Born and educated in Perth, Justice Deane graduated in law from the University of WA in 1976 and went on to complete a postgraduate degree in Social Work, also at the University of WA. Justice Deane was admitted to practise as a barrister and solicitor in February, 1980 and worked within the Crown Law Department, carrying out a wide variety of work over many jurisdictions. She frequently appeared as counsel, particularly in criminal matters, and in 1992 became a founding member of the Office of the Director of Public Prosecutions. Since then she has gained extensive criminal law experience, having the carriage of many high profile prosecutions. Justice Deane has also appeared in a number of important appeals, including appearances in the High Court of Australia. Justice Deane was appointed a Queen's Counsel in 1996. She has been both chairperson and a member of the Board of Management of Centrecare Marriage and Family Service (Western Australia). Justice Deane was appointed to the District Court of Western Australia in February 1998. She was the first woman Queen's Counsel to be appointed to the District Court. Justice Deane retired from the District Court in 2014.