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Forensic Science | 7.1 Arson and Explosives Assignment Your certification exam is coming up next week to renew your credentials as an Arson and Explosives expert. Your supervisor has implied that you may be up for a promotion upon attaining a superior score on the certification exam. You would love a promotion with a new title and salary, so you created a study guide for yourself for the concepts you need to focus on the most for the exam. Complete the study guide below so that you are ready for anything the exam throws at you! In each of the scenarios listed below, answer the analysis questions. (1 point each unless noted) Scenario 1 At the scene of a house fire, you observe the following characteristics: ● More than one point of origin ● Ribbon shaped fire patterns from the point of origin ● “Alligator skin” crackling patterns on walls and floor ● Melted glass ● Buckled Steel beams ● Matchbook found in bushes near house ● Burned, but recognizable gas can be found near a back door 1. Are these characteristics indicative of a natural fire, accidental fire, or arson? They are indicative characteristics of arson. 2. Explain how EACH of the characteristics above indicate the type of fire you identified in #1. If there is more than one point of origin then it means that the acceleration was lit at many parts of the crime scene, showing intention. The ribbon shaped fire patterns from the point of origin indicate that the fire was following a line of accelerant, meaning it was put there. The “alligator skin” crackling patterns on the walls and floors show that that is where the fire was the hottest. The melted glass and buckled steel beams tell us that there was an accelerant there that made those materials melt. The matchbook found in the bushes near the house indicate that it could have been used as the accelerant. The burned gas can near the back door, indicated that the gas was the accelerant, leading to the conclusion of arson. 3. Why is it important to have a person specifically trained in arson to investigate the scene if arson is suspected? It is important to have a person specifically trained in arson to investigate the scene if arson is suspected, because they are trained to look for certain patterns and evidence. 4. What is the proper procedure for collecting suspected arson evidence? When collecting suspected arson evidence, you want to first locate the point of origin, and then try to locate the accelerant or ignition device. After both are located, then any ash, soot or other materials are collected and put into airtight containers. There are also metal paint cans that can help transport the evidence to the lab. It is important that the container is airtight so that if there is residue on the evidence it can still be collected. 5. How is a piece of charred wood tested for the presence or accelerants? © Copyright Michigan Virtual 2020 Revised 4/22/2020 Page 1
A piece of charred wood is tested for the presence of accelerants by warming the can to release any accelerants. The vapors left over are then tested using gas chromatography and mass spectrometry. These tests will show the mixture that was inside the vapor. 6. How sensitive is this method? This method is sensitive because it can detect amounts of accelerant as small as 1/1000 of a drop. 7. Name and describe the three parts of the fire triangle. The 3 parts of the fire triangle are oxygen, fuel, and heat. Oxygen should be enough to contain combustion, fuel is any sort of flammable fuel, and heat is used to make the fuel source ignite. 8. Name 3 common accelerants used in arson. Three common accelerants used in arson are kerosene, diesel fuel, and gasoline. 9. Research and report here about 1 famous arson case. Give a brief summary of the case details. (2 points) In the fall of 1973, Evelyn Wagler, 24 years old, separated from her husband and child and moved from Chicago and Boston. On October 2, Evelyn was two blocks away from her home when her car ran out of gas. She decided to walk in the opposite direction to the gas station, and she filled up a can of gas and carried it to her car. WWWHen she was walking home there were six teenagers in an alley who dragged and forced her to pour gasoline on herself. The teenagers then lit a match and set Evelyn on fire then ran away. Evelyn was taken to the hospital, but died a few hours later. Before she had died she told police that three of her attackers had recently told her to move out of the neighborhood. At the time there was a movie where people were burnt alive with gasoline, and many thought that this is where the plan sprouted from. The six teenagers who burned Evelyn Wagler were never found. Scenario 2 (10 points) You are called to the scene of an explosion on the 4 th of July. You observe the following characteristics: ● The area where the explosion occurred is extensively damaged. ● Windows shattered in nearby homes by flying debris. ● A debris pile that appears to contain multiple nails and screws. ● Shrapnel and screws lodged in the wood siding of a nearby home. ● Witnesses reported hearing a very loud explosive sound at the time of the explosion. It was reportedly much louder than anything they had heard before. ● The remains of what appears to be a mangled and badly damaged metal briefcase are found near the explosion site. ● A second similar, undamaged briefcase is found a short distance from the location of the original explosion. 1. Do you feel that this explosion was due to fireworks, a drug lab explosion, gas main leak, or a bomb? What clues lead you to this conclusion? I feel that this explosion was caused by a bomb. The clues that led me to this conclusion were the extensive damage, the presence of nails and screws, shrapnel, the loud explosive sound, and the mangle metal briefcase. 2. What is the first step that must be done before anyone enters the explosion site? The first step that must be done before anyone enters the explosion site is to ensure that the area is secure and safe from potential hazards like secondary explosions, or structural instability. 3. Is this characteristic of a low or high explosive? These characteristics are indicative that it was a high explosion due to the damage caused and the presence of shrapnel and nails. © Copyright Michigan Virtual 2020 Revised 4/22/2020 Page 2
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