thousandth of a drop.

24. Evidence Collection
Most accelerants are some sort of petroleum-based hydrocarbon such as gasoline or kerosene.
Evidence must be placed in a metal container so no fumes diffuse through the container.

25. Evidence Collection Control samples need to be collected
Many linoleum flooring, carpet and tile
adhesives have hydrocarbons in them.
Control samples need to be collected

26. Confirmatory Tests
Headspace vapor extraction: The vapor collected in the space above the material in a closed container is called the headspace. Heating the container really quickens the process. The vapor is removed with a syringe and analyzed for hydrocarbons via GC-MS
Solvent Extraction: Material is dissolved in a solvent. The hydrocarbons are separated out then analyzed via GC-MS

27. Confirmatory Tests
Steam Distillation: Charred material is heated, the steam is collected, condensed and analyzed for hydrocarbons via GC-MS
Vapor concentration: A sample is heated in a closed container with charcoal inside to absorb the vapors. The charcoal is removed, hydrocarbons are extracted and analyzed via GC-MS

28. Arson Motives Concealment of a crime (theft, murder…)
Insurance Fraud/Profit
Psychological reasons/Excitement
Revenge
Vandalism
Terrorism/Extremist
remember the NOVA video?

29. Fun Fact…
A person who thinks that they can cover up a murder with arson probably did not pass chemistry. Structural fires do not burn hot enough and long enough for a body to be completely destroyed. When a body is cremated, it needs to be exposed to temps around 1,500ºF for 2 or more hours. A structural fire can range from ºF but not for the amount of hours needed; simply not enough fuel. Its amazing how much a significantly burned body can be well preserved internally. The ME can even search for signs of trauma and poisons.

30. Investigating Homicidal Fires
Whenever a body turns up at a scene, the M.E. must determine the cause of death. At a fire scene the M.E. must answer the question:
Was the victim alive at the time the fire started?

31. What position was the body in. (See next slide
What position was the body in? (See next slide.) Are there items of significance around them?
What was the CO (carbon monoxide) levels in the blood and tissue? CO enters the blood and tissues when inhaled from the smoke. A normal level of CO in the blood is ≤ 5%. In victims of asphyxiation (suffocation) the level ranges from about 45 – 90. Also, too much CO in the lungs make you disoriented, unable to think or to move properly… and unable to escape.
Was there soot in the lungs? Soot enters the lungs when smoke is inhaled.

32. Many people believe that a body found curled up shows that the victim was alive the time the fire reached them and that they died a painful death. This isn’t the case. A burning corpse assumes a boxer’s posture called a pugilistic position….arms and legs flexed and fists tucked under the chin. Actually this happens because the muscles are dehydrating rapidly causing them to contract.

33. Profile of the Arsonist YWM
AGE: majority under 18 (51%) if adult, late 20s, almost never over 35
SEX: 9 out of 10 times (90%) a male
RACE: 3 out of 4 times (75%) a white; black (20%)
CLASS: majority from lower to working class
FAMILY: absent or abusive father, history of
emotional problems with family/mother
SCHOOL: learning problems and usually held back

34. Profile of the Arsonist
PEERS: social misfit, interpersonal problems with
opposite sex, appears physically and emotionally weak compared to peers
WORK: usually chooses subservient position and then
resents it.
CRIMINAL HISTORY: numerous offenses as juvenile, almost all have arrest records
ARREST: majority remain at crime scene; some attempt suicide in lockup; most will easily confess