Gallows Thief by Bernard Cornwell

Gallows Thief: A Novel - Rider Sandman is an impoverished gentleman who is known for his bat in cricket. The Home Secretary, Lord Sidmouth, hires him to investigate the innocence of a painter, Charles Corday, who is to be hanged for murder. It is made quite clear that Sandman is to beat a confession out of Corday to satisfy all prosecuting parties that they have done the right thing. But Rider has doubts about Corday’s guilt and begins a true investigation.