Dating Victorian forensic science

In my Victorian mysteries, the question of poison occasionally arises. Most Victorian poisoning stories use arsenic, because it was everywhere. Yes, it was in rat poison, but also in face lotion (stronger than Clearasil), wallpaper, and fabric (a cool green was made from copper arsenic pigment*), and it was easy to obtain. Arsenic, I’ve learned, is a very slow poison. It’s perfect for killing your husband over six months and making it look like he died of natural causes. It’s not going to cause your victim to keel over as he’s drinking tea, which is what I wanted. But eventually my detective must figure out what happened, so the question is: what did they know about detecting poison in the 1860s?

A casual internet search suggests very little was known in the 1860s. Most sites say that the only poison that could be discovered post-mortem was arsenic. That’s because of the Marsh Test, famously created after Dr. Marsh’s frustration at having a clear sample that wasn’t long-lasting enough to show a jury.

Looking for information on forensic science, after Marsh, leads to the late 19th century (1880s and 90s) as the time when fingerprinting, chemical testing, blood analysis, etc. came onto the scene. The implication is that there wasn’t much going on until then.

And then I discover that Dr. William Guy, who appears as a character in my first mystery, was Professor of Forensic Science at King’s College, London. If the field was that new, it seems to me, there wouldn’t be that title. I was looking for books from the 1860s that might have forensics information in them, and I found two by Guy, both written in 1861: Principles of Forensic Medicine (2nd edition!) and On the Colour-Tests for Strychnia, from lectures he had given. Aha!

For me, the story of doing historical research has always been this: whatever you think was “invented” at a particular time, its actual invention and use was earlier. We tend to rely on patents, which may be years later. That’s why I prefer contemporary journals and medical texts instead. Primary sources may not be more accurate (they usually show one point of view, after all), but they are proof of ideas in circulation.

I only knew William Guy for his public health measures, so I am again pleased at how Victorian professionals could be involved in so many different aspects of their calling. Now, to see what’s motivating my poisoner…


*Wallpaper with arsenic could be used in children’s rooms, which sounds horrific until you realize that it was toxic to bedbugs and other critters that bite children. This doesn’t make it ok, just explicable.