"Chemical Evidence Stands for All Time"

Does it really? In actuality, matching the criminal with the crime isn't always that simple, despite what appears to be incontrovertible physical and chemical evidence.

But a hundred years ago criminologists thought they were on to something that could never be challenged in court. Article excerpts:

THAT WHILE the ordinary expert witness is given less and less credit by the average jury, the report of the professional chemist is regarded with increasing respect in court . . . Only within recent years, says Mr. [Daniel M.] Evosh, has the general public become familiar with the assistance given to the criminal inves-tigator by the chemist and microscopist. Almost every day the press contains reports of criminal trials or investigations in which the chemist plays an important part, and in the most celebrated cases of past years especial reliance has been placed on the evidence of the chemical analyst. — Unsigned,  "Chemistry and the Criminal," THE LITERARY DIGEST (September 7, 1912)

The funny thing about nature is that, while not intending to, it can fool you; but Mr. Evosh believed otherwise:

"The fiction writer of to-day gives the chemist a prominent part in the novels of the period. The refining touch of modern ideas and methods has turned the bludgeon into a hypodermic needle, the professional law-breaker into an individual of education, and makes the sleuth of the novel a person of high attainments and polish, a scientist, chemist, and psychologist.

"Sir A. Conan Doyle, himself a physician and chemist of high standing, as well as writer, novelist, and historian, in his portrayal of Sherlock Holmes realized the prominent part of the chemist in the investigation, detection, and conviction of the modern criminal, and many of his plots are laid in order to emphasize the absolutely certain and unimpeachable evidence revealed by the test-tube and microscope.

"Of all evidence given in a criminal case there is none so certain and final as chemical evidence. Even the eye-witness and the expert of any science may be controverted, but the evidence rendered by the chemist will always stand. The laws of chemistry are as certain and final as the laws of nature." — "Chemistry and the Criminal," op. cit.

If only that were true. Dr. Thorndyke shared Mr. Evosh's reverence for the scientific approach, but in the stories Thorndyke sometimes had to go to great lengths to connect the culprit with the crime, a process that would fail if any links in the chain were overlooked or destroyed. All claims for the infallibility of scientific criminal investigation must first allow for the all-too-real fallibility of the investigators.

Resource:
- For the pros and cons of what has come to be called "The CSI Effect," see this Wikipedia article.

Category: Detective fiction