Amy Archer-Giligan from Windsor, Connecticut is considered the most prolific female serial killer, with a possible victim count of 60 of the residents in her nursing home for the elderly. That’s how many residents died between the years of 1907 to 1917. However, not all of them were confirmed. After a relatively healthy resident died suddenly of “stomach ulcers,” as it first appeared, suspicion fell on Archer-Gilligan from the victim’s sister and subsequently local authorities. They exhumed the body and performed an autopsy that showed that the victim, Franklin R. Andrews, died of arsenic poisoning.
So, during this time period, arsenic was readily available as it was frequently used as a rat killer. The only catch was that you did have to sign documents when you purchased the substance. Authorities easily found that Archer-Gilligan was buying entirely too much arsenic to just be killing rats. So, they exhumed four more previous residents of Archer-Gilligan’s and found large amounts of arsenic in their bodies as well. That put the charges against her at five. However, her lawyer managed to get it down to just the murder of Andrews. She was sentenced to death in 1917. However, she appealed and was granted another trial in 1919 but was still found guilty. This time, they sentenced her to life in prison. In 1924, they transferred her to the Connecticut Hospital for the Ins*ne in Middletown and she stayed there until she died in 1962.
The reason this is classified as “unsolved” is because we will never know the number of victims she really had, with only five confirmed. They would have had to exhume every single one of her previous residents that had died and, as stated earlier, that number was 60. They had enough to convict on the five they did confirm and that was all they were concerned with.