John Lowndes was born in Sydney and did his combined undergraduate degree at the University of Sydney (BA.LLB 1976). His post graduate qualifications include a Diploma of Criminology (1984), Diploma of Jurisprudence (1987) and a Master of Laws (Class 1 Honours) (1991) also from the University of Sydney. He also holds a Degree of Doctor of Philosophy from Charles Darwin University (2005).

He began his career as a solicitor in a Sydney firm specialising in criminal and family law, and continued to practise until his appointment in 1990 as a stipendiary magistrate of the Northern Territory. In early 2013 he was appointed Deputy Chief Magistrate of the Northern Territory and later that year as Chief Magistrate.  In 2016 he was appointed as Chief Judge of the Local Court (formerly the Magistrates Court), a position which he held until his retirement in October 2019.

For almost 30 years on the bench he  exercised the broad criminal and civil jurisdiction of the Magistrates Court/Local Court, which is equivalent to the jurisdiction of a District Court or County Court elsewhere in Australia. During that time he was also the Coroner for the Northern Territory, Managing Magistrate of the Work Health Court, President of the Mental Health Review Tribunal (under delegation from the Chief Magistrate) and Chairperson of the Lands Planning and Mining Tribunal.

He is a former President of the Australian Association of Magistrates (AAM) and the Commonwealth Magistrates and Judges Association (CMJA).

He has been a Fellow of the Australian Academy of Law (FAAL) since 2017.  In 2019 he was “Judge in Residence” at the ANU College of Law. In 2020 he was awarded the Order of Australia Medal (OAM) for “Service to the Law and the Judiciary”.