Neighbors called her the "West Auckland Poisoner" long before police caught on. By the time they exhumed her stepson's body, she'd already buried three husbands, a lover, her own mother, and most of her thirteen children.
Mary Ann Cotton, born Mary Ann Robson in 1832, is believed to be Britain's most prolific serial killer, convicted and hanged in 1873 for poisoning her stepson with arsenic. She's suspected of killing as many as 21 people over roughly two decades.
A Pattern That Began Young
Cotton grew up in County Durham, the daughter of a coal miner who died in a mining accident when she was young. She trained briefly as a nurse before marrying colliery labourer William Mowbray in 1852. Over the following years, the couple had eight or nine children, most of whom died young of what was recorded at the time as gastric fever — a pattern that would repeat itself across four marriages and three decades. William himself died in 1865, leaving Cotton a life insurance payout equivalent to roughly half a year's wages.
Marriage After Marriage
Cotton remarried repeatedly in the years that followed, and death followed each new household. A second husband died within months of their marriage. Her mother died suddenly in 1866 while Cotton was staying with her. A third husband, James Robinson, grew suspicious after Cotton repeatedly pressed him to take out a life insurance policy and after several of his children from a previous marriage died shortly after Cotton moved in; he was the only husband to survive his marriage to her, after she left him in 1869. In 1870, she moved in with widower Frederick Cotton, whose surname she took, though the marriage was technically invalid since she'd never legally divorced Robinson.
The Beginning of the End
In 1871, Cotton, her husband Frederick, his two sons, and her own infant daughter moved into a home in County Durham. Within about a year, Frederick, the baby, a former lover named Joseph Nattrass who had moved in as a lodger, and one of Frederick's sons had all died. When Cotton tried to have Frederick's remaining son, Charles Edward Cotton, sent to a workhouse and was refused, she told a parish official she wouldn't be troubled by him much longer. Days later, the boy was dead.
Arsenic Found
A doctor who had treated Charles had kept tissue samples, which tested positive for arsenic. Police exhumed his body and confirmed the poisoning, then exhumed the bodies of Nattrass and two of the Cotton children, all of which also showed signs of arsenic poisoning. Cotton was arrested and charged with Charles's murder.
Trial
Cotton's trial began at Durham Assizes in March 1873, delayed until after she gave birth to her thirteenth child in prison. Prosecutors presented evidence of her arsenic purchases and the long trail of deaths that had followed her for years; her defense argued Charles may have inhaled arsenic dust from the home's green wallpaper dye, a common household hazard at the time. The judge dismissed the theory, and after just 90 minutes of deliberation, the jury found her guilty.
A Botched Execution
Mary Ann Cotton was hanged at Durham County Gaol on March 24, 1873. The execution was mishandled — the drop wasn't long enough to break her neck cleanly, and she was left to slowly strangle, taking roughly three minutes to die while the executioner pressed down on her shoulders to hasten it.
A Legacy That Outlived Her
Of Cotton's thirteen children, only two survived her. She maintained her innocence to the end, and her case became notorious enough to inspire a Victorian-era children's rhyme still occasionally referenced today. She was the subject of a 2015 ITV drama, "Dark Angel," starring Joanne Froggatt.
Frequently Asked Questions
How many people did Mary Ann Cotton actually kill?
She was convicted of only one murder, that of her stepson Charles, but is suspected of killing as many as 21 people, including 11 of her 13 children and three of her four husbands.
Was Mary Ann Cotton really Britain's first female serial killer?
She's often described that way, though earlier cases exist; she's widely regarded as Britain's most prolific female serial killer until Harold Shipman's case a century later.
Did Mary Ann Cotton ever confess?
No. She maintained her innocence throughout her trial and up until her execution.