Chemistry has been described as the central science because many other sciences arise from its principles. Biology is the study of life, and life is the result of complex chemical actions, reactions, and interactions. The scientific bridges linking chemistry and biology are biochemistry and molecular biology. These disciplines seek to understand how chemistry creates life and how life works at the level of chemical reactions. DNA (deoxyribonucleic acid), the molecule that carries genes and directs life, is a chemical compound. Because of its unique chemistry, DNA can self-replicate and control the production of cell proteins. In a modern forensic laboratory DNA typing is one of the principal tools used to study biological evidence.

Like all modern disciplines, chemistry has many subdisciplines and branches. Biochemistry is one, as are organic chemistry, inorganic chemistry, physical chemistry, and analytical chemistry, to name just a few. The American Chemical Society (ACS), the largest scientific society in the world, has more than 160,000 members, 19,000 of which are international and represent more than 100 countries. The ACS (available on the World Wide Web at publishes 36 journals and has nearly 200 local chapters and 33 technical divisions.

The first people to practice what would become chemistry were ancient physicians and pharmacists. They worked mostly with plants and devised teas, extracts, and other materials used to treat illness and injury. Their knowledge came from trial and error and was passed along by apprenticeship. By the time of the ancient Greeks the study of metallurgy had become important because of the value assigned to gold. If gold was to be fairly valued, the ancients realized, they needed a way to measure the purity of gold. Chemists were called on to analyze ores and coins to determine if gold was present, and if so, how much. This need led to the birth of analytical chemistry.

Chemestry Org Ore Com

Chemistry and forensic chemistry developed largely from ancient knowledge and techniques associated with medicines. This 4,000-year-old Sumerian clay tablet in the Museum of the University of Pennsylvania has been translated by Dr. Samuel Noah Kramer of the museum and by Dr. Martin Levey of Pennsylvania State College. The tablet contains the oldest-known medical handbook. A portion reads: "White pear tree, the flower of the 'moon' plant, grind into a powder, dissolve in beer, let the man drink." (Bettmann/CORBIS/ photo dated September 27,1953)

Analytical chemists investigate samples to understand their chemical content. This involves two tasks. First, the chemist must determine which chemicals are present, a process called qualitative analysis. A forensic toxicologist will test blood or urine to see what drugs or poisons might be present, while a forensic chemist working in a crime lab would first test a powder to determine what types of illegal drugs are present. The second step is quantitative analysis in which the amount or concentration of individual components is determined. Prior to the development of modern instrumentation, the painstaking process of analyzing a sample started with qualitative analysis, followed by a separate quantitative analysis of each of the components of interest. Often, accurate quantitative analysis was difficult or impossible. In modern forensic chemistry both steps can be accomplished at the same time, although multiple tests are used to ensure that the analysis is correct.

The application of chemistry to sample analysis is central to forensic chemistry. When a white powder is submitted to the lab, the question is always some form of "What is this?" and "How much is present?"


Forensic chemists are principally analytical chemists who apply their knowledge and expertise to samples linked to law enforcement or the legal system. Two divisions can be drawn within forensic chemistry. Those who analyze physical evidence such as powders, plant materials, and arson debris are usually referred to as forensic chemists, and they typically work in local, state, or federal crime laboratories. Forensic toxicologists work with drugs, poisons, and their biological by-products in blood and bodily fluids. They are employed in crime labs, medical examiners' offices, and a variety of other places. Other forensic chemists can be found working with trace and biological evidence, but their numbers are smaller.

Required education to enter the field of forensic chemistry includes extensive coursework in chemistry and biology. To work in local, state, or federal crime labs the entry-level education required is usually a bachelor of science degree (B.S.) in chemistry or a closely related natural science such as biology. Specific chemistry courses are required, such as introductory, organic, and analytical chemistry along with substantial laboratory work. Within a few years this minimum may increase to a master's of science degree (M.S.). For entry-level toxicology work, such as alcohol and drug screening, the requirements stress biochemistry and

A forensic chemist working with instrumentation in a forensic chemistry laboratory (Courtesy of the author)

related subjects. Many toxicologists have a Ph.D. in toxicology or pharmaceutical science.

Both forensic chemists and toxicologists work with drugs and poisons, but each starts with different evidence. A forensic chemist working in a crime laboratory would receive evidence such as plant material suspected of being marijuana or a white powder suspected of being cocaine. These samples are referred to as physical evidence. The chemist would use chemical tests to determine if the evidence is or contains an illegal drug. He or she would also be responsible for samples obtained from suspected arson crimes and might be called upon whenever samples come into the lab that would benefit from chemical analysis. Examples of this type of evidence include materials such as fire debris, soil, paint, glass, explosives, and fibers.

