Griggs' specialty is trauma and retrieval; until his retirement from medicine he was the Director of Trauma Services (from 1995) and Senior Consultant (Intensive Care, Retrieval Services and Anaesthetics) (from 1989) at Royal Adelaide Hospital. He was Director, Retrieval Coordination for MedSTAR Emergency Medical Retrieval. From 2007 until 2018 he was the South Australian State Controller (Health and Medical) for disasters. He is a Clinical Associate Professor at Adelaide University and has previously been a senior lecturer at Griffith University and the University of Otago. He also worked for the South Australian Ambulance Service from the early 1980s until 2019, and has been a volunteer with St John Ambulance Australia since the mid-1970s. He was one of the founding members, is a past President, and is an Honorary Life Member of the Australasian Trauma Society.