Arson

1. Arson

2. So, what is the fascination with fire? Fire is just plain mesmerizing… How many of you like to watch a fire in a fireplace? …toasting marshmallows in a fire (even if you don’t eat them)?…..How many of you stare at a fire when it is happening?

3. Does our fascination with fire derive from our ancestors’ close relationship with fire for warmth, protection and light? It is believed by some that fire was first created by lightening. Caveman saw the fire and was attracted to it. Maybe they would have thought that a part of the sun had broken off and fallen to earth. It is believed that fire was first used and controlled by caveman about 1,420,000 years ago. 

4. In case of arson, it may simply be fire’s raw destructive power that fuels the attraction.

5. What is the science behind the fire? While there are millions of different chemical reactions, chemists tend to group them into three main types: precipitation acid-base oxidation-reduction

6. Oxidation The combination of oxygen with other substances to produce new substances Example: CH4 + 2O2 CO2 + 2H2O

7. 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 transfer of e- from the fuel to the oxygen in the air can be very energetic, and this energy is given off as heat and light; combustion. The reducing agent is simply the fuel. The oxidizing agent in most fires is oxygen.

8. Remember this?

9. Pop quiz: Which is the oxidizing agent and which is the reducing agent?

10. Ignition temperature The minimum temperature at which a fuel will spontaneously ignite… Ex: When you fill up your car with gas it comes in contact with the air but it does not ignite. Gasoline is stable at room temperature. The gas molecules must collide at higher speeds with oxygen to produce carbon dioxide, water and heat. For gas the ignition temperature is 536º F. Guess what your spark plugs do?

11. The three things needed to keep a fire going are fuel, an oxidizer, and heat. This is often called a fire triangle. If you remove any side of the triangle, the fire will go out.

12. Oxygen Heat O2 Fuel

13. Flashpoint The minimum temperature at which a liquid fuel will produce enough vapor to burn. The flashpoint is always lower than the ignition temperature.

14. Flammable Range The entire range of possible gas or vapor fuel concentrations in air that are capable of burning.

15. Glowing Combustion Burning at the fuel-air interface. Examples:

16. Spontaneous Combustion A fire caused by a natural heat-producing process in the presence of sufficient air and fuel

17. Spontaneous Combustion of the human kind Is this true? Can humans suddenly combust for no apparent reason?

18. September, 1982 In 1982, Jean Saffin, a 61 year old handicapped London woman, mysteriously burst into flames while resting on a wooden chair in the kitchen of her Edmonton home.  Her father was nearby and witnessed this event. The coroner held an inquiry into Jean's death, and no cause could be found for the fire.  The officer in charge reportedly told Jean's family that he believed the cause to be Spontaneous Human Combustion due to the circumstances, i.e. the very rapid ignition and burning of human tissue, but that he would look ridiculous if he reported this as a matter of permanent record.  

19. August, 1998 On August 24 1998, Agnes Phillips mysteriously caught fire while unattended inside her daughter's car.  Several people witnessed this event, and amazingly, the victim lived for a short time afterwards.   The documentation in this case reveals that Agnes's body was severely burned within a matter of minutes, essentially eliminating any possibility of this event being caused by a "wick effect" type of fire, thereby making this a likely candidate for a true Spontaneous Combustion case in modern times.

20. Whew! We’re done with the scientificy stuff!

21. So… the fire has started…. ….There is severe damage….The scene of the crime and the evidence seems destroyed by the fire….The firefighters themselves may have destroyed evidence in their efforts to contain the fire….. Now what?

22. An arson investigator, even among the ruins, seeks to answer 2 questions: Where was the fire’s point of origin? and What was the cause of the fire?

23. The arson investigator uses physical and chemical evidence to seek these answers. They may determine whether the fire was accidental or incendiary (intentionally set).

24. So…why would anyone want to commit arson??? What are some things that you could think of as reasons for committing arson?

25. Why are you guys so good at this? This scares me….

26. Some reasons that you may have mentioned… • Covering tracks (theft, murder…) • Insurance Fraud • Psychological reasons • Revenge • Suicide or murder • Terrorism

28. 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 500 - 2000ºF 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.

29. So, where did the fire start? After the fire engineer has given the OK to enter a fire scene, the forensic team gets to work collecting evidence. The chief fire investigator or fire marshal interviews witnesses who may have very important pieces of the puzzle. They may have seen enough to identify the point of origin or may have seen the color of the flame/smoke.

30. 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

31. How does a fire move? 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.

32. Stored fuels and other flammable liquids can interfere with the true point of origin. They can also be a problem for an investigator when arson with an accelerant is suspected since these items are also accelerants. Which was purposeful and which were stored?

33. 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.

34. Intensity of fire 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

35. 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 ever seen a burned log? Same thing.

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

37. So, how do you collect evidence? Most likely the accelerant of choice is some sort of petroleum-based hydrocarbon such as gasoline or kerosene. When collecting materials such as these, evidence must be placed in a metal container so no fumes diffuse through the container. You can lose your evidence quickly if placed in plastic.

38. Unfortunately, many linoleum flooring, carpet and tile adhesives have hydrocarbons in them so how can you tell what was there to begin with and what was added ‘for effect’? Ans: Collect unburned samples and compare

39. Sniffing work… in a technical way VTA – A Vapor Trace Analyzer is a portable gas chromatograph. It has a nozzle, a heating element and a temperature gauge. It simply samples the air near the site of a suspected accelerant and works its magic on the spot. This is used as a presumptive test for accelerants.

40. And then there’s the K9 squad…the best sniffers around town…

41. 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. • Solvent Extraction: Material is dissolved in a solvent. The hydrocarbons are separated out then analyzed.

42. Confirmatory Tests • Steam Distillation: Charred material is heated, the steam is collected, condensed and analyzed for hydrocarbons. • 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.

43. Analyzing Hydrocarbons • Gas Chromatography (GC) • Mass Spectroscopy (MS) • GC-MS combination

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

46. What position was the body in? (See the boxer’s posture 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.

47. The Boxer’s Posture 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 (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.

48. Just a small blast of explosive materials…. Fires and explosions are similar reactions (both from a combination of fuel and oxygen) but the difference is in the rate of reaction. Fires are slow burners and consume their fuel more slowly than explosions which consume their fuel almost instantaneously. This is a bummer for investigators since fragments of evidence is strewn all over the place.

49. Classification of Explosives Explosives are classified by the speed of their resulting pressure wave. Low explosives move at about 1,000 m/sec. High explosives may reach speeds as fast as 8,500 m/sec

50. The search is on…. Investigating an explosion is similar to a fire scene except that it requires more detail. Fragments from the device, the igniter and the timer may be crucial to determining the type of explosive used and to the type of person that made it.