Toxicologists, on the other hand, work with biological evidence such as blood, saliva, urine, and feces. For example, when a person smokes the drug cocaine, that person's metabolism converts the cocaine to other substances that can be found in body fluids such as blood or urine. The toxicologist uses analytical chemistry to identify chemical traces and unmetabolized drugs. Toxicologists often work in labs associated with a medical examiner's (ME) office or a hospital. Unlike forensic chemists, forensic toxicologists usually do not deal with the drug or poison itself but rather biological samples that may contain it or its characteristic breakdown products. They follow the biological trail of a substance once it is ingested.

The field of forensic toxicology can be further broken down into more specific areas. The principal source of casework is usually blood alcohol determinations, in which toxicologists determine the percentage of ethanol present in a blood sample. These samples come from people suspected of drunk driving or related offenses and are often categorized as human performance toxicology. Forensic toxicologists also analyze samples taken as part of employment screening, both for governments and for private companies. Another branch of forensic toxicology is postmortem toxicology, where samples of blood and body fluids are obtained at autopsy.

Toxicologists can be involved in performance toxicology related to sporting events. At the Olympics a sophisticated laboratory is stationed close to the site to analyze samples taken from athletes to ensure that they are not taking banned substances. Many substances that are banned by sporting agencies are not illegal. Athletes are prohibited from taking them because they afford an unfair advantage over other competitors. For example, some antihistamines are banned in sports even though they are not illegal drugs. Sports samples are categorized as human performance toxicology, along with alcohol analysis. All of these substances (alcohol to steroids) affect performance, either by improving or by impairing it.


Drugs, Poisons, and Chemistry will touch on all aspects of what forensic chemistry was, how it developed, and what it includes today. The first chapter sets the stage through a short history of forensic chemistry: It begins with ancient physicians and pharmacists and moves quickly into the world of poisons. The most famous of these is arsenic. For thousands of years poisoning was the most feared of crimes and arsenic the most famous of poisons. More than any other substance this dull gray metal and its various forms gave birth to forensic chemistry and forensic science. The first chapter tells the story of arsenic and those who developed effective tests to detect it.

The second chapter delves into the tools and techniques used by forensic chemists. Some of these tools are familiar, such as the microscope, while others are less well known, such as the use of antibodies to detect toxins. One of the most important concepts in forensic chemistry is the study of color; this chapter will cover why color is important and how a forensic scientist uses and studies it. The following chapters cover the main areas of forensic chemistry: drug analysis and toxicology. The final chapter examines the state of forensic chemistry today and the trends that appear to be dictating its future. However, to understand where forensic chemistry is going, the place to start is where it began.

History and Pioneers

The history of forensic chemistry winds through the history of analytical chemistry, chemistry, and medicine. The ancient practices and beliefs of alchemy formed the basis of what would become the discipline of chemistry, from which forensic chemistry arose. Alchemy is often categorized as a diversion from science, but alchemy was science for more than a millennium. Alchemists such as Paracelsus, Robert Boyle, and Sir Isaac Newton made discoveries and developed techniques still used in forensic laboratories. Alchemy was the earliest form of analytical chemistry, which is the separation of compounds and elements from each other and from the matrix they are found in. For example, to determine the purity of gold it is necessary to analyze for the gold in a sample; to analyze for gold it is necessary to isolate the gold from any contaminants or adulterants found in it.

Most ancient cultures that left records practiced alchemy, which grew out of mining, metallurgy, and medicine. The undercurrent, even though the ancients did not recognize it, was chemistry. Alchemy was an odd and interesting blend of science, art, and religion that focused on the concept of purification and of separating material that was considered

"pure," such as gold, from the impure or whatever it was embedded in. Today's analytical chemist would call the gold the analyte and what it is embedded in the matrix. A forensic toxicologist testing urine for alcohol would call the urine the matrix and the alcohol the analyte. Analytical chemistry depends on the ability to isolate one or more components from a matrix.

The first mentions of alchemy date to around 400 b.c.e. The Greeks had the word chyma to describe processes of metalworking, and this might be one origin of alchemy, but the Chinese and Egyptians recorded similar words also related to metallurgy. All three cultures practiced alchemy, and the al part of the word appears to have come from Arabic,

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