Chapter 11: Arson And Explosives Section 1 Fire And Arson

Chapter 11arson And Explosivessection 1 Fire And Arsonthe Combustion

Chapter 11 arson and Explosives section 1: Fire and Arson The Combustion Reaction – Flaming and Glowing Combustions Investigating Suspicious Fires – Arsonists’ Motives Investigation of Fire Scenes Recovery of Ignitable Liquid Residues from Suspicious Fire Scenes Laboratory Analysis of Debris and Other Samples – Recovery of Ignitable Liquid Residues I. The Combustion Reaction Flaming and Glowing Combustion Combustion is a rapid oxidation reaction, the combination of fuel and oxygen to form carbon dioxide, water, and heat Chemical reactions that give off heat are called exothermic reactions Incomplete combustion reactions produce poisonous carbon monoxide I. The Combustion Reaction Flaming and Glowing Combustion 1. Necessary Components for Combustion: Combustion requires a number of components as shown by the fire triangle, tetrahedron, and pentagon The fire triangle shows the essential components as: fuel, oxygen, & heat The fire tetrahedron adds free radical reactions (chain reaction) The fire pentagon adds an ignition source I. The Combustion Reaction Flaming and Glowing Combustion There are two ways to interrupt a combustion reaction: adding water to absorb heat or adding fire retardants to interrupt the chain reaction process There are two major types of combustion: Flaming combustion - both the fuel and oxygen are in the gaseous phase Glowing combustion - the fuel is solid and only oxygen is in the gaseous phase I. The Combustion Reaction Flaming and Glowing Combustion 2. Nature of Fuels: Common fuels can be classified as solids, liquids or gases Gases – fuels include hydrogen gas, natural gas, methane, and propane Liquids – fuels include gasoline, fuel oil, kerosene, and ethanol Solids – fuels include wood, coal, charcoal I. The Combustion Reaction Flaming and Glowing Combustion 3. Characteristics of Fuels: Flash point – is the lowest temperature at which a liquid produces enough vapor to be ignited by a small flame Fire point (self - ignition temperature) – is the temperature at which there is enough heat to cause combustion even in the absence of a source of ignition Flammable Range – is a measure of the percentage of fuel that, when mixed with air, is needed to sustain combustion I. The Combustion Reaction Flaming and Glowing Combustion Relative Vapor Density – a property of compounds relating vapor density to molecular weight. Most materials when vaporized are much heavier than air Pyrolysis of Solid Fuels – the process by which solid materials are decomposed by heat, forming smaller molecules that can support flaming combustion II. Investigating Suspicious Fires Arsonists’ Motives There are several motives for most arson fires: economic, revenge, intimidation, and extortion Examples: Burning of buildings to collect on the artificially inflated insurance value Setting fire to a place in revenge or to teach the owner a “lesson” Setting fire to a business that refuses to pay for protection III. Investigation of Fire Scenes Fires are investigated to determine the cause of the fire and its origin 1. Burn Patterns: Since heat travels upward, pyrolysis occurs in materials above the area of combustion, producing a burn pattern that looks like an “inverted cone” or “V” pattern The inverted cone is a strong indicator that the point of origin of the fire lies at the point of the cone or base of the V Locating the point or points of origin is critical to the initial investigation of possible causes of the fire III. Investigation of Fire Scenes 2. Search for Causes: An important objective of the scene investigation is to determine the cause of the fire Determining the cause of a fire is basically a reconstruction Accidental causes include electrical short circuit, cooking accidents, and careless smoking IV. Recovery of Ignitable Liquid Residues from Suspicious Fire Scenes 1. Ignitable Liquid Residues: An ignitable liquid is one which can be ignited in the presence of air Ignitable liquids are not usually completely consumed in a fire as the liquids soak downwards while the fire burns upwards Ignitable liquids and accelerants are not completely interchangeable terms An accelerant is a flammable liquid or solid that may have been used to start or sustain a suspicious fire IV. Recovery of Ignitable Liquid Residues from Suspicious Fire Scenes 2. Searching for Places to Collect Debris: Residual ignitable liquids will most likely be found at or near the point(s) of origin Instruments “Sniffers”, can be used to detect hydrocarbon vapors and help to locate possible sources of ignitable liquids Dogs that are trained to detect the odor of common accelerants can also be used IV. Recovery of Ignitable Liquid Residues from Suspicious Fire Scenes 3. Collection & Packaging of Debris Samples: Samples should be collected from the point(s) of origin Fire debris samples must be packaged in airtight containers, such as clean metal cans Plastic bags may leak or be punctured IV. Recovery of Ignitable Liquid Residues from Suspicious Fire Scenes 4. Collection of Other Physical Evidence: Empty cans or containers at or near the scene may have trace amounts of liquid Ignition devices Fingerprints, footprints, toolmarks, blood etc. Ignitable liquid residues help to determine that the fire was intentionally set, but seldom helps to identify the arsonist V. Laboratory Analysis of Debris and Other Samples 1. Preparation of Liquid Samples: Liquid samples are simply drawn into a special syringe and injected into a gas chromatograph (GC) 2. Preparation of Fire Debris samples: There are four commonly used methods to separate or concentrate any ignitable liquids from fire debris samples: heated headspace, steam distillation, carbon strip or tube absorption, and solvent wash V. Laboratory Analysis of Debris and Other