Mary Blandy, Arsenic Poisoner

This week, I’m reaching way back to 1751 for a murder by arsenic poisoning. This is a classic English case of the use of “inheritance powder.” Unfortunately for her, the poisoner, Mary Blandy, didn’t get away with it.

Setting the Scene

Mary Blandy was a young woman living at home with her father, Francis Blandy, an attorney in Henley-on-Thames. Mary was 26 in 1746, which in those days would have put her well into spinsterhood. However, that year, she met Captain William Henry Cranstoun, a Scottish military officer. The two planned to marry in 1751.

Mary Blandy, Arsenic Poisoner
Mary Blandy, Arsenic Poisoner (Public Domain)

There was just one problem. Cranstoun already had a wife and child in Scotland, having married Anne Murray the year before he met Mary.

Francis Blandy approved of his daughter’s proposed marriage—that is, until he learned about the wife in Scotland. Consequently, he forbade Mary to see Cranstoun. Cranstoun, for his part, claimed that his marriage to Murray was invalid. He even made several trips to Scotland to have his marriage annulled. But Anne was having none of it and Cranstoun was unable to obtain the annulment.

Poisoning Francis Blandy

Francis Blandy died on August 14, 1751 as a result of what authorities determined was arsenic poisoning. Servants had noticed a white powder in the bottom of a pan Mary had used to prepare her father’s food and saved a sample of it. So, naturally, Mary Blandy came under suspicion. But did she intend to murder her father?

Mary claimed that Cranstoun had sent her a “love potion” that she was to put into Francis’s food to make him approve the of her relationship with Cranstoun. Mary put the “potion” in Francis’s food. Of course, the “potion” turned out to be arsenic.

Mary Blandy on Trial

Mary went on trial at Oxford on March 3, 1752. Her trial was notable for being the first murder trial to include scientific evidence. Her father’s physician, Anthony Addington, testified that the powder given to Francis Blandy was arsenic. Addington proved the powder was arsenic by heating it and detecting arsine gas, which has the odor of garlic. (A more precise test for arsenic was decades in the future.)

Bottle of Arsenic
Vintage arsenic poison bottle on antique shelf

Mary presented the love potion story in her defense, but other facts brought out during the trial contradicted her. Not surprisingly, the jury convicted her.

Mary Blandy was hanged outside Oxford Castle Prison on April 6, 1752. Her last words were purportedly, “Do not hang me too high, for the sake of decency.”

Cranstoun fled to France and thereby escaped prosecution, but he died soon after on December 2, 1752.

How Guilty Was Mary?

Mary admitted feeding the “love potion” to her father, so there is little question of her technical guilt. But was she morally guilty? Was she simply a lovesick woman who believed her lover’s story of a “love potion?” Or were she and he more interested in the £10,000 dowry the elder Blandy had promised? The debate continued for several years. At the time, few people accepted her story on the witness stand, as most believed she was lying. Nineteenth century reexaminations of her case were more sympathetic to the “poor, lovesick girl” view.

Mary Blanchard had a reputation as a well-educated young woman, so I find it difficult to believe she could swallow the “love potion” story. I think it is more likely that she knew what she was doing. Mary may or may not have poisoned her father for love, but I believe Cranstoun’s motivation was the £10,000. However, more than two and a half centuries after the fact, determining the exact truth presents a challenge.

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