Frances Knorr was born as Minnie Thwaites on December 10, 1868, in London, England. Her father was William Sutton Thwaites, a tailor from Chelsea. In 1887, she moved to Sydney in the Colony of New South Wales, seeking a new life.

In Sydney, she initially worked as a domestic servant. During this time, she met and married Rudolph Knorr, a German immigrant. Their marriage seemed stable at first, but eventually, Frances had an affair with a man named Edward Thompson.

The affair did not last long and left Frances in a difficult position. She moved to Melbourne to start over, but without much success. Struggling to support herself and her daughter, Frances had to find a way to make ends meet.

In February 1892, Victoria was going through a depression and jobs were hard to find. Rudolph Knorr, Frances's husband, was sent to prison for selling furniture he had bought on hire purchase. Frances, pregnant and without money, decided to start a child-minding business, which was really baby farming. She moved around Melbourne, often using both her maiden and married names.

Frances Knorr killed some of the babies she could not find homes for or sell to childless couples. While living on Moreland Road in Brunswick, she buried one baby in the garden. She buried two more at her next home on Davis Street.

The new tenant at the Moreland Road house found the body of a baby girl while working in the garden. The police traced the body back to Knorr, who had moved to Sydney with her husband. They dug up the gardens of other houses she had lived in and found the bodies of two boys at the Davis Street house. Sydney police arrested Frances on September 8.

Rudolph Knorr was also arrested but denied knowing about the burials. He was released the same day, as Melbourne police were not investigating him at that time. He said he had not seen Frances for 18 months until he moved back with her in Brunswick. They moved to Sydney six weeks before their arrest. He was arrested again the next day after new evidence connected him to the Davis Street murders.

During her interrogation, Frances remained cheerful but was upset by her husband's arrest. She insisted she was not guilty of murder. The police watched her closely, fearing she might try to escape. Shortly before her arrest, Frances had given birth to a daughter, Rita Daisy Knorr, who was taken into care.

Frances's trial began on November 27, 1893. She was charged with murdering the baby girl and, along with her husband, the two boys. The Crown prosecutor said Frances had the baby girl from April 8 to 11, after which the child was not seen again. Frances moved from Cardigan Street to Moreland Road on April 11 and borrowed a spade from a neighbor to dig in the garden. She moved again with Rudolph to Davis Street shortly after.

A letter from Frances to "Ted Thompson" was shown in court. It claimed the baby died of consumption and was buried by another man, but the letter was found to be a lie. Frances admitted to burying the babies but said they died naturally. The Crown proved they were strangled with a tape. Frances was found guilty and sentenced to death on December 15 by Justice Holroyd. She sobbed and collapsed during the sentencing. Rudolph was released on December 16 as the prosecution dropped further charges against him.

Public opinion was divided on Frances's sentence. Some letters to newspapers called for clemency. The state's hangman, Thomas Jones, committed suicide nine days before the execution after his wife threatened to leave him if he hanged Frances.

In prison, Frances was described as penitent and spent her time singing hymns and praying. She made a written confession before her execution, admitting guilt for the charges known as Number 1 and 2 babies. She hoped her confession would serve as a warning to others.

Frances Knorr was executed on January 15, 1894, at 10:00 am. She spent her last hours singing hymns. Her last words were, "Yes, the Lord is with me. I do not fear what men may do to me, for I have peace, perfect peace." She was hanged, and her death was recorded as instantaneous. Her death mask is displayed at the Old Melbourne Gaol.