He was admitted to practice in Western Australia in 1977, and was a partner of the law firm Keall Brinsden (now Corrs Chambers Westgarth) until joining the independent bar in 1988.

[5][6] He also came to the defence of the legal system in the wake of criticisms in some sections of the media that resulted from several high-profile miscarriages of justice.

[9] In his role as Lieutenant-Governor, he has served as Administrator of the State on two occasions when the position of Governor of Western Australia is vacant: from 2 May to 1 July 2011, following the expiration of Ken Michael's term, and from 1 July 2014 to October 2014, following the expiration of Malcolm McCusker's term.

[12] Martin became a West Australian Football Commission board member in 2019 before being elected chairman in 2020 and then reappointed on a three-year term in December 2021.

[14] On 11 June 2012, Chief Justice Martin was named an Companion of the Order of Australia for "eminent service to the judiciary and to the law, particularly as Chief Justice of the Supreme Court of Western Australia, to legal reform and education, and to the community".