Samples i. Heated Headspace: The paint can containing the fire debris is punctured with a nail, the hole covered with tape, and the can incubated for 1+ hours at 70-80 °C After removing the can from the oven, the headspace vapor is quickly sampled with a gas-tight syringe and immediately injected into a GC Advantages: simple with minimal handling Disadvantages: not for trace amounts of ignitable liquid residues V. Laboratory Analysis of Debris and Other Samples ii. Steam Distillation: Debris is placed into a flask and either water or ethylene glycol added The flask is attached to a distillation apparatus and brought to a boil The condensate is collected, and if any ignitable fluids are present, it will separate into a second discernible liquid phase Disadvantages: time-consuming and risk of contamination V. Laboratory Analysis of Debris and Other Samples iii. Carbon Strip or Tube Absorption: Uses activated carbon to absorb hydrocarbon vapors A strip is suspended above the debris & the can is heated to vaporize the residues Hydrocarbons are removed from the strip by a solvent wash, which can be analyzed directly by GC A very sensitive technique V. Laboratory Analysis of Debris and Other Samples iv. Solvent Wash: Fire debris is placed into a flask, solvent added, mixed and allowed to sit for a period of time The solvent is separated from the debris, then analyzed as with the other approaches Works best for high boiling point ignitable liquids that cannot be easily vaporized V. Laboratory Analysis of Debris and Other Samples 3. Laboratory Examination of Prepared Samples: Gas chromatography separates mixtures of compounds by a partitioning process between a mobile and a stationary phase Ignitable fluids such as gasoline produce a very complex pattern of peaks V. Laboratory Analysis of Debris and Other Samples Different ignitable liquids will produce very different GC patterns A library of patterns is obtained from known standards of all possible accelerants With fire debris samples, many of the most volatile components tend to be lost The GC chromatograms can be compared to give an indication of the type of accelerant used, but the GC should not be considered an identification technique V. Laboratory Analysis of Debris and Other Samples Individual peaks from the GC can be identified using a mass spectrometer (MS) As compounds reach the end of the GC column, they pass into the MS The MS bombards the compounds with high energy electrons, fragmenting the compounds and yielding a mass spectrum that can be used to identify the compound Classification of Ignitable Liquids V. Laboratory Analysis of Debris and Other Samples Comparison specimens are samples of the surface or substratum on which ignitable liquid residues might be present Natural and synthetic materials may contain volatile compounds that produce GC peaks when heated or extracted Specimens should be collected from unburnt areas of the fire scene Arson and Explosives Section 2: Explosives & Explosion Incidents Characteristics of Explosives and Explosions The Three Major Classes of Explosives The Explosive Train or Device The Role of the Scene Investigator Laboratory Analysis of Explosives and Explosive Residues I. Characteristics of Explosives and Explosions An explosion is a very rapid chemical reaction that produces heat and gaseous products Explosions produce a large amount of heat (an exothermic reaction) in a very short time period Molecular fragmentation converts the solid explosive material into an enormous number of gas molecules which will occupy a much greater volume, further enhanced by the very high temperature of the explosion I. Characteristics of Explosives and Explosions The rapidly expanding gases compress the air creating a physical force known as a shock wave It is the shock wave that is responsible for much of the damage associated with an explosion II. The Three Major Classes of Explosives 1. Low Explosives: Low explosives are materials that burn rapidly and will only explode if contained Examples include smokeless powder and fireworks (pyrotechnics) Smokeless powders consist of nitrocellulose and black powder II. The Three Major Classes of Explosives 2. Primary High Explosives: Are used as primers or detonators Are sensitive to shock, heat, and electrical spark Examples include nitroglycerine, and mercury fulminate & lead styphnate which are used as primers in cartridges and blasting caps II. The Three Major Classes of Explosives 3. Secondary High Explosives: High explosives do not have to be contained to explode Are relatively stable and safe to handle Initiation requires an electrical spark, fuse, intense heat, or sharp blow Examples include dynamite, TNT, PETN, RDX, & ammonium nitrate III. The Explosive Train or Device The explosive train is the combination of components needed for a successful explosion (i.e. a bomb) An explosive device or train has three primary components: The igniter starts the event (e.g. a spark) The primer or detonator contains a primary high explosive (e.g. blasting cap) The main charge is a low explosive or secondary high explosive (e.g. dynamite) IV. The Role of the Scene Investigator The investigator must sort through all of the debris to find any portion of the explosive device and residue The debris is examined and any large pieces that do not appear to have been near the center of the explosion are removed The remaining debris is sifted through screens and examined for portions of the explosive device or items that show evidence of being close to the seat of the explosion Promising pieces are forwarded to the lab V. Laboratory Analysis of Explosives and Explosive Residues 1. Examination of an Unexploded Device: The device must first be rendered safe A detailed description is then made of each component and how they are connected to form the explosive train The chemical nature of the explosive