Sickle
Forensic analysis of criminal activity has been around for a long time. The first written account of using forensic techniques to solve a murder occurred in China around approximately 1248. The written account by Song Ci describes an investigation of a murder case in which the victim was killed by wounds delivered by a sickle. A sickle is a bladed instrument generally used to cut wheat or other grains. The death investigator compared the wounds on the victim to wounds he created on animals using several different bladed instruments until he found the match to the sickle. He then instructed everyone to bring their sickle to one location. Flies, attracted by the smell of blood, eventually gathered on the murderer's sickle evoking a confession. Song Ci also wrote instructions on how to distinguish between a drowning (water in the lungs) and strangulation (broken neck cartilage). He also determined by examining corpses methods for determining if a death was caused by murder, suicide or an accident.
Early forensics and crime-solving chemists - Deborah Blum
TED-Ed (YouTube)
While the use of flies does not seem to be a reliable method for determining the identity of a murderer this was better than the more common method of the time – eye witness accounts and testimony. Unfortunately, it is not until many centuries later that the first chemical investigative techniques were introduced. One of the first chemicals to be investigated in relation to murder was arsenic. As little as 70 mg may be fatal to an adult and arsenic poisoning has been suspected as the cause of death in many famous murders. In 1587 the entire Medici noble family was poisoned by arsenic most likely by the Duke’s brother, Ferdinand. Napoleon Bonaparte and Simon Bolivar, both dictators of some ill-repute, are thought to have died from exposure to arsenic although the exposure may have been environmental not criminal. Arsenic was a favored poison as it was generally undetectable until the late 1700's.
As2O3 + 6 Zn + 6 H2SO4 → 2 AsH3 + 6 ZnSO4 + 3 H2O
Zn = Zinc metal, H2SO4 = Sulfuric Acid, AsH3 = Arsine gas
The process of developing a test to determine the presence of Arsenic in a victim took many years and several dedicated chemists. The resulting test, called the Marsh Test is shown here. The sample suspected of containing Arsenic is treated with Zinc (Zn) and Sulfuric Acid (H2SO4). If even minute traces of arsenic are present, Arsine gas forms and can be collected. If known amounts of arsenic are tested the same way, a correlation (calibration graph) between the concentration of arsenic in a sample and the arsine gas formed can make the quantitative determination of the arsenic present possible.
Arsenic
adriana salazar (YouTube)
The timeline for development of the Marsh test is one of the earliest developments of a chemical test specifically for investigative purposes.
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Carl Scheele 1775As2O3 + 6 Zn + 12 HNO3 → 2 AsH3 + 6 Zn(NO3)2 + 3 H2O
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Johann Metzger 17872 As2O3 + 3 C → 3 CO2 + 4 As
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Valentine Rose 1806K2CO3, CaO and HNO3
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James Marsh 1832Loses murder case
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James Marsh 1836Develops the Marsh Test
In 1775 Carl Scheele, a prolific chemical experimentalist, discovered that if he reacted arsenic oxide (As2O3) with zinc (Zn) and nitric acid (HNO3), a garlic smelling gas would form. Soon after, in about 1787, Johann Metzger developed a process that created an arsenic mirror from the same arsenic oxide compound. In 1806, Dr. Valentine Rose would be the first to use these two prior discoveries to determine whether a patient of his had died from arsenic poisoning. Dr. Rose took the stomach and its contents from the victim and cut them up and boiled them to release any chemicals bound in the flesh. After filtering the concoction, he treated it first with nitric acid and then with Metzger's technique to confirm the presence of arsenic. In 1832, as the world continued to sophisticate, James Marsh attempted to use the same techniques to convince a jury that a man had murdered his grandfather by arsenic poisoning. Although Metzger's test was capable of indicating the presence of arsenic it was not well developed enough to determine the amount of arsenic quantitatively and Marsh was unable to convince the jury of the man's guilt. Based on this failure, Marsh returned to his lab and through a number of experiments developed the Marsh Test which with some additional refinements is still used today.
Detecting Arsenic - The Marsh-Test
Chaoschemiker (YouTube)
Many further techniques began to form during the 19th century. In 1839 toxicological evidence was used for the first time in a criminal trial. 1863 the first presumptive test for blood was discovered and although you might not think immediately think of it as a chemical process in this digital age, the development of photographs during the mid-1800's allowed for better preservation of crime scene evidence and the people involved. It should be noted that the first fascination with criminalistics began in the late 19th century as a result of two events – the reign of terror caused by Jack the Ripper who is thought to have killed at least 5 women during the year 1888, and the publication of the Sherlock Holmes novels by the author Sir Arthur Conan Doyle. Both brought the crime and the investigation that followed to the attention of the general public in a manner never seen before. Based on the success of shows like CSI and Bones as well as older shows like Quincy, M.E. and your presence in this course, the fascination continues today.