 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.