John Tawell (1784–1845) was a British murderer. He was the first person to be arrested as the result of telecommunications technology.
Transported to Australia in 1814 for the crime of forgery, Tawell obtained a ticket of leave, and started as a chemist in Sydney. There he flourished, and some years later left it a rich man.
Returning to England, he married a Quaker woman as his second wife. In 1845 he was convicted of the murder of his mistress, Sarah Hart, by administering prussic acid, his apparent motive being a dread of their relationship becoming known.
Tawell started out as a shop worker in London and for some years worked in a number of businesses owned by the strict religious society, the Quakers, which he later joined. He was later disowned by the Quakers as a result of his relationship with a non-Quaker woman, Mary Freeman, whom he ultimately married and with whom he had two children.
In 1814 Tawell was charged with possessing forged banknotes from the Uxbridge Bank, potentially a capital offence. However, the Quaker-owned Bank was opposed to the death penalty and, mindful of scandal, negotiated for Tawell to be allowed to plead guilty to a lesser offence. The result was that his sentence was commuted to fourteen years transportation to the penal colony of Sydney. After eventually obtaining his ticket of leave, Tawell prospered, opening the colony's first pharmacy and conducting numerous property and business ventures. His family rejoined him in Sydney in 1823 and Tawell set about rehabilitating his reputation, being influential in setting up the first Quaker community in Australia and engaging in various philanthropic activities.
In 1838 the Tawells returned finally to London. Mary, who had been suffering from tuberculosis, died by the end of the year. Tawell had employed a nurse, Sarah Hadler, who later changed her name to Sarah Hart, to look after Mary and began an affair with her, despite himself having remarried. This secret relationship with Sarah Hart bore two children, and Tawell installed all three in a cottage in Salt Hill, Slough where he paid £1 per week to maintain them.