Ethel Lillie Brown was born in 1892 in Lincolnshire, England, the daughter of a gamekeeper on the estate of Sir Henry Hawley. She grew up in a modest lodge house on the estate with her parents and three brothers. After leaving school at the age of 14, Ethel worked as a dressmaker. In 1915, she gave birth to a daughter named Auriol out of wedlock; to avoid scandal, her family raised Auriol as Ethel's sister rather than her daughter.​

In 1918, Ethel married Arthur Major, a World War I veteran who had been invalided out of service. The couple initially lived with Ethel's parents before moving to a council house in Kirkby-on-Bain, Lincolnshire, in 1929. They had a son, Lawrence, born in 1920. Their marriage became strained after Arthur discovered that Auriol was actually Ethel's daughter, not her sister. This revelation led to frequent arguments and a deteriorating relationship, with Ethel often returning to her parents' home to sleep.

On May 22, 1934, Arthur Major became violently ill after consuming a corned beef sandwich prepared by Ethel. Despite medical attention, his condition worsened, and he died two days later on May 24, 1934. Initially, his death was attributed to epilepsy. However, an anonymous letter to the police suggested that Ethel had poisoned Arthur, prompting an investigation. The letter also mentioned that a neighbor's dog had died after eating scraps from the Majors' household.​

An autopsy revealed that Arthur had died from strychnine poisoning. Tests on the deceased dog also confirmed the presence of strychnine. Ethel was arrested and charged with her husband's murder. During the trial at Lincoln Assizes, which began on October 29, 1934, the prosecution presented evidence of Ethel's access to strychnine through her father's locked box, to which she had a key. Witnesses testified about the troubled nature of the Majors' marriage and Ethel's alleged actions leading up to Arthur's death.​

Despite the defense's efforts, the jury found Ethel guilty on November 2, 1934, after deliberating for an hour. They recommended mercy, but the judge sentenced her to death. Appeals for clemency, including petitions and telegrams to the Home Secretary and the King, were unsuccessful. Ethel was executed by hanging at Hull Prison on December 19, 1934, becoming the only woman to be hanged at that facility.