Douglas has been in practice as a barrister since admission to the New Zealand Bar in 1996. He was also admitted in Samoa in 2000. His work varies from human rights litigation and judicial review to criminal appeals and trials.


Douglas has an acknowledged reputation for judicial review cases, especially as they relate to decisions arising from criminal cases in the District Court. He also practices in the field of human rights, including civil cases against the State for false imprisonment, unlawful searches and breaches of the New Zealand Bill of Rights. 


Additionally, Douglas practices in all areas of criminal law and has been briefed to appear for the defence in cases all over New Zealand, although his practice is based primarily in Wellington.


He lectured at Victoria University, Wellington, in advanced criminal procedure. He also publishes practice guides for Thomson Reuters, setting out practical ways to conduct both civil and criminal cases and is the co-author of Appeals and Judicial Review in Criminal Proceedings.