1. CHAPTER 4 ARSON AND FIRE INVESTIGATION

2. INTRODUCTION—OBJECTIVES 1. Define combustion reactions 2. Discuss the four factors that are required to ignite and maintain a fire 3. Explain the conditions in which fuels will burn 4. Examine reasons why arson is difficult to detect 5. Identify the four categories of fire 2

3. INTRODUCTION—OBJECTIVES 6. Evaluate the significance of burn patterns discovered at an arson investigation. 7. Discuss the proper methods for detecting, collecting, preserving, and analyzing arson evidence. 8. Describe the psychological profile of an arsonist. 9. Examine the various motives for arson. 3

4. COMBUSTION  Combustion reactions — oxidation reactions that involve oxygen and produce flames  Heat of combustion — excess heat energy  Exothermic reactions — chemical reactions that release heat 4

5. THE FIRE TETRAHEDRON Four ingredients are required to start a fire and keep it burning  Oxygen  Fuel  Heat  Chain reaction 5

6. FLASH POINT & IGNITION TEMPERATURE  Most accelerants are hydrocarbons in a gas state  In a gas state, molecular bonding is weaker  Vaporization — liquid changes to gas  Flash point — lowest temperature at which vaporization occurs 6

7. FLASH POINT & IGNITION TEMPERATURE 7

8. ARSON IS DIFFICULT TO PROVE $15 billion of property damage a year in United States Can be accidents, but if not… What makes it hard to prove? 8

9. FUNCTION OF A FIRE INVESTIGATOR  Investigation must begin quickly, before evidence is lost  Find the fire’s point of origin  Examine possible causes  Accidental  Arson  Classify the fire 9

10. FUNCTION OF A FIRE INVESTIGATOR 10

11. DETERMINING CAUSE 11

12. FORENSIC SCIENCE II: ARSON AND FIRE INVESTIGATION, CHAPTER 4 © 2012 CENGAGE LEARNING. ALL RIGHTS RESERVED 12

13. INVERTED CONE PATTERN FORENSIC SCIENCE II: ARSON AND FIRE INVESTIGATION, CHAPTER 4 © 2012 CENGAGE LEARNING. ALL RIGHTS RESERVED 13

14. DETERMINING CAUSE 14

15. COLLECTING THE EVIDENCE  Begin immediately; no warrant required  Collect 3-4 liters of ash from point of origin and other suspected areas  Use portable vapor detectors, or sniffers  Use trained dogs to sniff 15

16. COLLECTING THE CONTROL  Place each sample in its own container  Collect a substrate control — a debris sample that has not been contaminated by the accelerant  Comparisons to the substrate control may help prove an accelerant was used  Some products may look like accelerants when burned 16

17. CRIME SCENE  What tests would you conduct?  What can you conclude from this picture? 17

18. FINDING THE IGNITER  Matches — often burns in the fire  Cigarette lighters — often removed by arsonist  Molotov cocktail — may leave glass fragments Molotov cocktail  Faulty electrical wiring — causes an arc which causes a predictable pattern  Knowing the igniter helps form the criminal profile 18

19. LAB ANALYSIS  Heat the debris container to collect vapors in the head space  1. Direct headspace extraction procedure  Remove vapors with a syringe  Analyze vapors with gas chromatography 19

20. LAB ANALYSIS  2. Passive headspace extraction procedure  Suspend a charcoal-coated strip inside the can  Replace lid  Heat container 4-16 hours at 50-80 o C  Charcoal absorbs the vapor 20

21. LAB ANALYSIS Passive headspace extraction procedure 21

22. LAB ANALYSIS  Separates hydrocarbon components  Most sensitive and reliable instrument for detecting and characterizing flammable residues 22

23. PSYCHOLOGY OF AN ARSONIST  Sense of power  An emotional high  No typical arsonist; possible characteristics: 23 Less than 25 years old Father not in the home Domineering mother Academically challenged Emotionally and/or psychologically disabled Unmarried Living with parents Inadequacy, insecurity Fascination with fire Alcoholism Parental neglect or abuse

24. MOTIVES FOR ARSON  Six categories: 24