Minnie Dean was born Williamina McCulloch in Greenock, Scotland, on 1 September 1844 into an upper working class family. Her father John McCulloch was an engine driver. The family lost three infant daughters and the mother, Lizzie (neé Swan), died of cancer in 1857 after a prolonged illness. Minnie’s father remarried two years later, to another Lizzie. (Minnie’s older sister was also called Lizzie.) By 1861, Minnie was no longer living at home.

In 1863, Minnie arrived in Invercargill, New Zealand, at the home of her maternal aunt, Christina (née Swan), known locally as Granny Kelly, who, with her husband, was one of the first settlers of Invercargill. There is no formal record of Minnie between these dates. It is thought she may have been in Tasmania. She arrived in New Zealand with one young daughter, Ellen, and pregnant with another (Isabella).

Minnie worked as a governess and school teacher, with the support of Aunt Christina, until she married Charles Dean in 1872. No record has been discovered of her having been previously married as she claimed. The marriage of Minnie and Charles was childless and they adopted Margaret Cameron around 1880. The year before, Ellen had married a landowner farmer, and in 1882 seemingly drowned her infants and herself in their well.

The financial circumstances of Charles and Minnie took a downturn from early in the marriage, until in 1884 when Charles became bankrupt and Minnie responsible for making ends meet. Conveniently, the law changed in New Zealand in 1884 with the passage of The Married Women’s Property Act, and Minnie expanded her business of caring for and sometimes adopting, unwanted children. She adopted Esther Wallis to assist her with the infants and young children. Minnie soon became labelled as a ‘baby-farmer’, attracting the attention of the local policeman, Constable Hans Peter Rasmussen. Deaths and disappearances of some young children in her care increased concern, although inquests cast no suspicion upon her. Deaths of infants and young children were commonplace in Victorian times, even in intact caring families, and reached over 90% for infants placed in institutional care.

Eventually, after police discovered the bodies of two recently deceased infants and a skeleton in the garden at their home, Minnie Dean and Charles Dean were arrested on 9 May 1895. The charges against Charles were subsequently withdrawn. Further inquests followed and a magisterial hearing, then on 18 June 1895 the trial of Minnie Dean commenced in the Invercargill Supreme Court before Mr Justice Joshua Strange Williams. There was wide newspaper coverage of both the inquests and the trial and these provide the most complete record of proceedings. Minnie was convicted and sentenced to death five days later.

The appeal was unsuccessful, as was the plea for clemency from the then Governor George Grey, and Minnie Dean was executed in Invercargill Prison on 12 August 1895, the first and last woman hanged in New Zealand.