Marie Jeanneret was born on January 13, 1836, in Le Locle, Switzerland. She grew up in a small Swiss town known for its watchmaking. Little is known about her childhood and family life. However, she became a nurse as an adult. This profession allowed her to gain knowledge about medicine and treatments, which would later play a role in her life.

Jeanneret had a strong interest in medicine and pharmacology. Her nursing career gave her access to various medicines and poisons. This knowledge set her apart from many others in her community. Her interest in how these substances affected people was evident as she conducted her own experiments.

Marie Jeanneret was a Swiss serial killer active between late October 1867 and mid-January 1868. She was accused of murdering six people and poisoning three others during this time. Her method was to use poison, specifically atropine and morphine. On November 23, 1868, she was formally charged with these crimes.

During her trial, Jeanneret admitted to administering the poisons but claimed she did so out of medical curiosity. She wanted to understand the effects of the substances, not to kill. However, the court found her guilty. The President of the Court was Eugène Colladon, and the public prosecutor was William Turrettini. Her defense lawyer was Gaspard Zurlinden.

Although she was found guilty, the jury determined there were extenuating circumstances. As a result, she received a sentence of twenty years in prison, which was the maximum penalty available. This case was significant in that it led to changes in the legal system; the death penalty was abolished in the canton of Geneva in 1871, following public advocacy by politician Marc Héridier. Marie Jeanneret died in prison on April 4, 1884.