Prefiguring the Arsenic Wars

David S. Caudill

A Striking Parallel

In January 2007 a jury in San Diego convicted Cynthia Sommer of murdering her husband, a marine sergeant, with arsenic. It was reported that she contacted an Internet dating service before her husband’s death, and that soon afterward she threw wild parties, had breast augmentation surgery, and began a new romantic relationship. These potentially irrelevant circumstances might have interfered with scientific investigation. On the basis of laboratory tests and expert opinions that seemed to prove that her husband died of arsenic poisoning, Sommer spent over two years in the Las Colinas jail. But when the verdict was challenged, sufficient questions were raised concerning the laboratory procedures and results to lead the prosecutor to send newly discovered tissue samples (preserved in paraffin) to the Quebec Toxicology Center. No arsenic was found in any of the samples, and tests determined that the earlier reported tissue distributions of arsenic were “physiologically improbable.” The murder charge was dropped.

The defense’s criticism of the prosecution’s experts and evidence repeated a pattern begun in the 19th century when arsenic-detection technologies were rapidly evolving: a toxicological expert was overly confident, the defendant was convicted, a more rigorous expert reanalyzed the evidence, and the defendant was acquitted. In the Sommer case it became clear that the initial specimens had been improperly transported and managed and that the government laboratory where they were tested lacked standard operating procedures and was not accredited by the American Board of Forensic Toxicology. The inexperienced analyst lacked the necessary knowledge to test for arsenic, and he rejected the possibility of sample contamination on the basis of an unscientific belief that a contaminating source can be monitored. In addition the lab did not follow a peer-reviewed arsenic speciation method and lacked appropriate chain-of-custody documentation for the specimens. Finally, the finding of 100% dimethylarsenic acid (DMA) was not consistent with other case studies involving death by inorganic arsenic, and Sommer’s husband did not display the appropriate symptoms before his death. As in the Logan case, the only explanation for such carelessness is in the unjustified overconfidence of the prosecution’s experts. In Jackson’s words, arsenic detection in the service of criminal law is a “life and death . . . business which the most experienced ought to approach with fear and trembling, with terror and dismay.”

Since the early 19th century, arsenic-poisoning trials have provided fodder for speculation on the moral character and salacious misdeeds of the accused—and of the scientists who accuse them. In the United States, France, Britain, and elsewhere accusations of hubris and moral carelessness have been as important in the advancement of science as in the advancement of justice. And, as the Sommer case makes clear, the arsenic wars have not ended. The dynamic changes in arsenic-detection techniques in the first half of the 19th century are similar to rapid developments in forensic science in the last several decades. The modesty and moral circumspection of some of the experts in chemistry just before and during the arsenic wars provide a model for the appropriate attitude toward forensic science in contemporary courts.

Detecting Arsenic

In 1836 English chemist James Marsh combined the previous work of Carl Wilhelm Scheele and Johann Daniel Metzger to form his revolutionary arsenic-detection process. Mateu Orfila famously employed the Marsh test in the highly publicized 1840 trial of Madame Lafarge, but there were many others who worked to find the perfect test for arsenic detection.

In the 1752 English trial of Mary Blandy, who was accused of poisoning her father, medical examiner Anthony Addington tested white powder found at the bottom of a pan that had been used to serve gruel to the victim.  Addington heated the powder and noticed the same garlicky smell as that of similarly tested arsenic.  In his 1803 book, Lectures on the Elements of Chemistry, Joseph Black described burning arsenic to yield whitish smoke and a garlic odor.  The 1806 book, Plain Discourses on the Elements of Chemistry by Thomas Ewell, also noted that arsenic powder placed on heated coals will produce white flames and a garlic smell.