Crime Solving With Chemistry

The widespread popularity of both factual and fictional television drama based on forensic science has resulted in a tremendous interest from the general public on how science is applied to solving crimes and, in particular, how chemistry tools are used in the forensic laboratory. The new, aptly titled book “Crime Scene Chemistry for the Armchair Sleuth by Cathy Cobb, Monty L. Fetterolf, and Jack G. Goldsmith, is aimed at this general audience of adults with little or no previous background in chemistry. The light, informative, and often humorous book hits the mark on several levels and should also be of interest to the more chemistry savvy readers of Chemical & Engineering News.

The book is divided into four parts, with the first part providing a basic background to chemical principles over eight chapters and introducing such topics as uncertainty in measurements, atomic structure, and the notion of presumptive chemical testing of drugs, for example. Part two contains nine chapters and raises the level of chemistry principles covering topics such as rates of chemical reactions, chemical equilibrium, and acid-base chemistry. Part three contains four chapters focusing on spectroscopy and the tools available to forensic chemists for compound identification, such as infrared analysis of fibers to determine the polymer type class. Part four concludes the book with four chapters devoted to the analysis of biological samples such as fingerprints, body fluids, and DNA.

All 25 chapters begin with a laboratory demonstration intended to illustrate the main point of the chapter. All the demonstrations are designed to be conducted using readily available household materials or easily obtainable items. The list of necessary materials is given at the beginning of the book and broken down into several categories to facilitate their acquisition. Readers are free to select the items they would need for the sections of the book of most interest. Each chapter also contains a fictional vignette describing a crime scene “case” related to the demonstration and is followed by a more theoretical description of the chemistry behind the case. Each chapter then concludes with a “case solved” section returning to the vignette, complete with dialogue between officers and/or scientific personnel.

The vignettes are fictional and include dialogue between fictional characters, so the book reads more like an episode of the TV drama “CSI: Las Vegas” rather than the also popular and fact-based TV program “Forensic Files.” One of the authors, Goldsmith, is both a chemist and a reserve police officer, which explains the ample police jargon used throughout the book. The reader is taken from the world of law enforcement to the world of science and back in every chapter, always ending in the successful resolution of “the case.”

The book’s first chapter, “Confidence in Chemistry and Confidence in Clues: The Significance of Digits,” uses a simple description of the difference between presumptive chemical tests and confirmatory tests to introduce the subject of uncertainty in measurements. For the laboratory exercise, the reader is asked to use kitchen measuring cups to perform a set of measurements and gain an appreciation for the inherent uncertainty of measurements and to illustrate the need for calibration of instruments.

The laboratory exercise in chapter 2 demonstrates how minute particles of drugs can be detected on currency. White acetaminophen powder is introduced to a bill and then removed so it is not visible to the naked eye. The exercise demonstrates the sensitivity of chemical tests with the detection of very small quantities of drugs, in this case, acetaminophen. The chapter continues with an introduction to atomic theory and describes the confirmatory tests used to prove the presence of drugs on currency. It also discusses the use of isotope profiling to determine the provenance of drugs, a technique actually used by law enforcement for intelligence purposes. The authors do, however, exaggerate the value of isotope profiling.

Chapter 4 covers the topic of separation sciences in drug analysis using a paper chromatography demonstration as an aid to the case description. Chapter 6 introduces the concept of mass spectrometry in the case example and with an exercise that illustrates the relationship between an electric field and a magnetic field. The authors then go on to provide an explanation of how a gas chromatograph mass spectrometer operates to separate and identify drugs. Chapter 7 describes the steps in a death investigation resulting from a drug overdose using the notion of concentration differences and dosage effects on the body. The demonstration and case description in chapter 8 introduces the concept of the use of microcrystalline tests for the identification of chemical compounds, a technique that is still widely used in forensic laboratories today.

Chapters 9 and 10 describe the differences between physical and chemical changes, and chapter 11 further uses acid-base chemistry to explain the conversion from the salt form of cocaine to the freebase “crack” form. The use of gunshot residue (GSR) analysis can provide evidence that a person has recently fired a weapon, and chapter 13 describes the process for the detection of GSR particles.

Chapter 16 introduces the concept of density gradients for the analysis and comparison of soils to determine whether two soil samples could have a common origin, a technique still used by forensic laboratories. The next chapter describes the use of chemical extractions within the process of forensic examinations of unknowns, as it is often the case that police investigators will request investigative leads from fragments of materials found at crime scenes.

Most viewers of the “CSI” television series are generally impressed with the capabilities of the advanced chemical instrumentation used in forensic laboratories. The chapters in part three provide a good background description of how spectroscopy can be used for compound identification, in particular how infrared analysis can be used to identify the polymer type of fibers, even when only a single microscopic fiber is available for analysis. This section also covers the use of optics and the microscope and includes a basic description of the scanning electron microscope, another common tool in the forensic laboratory. Finally, the section includes a description of the more “sexy” tools in the forensic laboratory such as laser ablation for the analysis of paint chips in chapter 20, which details the investigation of a hit-and-run accident.

Arguably, the most significant advance in forensic science over the past 25 years has been the unambiguous identification of people through DNA (when a comparison sample is available). Biological evidence such as the smallest amount of blood, for example, can place a suspect at a crime scene. Chapter 24 covers the topic of DNA analysis with some detail including a description of the difference between mitochondrial and nuclear DNA. Finally, the authors provide their view of the future of crime scene investigation. For example, they predict the use of chemical sniffers sensitive enough to provide clues as to what has happened at the scene of a crime and how to focus an investigation on the basis of those results. This scenario hinges on chemical evidence that we know is readily available but today is not yet accessible for analysis and interpretation.

This book will satisfy the curiosity of the “CSI” television series fan who wants to learn more about how chemistry is used to solve crimes both in the forensic laboratory and at crime scenes. Additionally, it offers the possibility for the adventurous reader to partake in kitchen chemistry exercises, including various relevant demonstrations on the approach to forensic tools. The authors’ light approach to crime scene investigation makes for easy reading.

For the scientist and nonscientist alike who are interested in how the fascinating world of chemistry has a socially relevant application, but with a healthy dose of reality, reading the book and taking part in the demonstrations will benefit them. The book also leads to a deeper understanding of the forensic toolbox, including the capabilities and limitations of some of the tools. This kind of understanding of the merits of scientific evidence is something we all need when sitting in the jurors’ box tasked with deciding the guilt or innocence of someone charged with criminal wrongdoing.