ingredients is then determined, as an investigative lead and possible identification of the manufacturer V. Laboratory Analysis of Explosives and Explosive Residues 2. Examination of Exploded Devices & Debris The first step is the microscopic examination to locate small specks of explosive material as well as pieces of the original device If there is a lack of visible residue, selected pieces are washed with an organic solvent such as acetone, then subjected to chemical screening tests A second wash with water may be necessary to collect any inorganic residues V. Laboratory Analysis of Explosives and Explosive Residues 2. continued ... Chromatography is used to separate and clean components of interest for subsequent instrumental methods of analysis TLC or other chromatography methods are often used for this purpose Organic residues such as TNT are identified using IR spectroscopy or GC/MS Inorganic residues are examined using IR spectroscopy, X-ray diffraction or fluorescence V. Laboratory Analysis of Explosives and Explosive Residues 3. Examination of the Device or other Evidence Explosive devices are a combination of objects assembled in a particular way Examination of the type of wire, the timing devices, and the containment device can provide investigative leads Tool marks and fingerprints can be used to associate a person or workshop to a device The ProductionOfSpace0001.bmp TheProductionOfSpace0002.bmp TheProductionOfSpace0003.bmp TheProductionOfSpace0004.bmp TheProductionOfSpace0005.bmp TheProductionOfSpace0006.bmp TheProductionOfSpace0007.bmp TheProductionOfSpace0008.bmp TheProductionOfSpace0009.bmp TheProductionOfSpace0010.bmp TheProductionOfSpace0011.bmp TheProductionOfSpace0012.bmp TheProductionOfSpace0013.bmp TheProductionOfSpace0014.bmp TheProductionOfSpace0015.bmp TheProductionOfSpace0016.bmp TheProductionOfSpace0017.bmp TheProductionOfSpace0018.bmp TheProductionOfSpace0019.bmp TheProductionOfSpace0020.bmp TheProductionOfSpace0021.bmp TheProductionOfSpace0022.bmp TheProductionOfSpace0023.bmp TheProductionOfSpace0024.bmp TheProductionOfSpace0025.bmp TheProductionOfSpace0026.bmp TheProductionOfSpace0027.bmp TheProductionOfSpace0028.bmp TheProductionOfSpace0029.bmp TheProductionOfSpace0030.bmp TheProductionOfSpace0031.bmp TheProductionOfSpace0032.bmp TheProductionOfSpace0033.bmp TheProductionOfSpace0034.bmp TheProductionOfSpace0035.bmp TheProductionOfSpace0036.bmp TheProductionOfSpace0037.bmp TheProductionOfSpace0038.bmp TheProductionOfSpace0039.bmp TheProductionOfSpace0040.bmp TheProductionOfSpace0041.bmp TheProductionOfSpace0042.bmp TheProductionOfSpace0043.bmp TheProductionOfSpace0044.bmp TheProductionOfSpace0045.bmp TheProductionOfSpace0046.bmp TheProductionOfSpace0047.bmp TheProductionOfSpace0048.bmp TheProductionOfSpace0049.bmp TheProductionOfSpace0050.bmp TheProductionOfSpace0051.bmp TheProductionOfSpace0052.bmp TheProductionOfSpace0053.bmp TheProductionOfSpace0054.bmp TheProductionOfSpace0055.bmp TheProductionOfSpace0056.bmp TheProductionOfSpace0057.bmp TheProductionOfSpace0058.bmp TheProductionOfSpace0059.bmp TheProductionOfSpace0060.bmp TheProductionOfSpace0061.bmp TheProductionOfSpace0062.bmp TheProductionOfSpace0063.bmp TheProductionOfSpace0064.bmp TheProductionOfSpace0065.bmp TheProductionOfSpace0066.bmp TheProductionOfSpace0067.bmp TheProductionOfSpace0068.bmp TheProductionOfSpace0069.bmp TheProductionOfSpace0070.bmp TheProductionOfSpace0071.bmp TheProductionOfSpace0072.bmp TheProductionOfSpace0073.bmp TheProductionOfSpace0074.bmp TheProductionOfSpace0075.bmp TheProductionOfSpace0076.bmp TheProductionOfSpace0077.bmp TheProductionOfSpace0078.bmp TheProductionOfSpace0079.bmp TheProductionOfSpace0080.bmp TheProductionOfSpace0081.bmp TheProductionOfSpace0082.bmp TheProductionOfSpace0083.bmp TheProductionOfSpace0084.bmp TheProductionOfSpace0085.bmp TheProductionOfSpace0086.bmp TheProductionOfSpace0087.bmp TheProductionOfSpace0088.bmp TheProductionOfSpace0089.bmp TheProductionOfSpace0090.bmp TheProductionOfSpace0091.bmp TheProductionOfSpace0092.bmp TheProductionOfSpace0093.bmp TheProductionOfSpace0094.bmp The Community College of Baltimore County The School of Justice CRIMINALISTICS CRJU 112 Module 11: Arson and Explosions Module Introduction This module explores the forensic aspects of arson and explosion investigation including the chemistry of fire, searching fire scenes, collecting and preserving arson evidence, types of explosives, and the collection and analysis of explosion evidence. Learning Objectives After completing this module you will be familiar with the following learning objectives: You will be able to: 1. Explain the science underlying combustion (fire) 2. Describe useful information available from careful examination of a fire scene 3. List the primary reasons for individuals setting arson fires. 4. Describe the proper examination and processing of materials collected in the investigation of suspicious fires. 5. Summarize the processes involved in laboratory analyses of arson evidence. 6. List the most commonly encountered ignitable liquids used as accelerants in arson fires. 7. Explain the science underlying an explosion. 8. Describe the requisite components of an explosive device. 9. Describe laboratory procedures in the analyses of explosive devices and residues. 10. Explain how explosives are identified from the analysis of explosive residues. Learning Activities To successfully complete this module, you should complete the following learning activities: · Read Chapter 11 (pp. ). · Review the Power Points for Chapter 11. · Complete the following writing assignments: A.) Answer the following Review Questions (short answer) on page 308 (worth up to 10 points): 1, 2, 3, 4, and 5. B.) Answer the Fill-in-the-Blank & Multiple-choice Questions 1 through 5 on page 308 (worth up to 10 points). SUBMISSION INSTRUCTIONS: Submit your work as instructed in previous modules.

