Mann was elected to the
South Australian House of Assembly as member for
Burra on 14 April 1870. Mann was four times
Attorney-General of South Australia — from 21 July 1871 to 22 January 1872 (in the last
John Hart government until 10 November 1871, afterwards in the
Arthur Blyth Ministry which immediately followed it); in the third Blyth Ministry, from 22 July 1873 to 3 June 1875; in the second and third
James Boucaut governments, from 25 March to 6 June 1876 and 26 October 1877 to 27 September 1878. Mann was Treasurer in the
William Morgan administration, from 27 September 1878 to 10 March 1881, when he was appointed Crown Solicitor and Public Prosecutor, both of which positions he filled till his death on 7 July 1889. ==Personal==