On 20 April 1770, Smart was arrested for debt. On 11 January 1771, he was tried by Lord Mansfield, the gentleman who originally introduced Smart to Alexander Pope, and he was soon recommended to the King's Bench Prison. Although he was in prison, Charles Burney purchased the "Rules" (allowing him some freedom), and Smart's final weeks may have been peaceful although pathetic. In his final letter, Smart begged for money from Rev. Mr. Jackson, saying: "Being upon recovery from a fit of illness, and having nothing to eat, I beg you to send me two or three shillings which (God willing) I will return, with many thanks, in two or three days." On 20 May 1771, Smart died from either liver failure or pneumonia shortly after completing his final work, "Hymns, for the Amusement of Children".