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Connecting the Dots: The Science of CSI

Chemistry

Toxicology

At the turn of the 20th century, the average household’s cleaning supplies and health and beauty products often contained deadly chemicals. Insect spray had potassium cyanide; skin treatments contained thallium; creams to soothe teething babies had morphine; and radioactive radium was everywhere from cosmetics to watches and therapeutic tonics. These products were readily available to consumers and packages often had no warning labels and or ingredient lists. The easy availability of these toxins also made them perfect murder weapons.

The science to understand and detect dangerous poisons lagged, and police departments lacked chemistry labs to investigate the increase in suspicious deaths. In 1918, Charles Norris, Chief Medical Examiner of New York City, decided to take action. His first hire was chemist Alexander Gettler, who teamed with Norris to create the country’s first forensic toxicology laboratory. Gettler, known today as the “father of forensic chemistry,” estimated that he investigated over 100,000 deaths during his career.

Dr. Alexander Gettler (left) in his laboratory with Dr. Charles Norris

Dr. Alexander Gettler (left) in his laboratory with Dr. Charles Norris. Image courtesy of the Library of Congress.

Traité de Toxicologie

Mathieu Orfila was the first scientist to combine forensic and clinical toxicology with analytical chemistry. In 1813, while demonstrating an arsenic test to his students, he discovered the test did not perform as advertised. He then began to test and re-test all known procedures for detecting other poisons. He published the results of these experiments in 1814 with the first edition of Traité de toxicologie. The book went through several editions and became the benchmark of modern forensic toxicology.

Image of the first edition of Traité de toxicologie

Image source: Orfila, Matthieu. Traité de toxicologie. 5th ed., Labé, 1852. View Source

The Marsh Test

In the early 19th century, arsenic was a favorite poison of murderers. It was quick acting, nearly impossible to detect, and its symptoms resembled cholera and dysentery. In 1836, English chemist James Marsh created the first reliable test for arsenic. It involved heating material suspected of containing arsenic in a glass tube (a) containing zinc and sulphuric acid. The resulting gas was released through an open stopcock (b). If arsenic was present, it collected on a piece of glass (f) held above the tube. The test was so sensitive it could detect one-fiftieth of a milligram of arsenic. The Marsh Test became a standard forensic procedure and is the fundamental basis for tests used today.

Illustration of the Marsh Test used to test arsenic

Image source: Marsh, James. “Method of Separating Small Quantities of Arsenic.” Edinburgh New Philosophical Journal, vol. 21, no. 42, 1836, pp. 229-236. View Source