Forensic Crime Research Paper

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FORENSIC CHEMISTRY
David Collins Brigham Young University—Idaho

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rime-time television is chock-full of drama centered on the criminal justice system. Programs such as CSI: Crime Scene Investigation, Law & Order, Criminal Minds, and Cold Case carry the viewer through stimulating, yet nearly impossible-to-solve, investigations that culminate with the evidence revealing the entire untold story behind a crime in one hour or less. In real life the collection and analysis of evidence involves painstaking care and rigorous application of scientific principles. Have you ever wondered how evidence in an actual case tells the story, what information each item of evidence holds, and how this information
Figure 1 illustrates the role that each of these individuals plays in an investigation. Although the service provided by the forensic scientist is central to the solving of many crimes, it is not usually required for crimes like speeding or shoplifting. In fact, most crimes do not require a forensic analysis of physical evidence. Physical evidence present at a crime scene may not even be collected; and if it is collected, it may not be analyzed. The decision to collect and subsequently analyze physical evidence depends on the seriousness of the crime, police department protocol, the state of the investigation, laboratory capabilities, and crime scene resources. A large number of forensic scientists are chemists. Forensic chemists employ their knowledge of chemistry to analyze evidence such as fibers, paint, explosives, charred debris, drugs, glass, soil, documents, tool marks, and firearms. To a lesser extent, forensic chemists also use their knowledge for toxicology (the study of poisons and their effects), fingerprints, footwear impressions, tire impressions, and hair analyses. Although many forensic analyses require the expertise of a chemist, chemistry is not the only discipline that contributes to the extremely vast and truly interdisciplinary field of forensic science. Other disciplines and professions contributing to the field include engineering, computer science, entomology, anthropology, pathology,
For example, if a white powder is submitted for analysis, the primary objective will be to determine its identity. If the powder is suspected of being a controlled substance, the forensic scientist will carry out a series of analyses to identify the powder. However, because each drug has a different set of physical and chemical properties, a different series of analyses is required to identify each drug. As mentioned during our discussion of the scientific method, the forensic scientist must first make an educated guess as to the identity of the substance. Using known drug standards for each type of drug to be analyzed, she must develop and validate a series of analyses prior to analyzing the questioned samples. Consequently, the identification of an uncommon drug can be challenging. Two types of analysis can be used to identify the substance: presumptive and confirmatory. Presumptive analyses look at chemical and physical properties that are not unique enough by themselves for identification but that provide enough information to narrow the search. For example, the forensic scientist may guess that the questioned sample is methamphetamine. A known chemical property of methamphetamine is that it will react with sodium nitroprusside in the presence of sodium bicarbonate and produce a very deep bluecolored product, so the scientist will carry out this test. If the reaction