She claimed that she thought the arsenic was a love potion that would make her father approve of her relationship with William Henry Cranstoun, an army officer and son of a Scottish nobleman.

[1] After months of stalling, Mary's father, Francis Blandy, became suspicious of Cranstoun and believed that he did not intend to leave his wife.

Mary claimed that Cranstoun sent her a love potion (which later turned out to be arsenic) and asked her to place it in her father's food to make him approve of their relationship.

[1] The trial on 3 March 1752 was of some forensic interest, as there was expert testimony about the arsenic poisoning that was presented by Dr. Anthony Addington.

On Easter Monday, 6 April 1752, Blandy was hanged outside Oxford Castle prison for the crime of parricide.

In the nineteenth century, her case was re-examined in several texts with a more sympathetic light, and people began to think of her as a "poor lovesick girl".