Celestina Sommer was born on July 1, 1827, in Islington, a borough in north London. She was the fourth of eight children in her family. Her family were silversmiths, which was considered a respectable profession at the time. Celestina showed talent in music from an early age. She became an accomplished pianist and music teacher. She regularly performed at a well-known venue called St Martin's Hall at Covent Garden. This was part of John Hullah's popular school of music.

When Celestina was 18 years old, in 1845, she had a daughter out of wedlock. She named her daughter Celestina as well. However, during the Victorian era, being an unmarried mother came with many hardships and social stigma. Because of this, Celestina gave her daughter to a foster family named Thomas and Julia Harrington.

In 1854, Celestina married Charles (Karl) Sommer. He was an immigrant from Prussia and worked in the metalwork and jewelry industry. It is possible that he worked with Celestina's father. Celestina and Charles were married at St Mary's, Islington Parish Church in Middlesex. After their marriage, they lived in Charles' house in an area that had been redeveloped into what is now known as the Packington Estate.

On February 16, 1856, Celestina Sommer collected her estranged daughter from her foster parent in Hackney. They returned to the Sommer residence, where Celestina attacked her daughter in the front cellar and cut her throat. The maid, Rachel Munt, was sleeping in the kitchen nearby and heard the event. The next day, Munt managed to raise the alarm without alerting Celestina. By 4:30 PM on February 17, both Celestina and her husband Charles were arrested on suspicion of murder. They were taken to Hoxton police station by Inspector Edward Hutton and Sergeant Edwin Townsend.

Later, two hearings were held at Clerkenwell Police Court. The magistrate identified the deceased girl as Celestina's daughter and incorrectly assumed a motive for the killing. Charles was released after denying any involvement, as he had been absent during the murder and did not know the child.

The coroner's inquest took place at the North Pole Inn in Islington. The jury ruled Celestina complicit in her daughter's death. Meanwhile, Rachel Munt faced danger from an angry mob as she returned home but was rescued by police officers.

Celestina appeared at the Central Criminal Court, Old Bailey, on March 7 and again on April 10. During her second trial, she was found guilty of willful murder after the jury deliberated for only 15 minutes. Celestina exhibited signs of distress during the proceedings. Justice Crompton pronounced her sentence to be death.

At the time, there was no clear agreement on what constituted insanity. Celestina's defense did not enter a formal plea of insanity. However, there was growing support for her case, with many claiming she was mentally unstable when the crime occurred. Prominent figures, including Alfred Dymond, advocated for her.

Despite the outrage over her crime, Sir George Grey commuted her death sentence to transportation and then to life imprisonment. This decision faced major criticism as her reprieve came just as she was due to be executed. The reasons for his decision were never disclosed, leading to public outcry.

The case received worldwide attention, with debates about crime, the death penalty, and gender fairness in the legal system. Sommer remained a figure of controversy, with many believing she escaped justice due to her gender and appearance.

Following her sentencing, Celestina endured years in the British penal system. Her mental health declined while in various prisons, culminating in her transfer to Fisherton House Lunatic Asylum. She died on April 11, 1859, at the age of 31. An examination revealed health issues consistent with brain damage, but many believed she had escaped true accountability.