Abstract
Arsonists usually use accelerants to speed up combustion when they set something on fire. The most commonly used accelerants include gasoline, paraffin, turpentine, acetone, and isopropyl alcohol. During investigations, investigations must begin by identifying the origin of a fire. The origin could contain evidence of accelerants used. Methods used to identify accelerants include human olfactory testing, photo-ionization detectors, flame ionization detectors, fast chromatography, and accelerant canine detector. Collecting quality samples is important. Therefore, investigators should establish a crime scene perimeter to prevent any destruction of evidence.
Introduction
One of the techniques used by investigators for determining whether a fire is incendiary is to check for the presence of accelerants. This is conducted using several techniques. An accelerant is any substance that hastens the process of combustion. Evidence of accelerants is the main type of physical evidence that issued to prove arson.
Where to Look for Evidence of Accelerant Use
The most commonly used accelerants in arson include petroleum, kerosene, turpentine, gasoline, acetone, and isopropyl alcohol. An important aspect of arson investigation is the determination of the origin of fire (Schottke, 2012). My investigation partner should also look for evidence of accelerant use at the origin of the fire. The origin of the fire usually contains residues of the accelerant used in the arson (Almirall & Furton, 2016). After the origin of the fire is identified, then the next task is to look for the presence of accelerants. I would instruct my partner to start looking for evidence in the garage and kitchen because these areas were the origins of the fire. Therefore, I would ask him to look for evidence of accelerants on floors and carpets. These are the best places to look for evidence because liquid accelerants run to the lowest level when poured. Also, these areas usually have the lowest concentrations of oxygen due to low temperatures (Almirall & Furton, 2016). Therefore, the accelerant that flows to these areas usually does not burn completely. It is important also for the partner to look for evidence of accelerants on the clothes and shoes of the suspect if he/she is apprehended. Adsorbent materials such as clothes and wood could have evidence of accelerants (Michelson, 2015).
Detection for Accelerants
Some several methods and techniques are used to detect the presence of accelerants. They include mechanical and electronic equipment, human olfactory testing, photo-ionization detectors, flame ionization detectors, fast chromatography, and chemical color test (Hess, Orthmann, & Cho, 2016). Human olfactory testing is one of the most widely used techniques. This method involves the smelling of fire debris to detect any odor of accelerants that have characteristic odors (Wright & Singer, 2014). This method is cheap and highly effective. However, it becomes ineffective after prolonged periods of exposure to chemicals. Mechanical and electronic equipment are classified into four groups namely, flame ionization detectors, catalytic combustion detectors, semiconductor-based instruments, and photo-ionization detectors (Avery, Byram, D., Davis, Michelson, & Starrett, 2015). The main advantage of using catalytic combustion detectors is that they are calibrated to prevent trace hydrocarbons from interfering with their sensitivity. The calibrations on these devices usually correspond to concentrations of specific flammable gases (Wright & Singer, 2014).
I would use photo-ionization detectors because they are highly sensitive and highly selective for hydrocarbon vapors. Also, they are small and portable, the ad allows rapid sampling in a crime scene. High sensitivity implies that the chances of concluding are very low (Avery et al., 2015). I would also use fast gas chromatography because it detects and analyzes accelerants faster than typical analytical techniques. Finally, I would sue accelerant detection canines. Flame ionization detectors measure the degree of ionization after mixing sample vapor with gaseous hydrogen (Wright & Singer, 2014). The ionization degree determines the conductivity of the gas mixture, which produces a reading that indicates the presence of accelerants. Finally, I would use accelerant detection canines (ADC). An accelerant detection canine is a specially-trained dog used during arson investigations to sniff minute traces of accelerants (Avery et al., 2015). I would use dogs because their sense of smell is more acute than that of human beings and they are fast in sniffing a fire scene. Besides, they are more accurate when compared to the use of human olfactory senses. Human olfactory testing usually leads to a collection of approximately 20 different samples. In contrast, an ADC narrows down the testing and leads to the collection of three samples on average.
Crime Scene Perimeter
The main purpose of establishing a crime scene perimeter is to restrict access to the area and prevent any possible interference with or destruction of evidence (Michelson, 2015). In many cases, the scene is secured with a barrier, tape, or rope. The best crime scene perimeter to establish would be the entire house because evidence of arson could be at any location in the house. Also, it could be necessary to establish a 30-meter perimeter around the house. The arsonists could have left physical evidence that could be useful in apprehending them.
References
Almirall, J. R., & Furton, K. G. (2016). Analysis and interpretation of fire science evidence. New York, NY: CRC Press.
Avery, T., Byram, D., Davis, A., Michelson, R., & Starrett, P. (2015). Homeland security principles, planning & procedures. New York, NY: LawTech Publishing Group.
Hess, K. M., Orthmann, C. H., & Cho, H. L. (2016). Criminal investigation. New York, NY: Cengage Learning.
Michelson, R. (2015). Criminal investigation: Introduction to concepts and applications. New York, NY: LawTech Publishing Group.
Schottke, D. (2012). Fundamentals of fire fighter skills. New York, NY: Jones & Bartlett Publishers.
Wright, J. D., & Singer, J. (2014). Fire and explosives. New York, NY: Routledge.