She has worked as an investigative reporter in Australia and the United Kingdom for over 20 years, writing for The Sunday Times Insight team as well as The Age in Melbourne, The Canberra Times, and The Guardian and The Independent in London. In 1984, Mayman won the Gold Walkley, the highest honour in Australian journalism, and the Bronze Walkley for best newspaper report for her investigation into the deaths of several Aborigines who were in the custody of West Australian police. Human rights groups supported her investigation's claims of human rights abuses, and her reports helped prompt a two-year Royal Commission inquiry into the deaths, leading to reforms within the Australian police and prison systems. Mayman also co-produced and wrote a documentary film about the neo-Nazi movement in Perth, Western Australia, which was a finalist for a 1993 Walkley Award for best television journalism.