Doss finally confessed to the murders in October 1954, after her fifth husband had died in a small hospital in Tulsa, Oklahoma. In all, it was revealed that she had killed four husbands, two children, her two sisters, her mother, a grandson, and a mother-in-law.
Nannie was born on November 4, 1905 in Blue Mountain, Alabama, now part of Anniston, as Nancy Hazel to Louisa "Lou" (née Holder) and James F. Hazel. Nannie was one of five children; she had one brother and three sisters. Both Nannie and her mother hated James, who was a controlling father and husband. James would force his children to work on the family farm instead of attending school, resulting in Nannie's poor academic performance. At age 7, while the family was taking a train to visit relatives in southern Alabama, Nannie hit her head on a metal bar on the seat in front of her when the train suddenly stopped. For years after, she suffered severe headaches, blackouts and depression; she blamed these and her mental instability on that accident. During childhood, her favorite hobby was reading her mother's romance magazines and dreaming of her own romantic future. Later, her favorite part was the lonely hearts column. Nannie's father forbade the Hazel sisters from wearing makeup and attractive clothing to prevent them from being molested by men. However, that happened on several occasions. He also forbade them to go to dances and other social events.
Nannie was first married at age 16 to Charley Braggs, her co-worker at a linen factory. With her father's approval they married after four months of dating. Braggs was the only son of a single mother who insisted on continuing to live with him after he married. Nannie later wrote:
I married, as my father wished, in 1921 to a boy I only knowed about four or five months who had no family, only a mother who was unwed and who had taken over my life completely when we were married. She never seen anything wrong with what he done, but she would take spells. She would not let my own mother stay all night...
Braggs' mother took up a lot of his attention and limited Nannie's activities. The marriage produced four daughters from 1923 to 1927. The stressed-out Nannie started drinking, and her casual smoking habit became a heavy addiction. Both unhappy partners suspected each other, correctly, of infidelity, and Braggs often disappeared for days on end.
In 1923, the couple lost their first two girls to suspected food poisoning. Suspecting that Nannie had killed them. After 1926, Braggs took firstborn daughter Florine and fled, leaving newborn Melvina behind. Soon after, Braggs' mother died and Nannie took a job in a cotton mill to support Melvina and herself. Braggs brought Florine back in the summer of 1928, accompanied by a divorcée with her own child. Braggs and Nannie soon divorced, with Nannie taking her two girls back to her mother's home. Braggs always maintained he left her because he was frightened of her.
Living and working in Anniston, Nannie soothed her loneliness by reading romance magazines and novels. She also resumed poring over the lonely hearts column, and wrote to men advertising there. A particular advert that interested her was that of Robert Franklin "Frank" Harrelson, a 23-year-old factory worker from Jacksonville. He sent her romantic poetry, and she sent him a cake. They met and married in 1929, when she was 24, two years after her divorce from Braggs. They lived together in Jacksonville with Melvina and Florine. After a few months, she discovered that he was an alcoholic and had a criminal record for assault. Despite this, the marriage lasted 16 years.
Melvina gave birth to Robert Lee Haynes in 1943. Another baby followed two years later but died soon afterward. Exhausted from labor and groggy from ether, Melvina thought she saw her visiting mother stick a hatpin into the baby's head. When she asked her husband and sister for clarification, they said Nannie had told them the baby was dead—and they noticed that she was holding a pin. The doctors, however, couldn't give a positive explanation. The grieving parents drifted apart and Melvina started dating a soldier. Nannie disapproved of him, and while Melvina was visiting her father after a particularly nasty fight with her mother, her son Robert died mysteriously under Nannie's care on July 7, 1945. The death was diagnosed as asphyxia from unknown causes, and two months later Nannie collected the $500 life insurance she had taken out on Robert.
In 1945, Japan surrendered to the Allied powers at the end of World War II, and Harrelson was among the most robust partiers. After an evening of particularly heavy drinking, he raped Nannie. The next day, she discovered Harrelson's corn whiskey jar buried in the ground as she tended her rose garden. The rape had been the last straw for her, so she took the jar and topped it off with rat poison. Harrelson died a painful death that evening.
Nannie met her third husband, Arlie Lanning, through another lonely-hearts column while travelling in Lexington, North Carolina, and married him three days later. Like Harrelson, Lanning was an alcoholic womanizer. However, in this marriage it was Nannie who often disappeared—and for months on end. But when she was home, she played the doting housewife, and when he died of what was said to be heart failure, the townspeople supported her at his funeral. Soon after, the couple's house, which had been left to Lanning's sister, burned down. The insurance money went to Nannie, who quickly banked it, and after Lanning's mother died in her sleep, Nannie left North Carolina and ended up at her sister Dovie's home. Dovie was bedridden; soon after Nannie's arrival, she died.
Looking for yet another husband, Nannie joined a dating service called the Diamond Circle Club and soon met Richard L. Morton of Jamestown, North Carolina. He didn't have a drinking problem, but he was a womanizer. Morton met his death on May 19, 1953. Nannie's mother Lou had come to live with them and also died by poison.
Nannie married Samuel Doss of Tulsa, Oklahoma, in June 1953. Doss was a Nazarene minister who had lost his family to a tornado in Madison County, Arkansas. Samuel disapproved of the romance novels and stories that his wife adored. In September, Samuel was admitted to the hospital with flu-like symptoms. The hospital diagnosed a severe digestive tract infection. He was treated and released on October 5. Nannie killed him that evening in her rush to collect the two life insurance policies she had taken out on him. This sudden death alerted his doctor, who ordered an autopsy. The autopsy revealed a huge amount of arsenic in his system. Doss was promptly arrested.
Doss confessed to killing four of her husbands, her mother, her sister, her grandson, and her mother-in-law. The state of Oklahoma centered its case only on Samuel Doss. Nannie Doss was prosecuted by J. Howard Edmondson, who would later become governor of Oklahoma. She pleaded guilty on May 17, 1955, and was sentenced to life imprisonment; the state did not pursue the death penalty due to her gender. Doss was never charged with the other deaths. Doss died from leukemia in the hospital ward of the Oklahoma State Penitentiary in 1965.