Born in the northern Perth suburb of Karrinyup, Tinley joined the Australian Army in 1981 and graduated from Royal Military College, Duntroon, earning the Queen's Medal as the cadet graduating top of his class. He spent 17 of his 25 years in the army in the Special Air Service Regiment (SASR). In 2002, he was the lead tactical planner for Australia's special forces advising the United States, and in 2003 he served as Deputy Commander for the Special Forces Task Group in Iraq. In the same year, he was appointed a Member of the Order of Australia (AM) in the military division for "dynamic leadership and consistent professional excellence".