Paper For Above instruction

Arson and explosions present complex challenges to forensic investigators, requiring a deep understanding of fire chemistry, scene analysis, and explosive materials. This paper explores the scientific principles underlying combustion and explosion phenomena, methods for investigating suspicious fires, collecting physical evidence, laboratory analysis techniques, and the identification of accelerants and explosive residues. Emphasizing a scientific approach enhances the accuracy and reliability of forensic conclusions, which are critical for effective criminal prosecution and justice.

Introduction to Fire and Arson Investigation

Fire investigation begins with understanding the fundamental chemistry of combustion. Combustion is a rapid oxidation process involving fuel, oxygen, and heat, resulting in the formation of gases, heat, and light (Bain, 2012). The fire triangle—comprising fuel, oxygen, and heat—is the simplest model for understanding the necessary components for fire. More advanced models such as the fire tetrahedron add the role of free radicals, which propagate the chain reactions critical to sustaining a fire (Jackson & Carter, 2015). The fire pentagon further recognizes the importance of an ignition source. Interrupting combustion can be achieved by removing any of these elements, for example, by applying water to absorb heat or fire retardants to disrupt chain reactions (Cernoch et al., 2017). Different fuel types—solid, liquid, or gaseous—have distinct combustion properties. Gases like methane and propane ignite readily, while solids such as wood or coal require pyrolysis to decompose into combustible gases (Fisher et al., 2019).

Science of Combustion and Fuel Characteristics

Understanding fuel properties is essential for fire scene analysis. The flash point defines the lowest temperature at which