In 1856, Denman stood for Parliament unsuccessfully for
Cambridge University. He was elected
Member of Parliament for
Tiverton at the
1859 general election and held the seat until 1865. In 1866, he was re-elected MP for Tiverton. In parliament he interested himself in the reform of the law of evidence in criminal trials, and on 20 June 1860 moved the second reading of the Felony and Misdemeanor Bill, which aimed to assimilate proceedings for a criminal trial to those current in civil trials (at
nisi prius). The bill passed the Commons, but was abandoned after alteration in the Lords. Five years later, 22 February 1865, he successfully carried through a similar measure, the Felony and Misdemeanor Evidence and Practice Bill. The
Evidence Further Amendment Act 1869 (
32 & 33 Vict. c. 68), popularly known as Denman's Act, was his personal initiative. It meant that witnesses professing no religious belief were able to
affirm in courts of justice, and parties previously incompetent were able to give evidence. ==Death and legacy==