Crime Library: Criminal Minds and Methods

Forensic Toxicology

The Next Step

Another major step in the history of forensic toxicology was the development of methods during the 19th century for detecting the presence of vegetable alkaloids, such as caffeine, quinine, morphine, strychnine, atropine, and opium.   Plant alkaloids leave no demonstrable traces in the human body, thus requiring relatively complicated methods of extraction before an analysis can be performed.  These poisons affect the central nervous system.  Even Orfila had no success and he thought that the isolation of alkaloids from human tissues might be altogether impossible. 

Jean Servois Stas, portrait
Jean Servois Stas, portrait

His student, Jean Servois Stas, had a different idea.   In a murder trial in 1850, the male victim showed clear chemical burns in his mouth, tongue, and throat.  Stas searched for three months for the agent, and eventually managed to isolate nicotine from the body tissues.  Using ether as a solvent, which he then evaporated to isolate the drug, he found the potent drug.  It was, in fact, the murder weapon.  The man's killer had extracted it from tobacco and force-fed it to the victim.  With Stas's testimony, the killer was convicted.

Stas thus became the first person to develop a method to extract the material containing the plant alkaloids from the organic material of the human body, and for many years thereafter, with some modifications, it was used as the standard.   Other toxicologists then developed qualitative tests with the Stas procedure to determine the presence of various alkaloids in the obtained extract.

A case in which this method played a significant role was the murder of the young French widow, Madame de Pauw.   Her alleged murderer was a homeopathic doctor, Couty de la Pommerais, who was her lover.  Pommerais was in financial trouble at the time, and de Pauw had a large life insurance policy of which Pommerais was the beneficiary.  One day, de Pauw mysteriously fell ill and died within hours.  An anonymous note alerted the police to foul play. 

The forensic pathologist, Professor Ambroise Tardieu, suspected from the victim's odd symptoms—especially her racing heart--that Pommerais had used the paralyzing drug, digitalin.   To demonstrate the presence of digitalin in Madame de Pauw's body, Tardieu injected several frogs with the extract he had obtained using the Stas method, as well as with a standard solution of digitalin.  The reactions from those frogs injected with the standard and those injected with the extract were exactly the same.  This evidence held up in court and on June 9, 1864, Pommerais was convicted of murder and executed.   

Yet there was also a problem with these tests: false reactions.   At times, an alkaloid might develop in the body after death that mimicked the reactions of the qualitative color tests for the vegetable alkaloids.  These substances are known as "cadaveric alkaloids."  In order for the toxicologists to be certain that they were identifying a poison correctly, they needed a method that was specific only to that vegetable alkaloid, or they had to run a number of tests and obtain positive reactions to all of them.  This discovery of cadaveric alkaloids created a need for new tests to be developed.

An important case that involved cadaveric alkaloids was that of the murder of Annie Sutherland.   Sutherland owned a saloon which her alleged murderer Buchanan frequented.  Eventually Buchanan and Sutherland married; however, Buchanan was having financial troubles at the time.  When Sutherland mysteriously died, he was heir to all of her assets, and therefore had a motive to kill her.  Toxicologists determined that Sutherland died of morphine poisoning, although she did not display the determining characteristic of narrowed pupils.  It was discovered that Buchanan had put drops of atropine in her eyes to dilate them and foil the doctors.  The toxicological evidence seemed overwhelming, but on the stand, Professor Victor Vaughn proved the existence of a cadaveric alkaloid that mimicked morphine in all of the known morphine qualitative tests.  This cast a shadow of doubt on all of the toxicological evidence.  In the end, based on his own self-incriminating testimony, Buchanan was convicted in 1895, but the jury did not take the toxicological evidence into consideration.

This forensic fiasco inspired toxicologists to look for new methods of demonstrating the presence of alkaloids in the body—so a setback became a means for improvement.   Dr. William Henry Willcox was the first to propagate the idea of using the melting point and crystallization patterns of the alkaloid as an identifier.  However, even this method had its problems, as some alkaloids proved to have similar melting points.  Thus, melting point and crystallization then could only be used in combination with other qualitative tests.  More and better tests were developed, and by 1955, there were 30 tests for morphine alone.

Another problem for the toxicologist in the second quarter of the 20th century were synthetic alkaloids, developed with the growth of pharmaceutical chemistry, which required entirely new methods of separation from the body extract and a different means of identification.   One of the responses to this problem came from A.S. Curry.  He proposed the use of column, or paper, chromatography as a means of separation based on molecular size or polarity.  It makes colorless alkaloids visible and easily separated onto filter paper.

This was a good thing, because with industrialization, poisons of all types were becoming available to millions in the form of cleansers, medicines, and pesticides, and their many variations were multiplying.