Nellie May Madison, born Nellie Mooney on April 5, 1895, in Beaverhead County, Montana, was raised in the small town of Dillon. Her early years were marked by rugged self-reliance; she was trained from a young age to survive in the mountainous terrain of Montana. Her upbringing instilled in her a fiercely independent spirit and a toughness that would later define her personality and decisions.

Madison's personal life was complex and tumultuous. At the age of 13, she was involved in a short-lived relationship that led to an annulled marriage to a 23-year-old ex-convict. Over the years, she entered into and subsequently ended several marriages—reportedly at least five prior to her final marriage in later life. Despite multiple marriages, she had no children. Nellie worked various jobs and traveled frequently, demonstrating an independent streak uncommon for women in the early 20th century. She was known to be strong-willed and assertive, traits that often set her apart from traditional expectations of femininity during her time.

Before her fateful marriage to Erik Madison, little is recorded about her criminal background, suggesting she lived largely within the law. Her marriage to Erik would, however, prove deeply toxic and would eventually culminate in the crime that would make her infamous in California legal history. At the time of the murder, Nellie was living with Erik in Burbank, California. Their marriage was reportedly plagued by violence, infidelity, and manipulation—issues that became central to her legal battle.

On March 24, 1934, Nellie May Madison shot and killed her husband, Erik Madison, in their home in Burbank, California. According to her later statements and supporters, the killing occurred after prolonged episodes of physical abuse and threats. On the night of the incident, Erik was allegedly in the process of undressing when Nellie confronted him with a gun. When he reached under the bed for a box of butcher knives and allegedly threatened to "cut her heart out," she opened fire. Erik was shot five times in the back and died at the scene.

Following the killing, Nellie Madison was arrested on March 25, 1934, and charged with first-degree murder. During her trial, prosecutors painted her as a calculating and cold-blooded killer. The lead prosecutor was Los Angeles County District Attorney Buron Fitts. On the advice of her defense team, Nellie initially denied being present at the scene and did not disclose the abuse she endured, a decision that backfired when her alibi was deemed implausible. The jury convicted her of first-degree murder in June 1934, and Judge Charles Fricke sentenced her to death by hanging, making her the first woman in California history to receive a death sentence.

Her conviction sparked immediate controversy. As new evidence and public interest emerged, particularly through the efforts of journalist Agness "Aggie" Underwood, it was revealed that Erik Madison had a history of domestic abuse. He had coerced both Nellie and a former wife into signing false confessions of infidelity, while he was known to have had affairs with underage girls. This new understanding reframed the case in the public eye. Nellie’s ex-husband, still a friend, encouraged her to come forward with the truth about the abuse.

A groundswell of public support followed. All members of the original jury that convicted her signed a petition to spare her life. In September 1935, Governor Frank Merriam commuted her death sentence to life imprisonment. During her incarceration, Nellie launched a letter-writing campaign pleading for clemency. Eventually, California Governor Culbert Olson ordered her release on March 27, 1943—exactly nine years and three days after the murder.

Nellie quietly rebuilt her life after prison. She moved to San Bernardino and married her sixth and final husband, John Wagner, a house painter. The marriage lasted until her death. Nellie May Madison died of a stroke on July 8, 1953, at the age of 58.