Born in Gisborne, Peter attended Victoria University of Wellington, obtaining a Bachelor of Laws with an Honours Degree. He was appointed as a District Court Judge with a specialist Family Court warrant in 1988 and in 2004, he was appointed as the Principal Family Court Judge of New Zealand. In 2012 he was appointed a Law Commissioner, and in 2015 was appointed as the Chief Ombudsman for New Zealand. In 2019, he took up the role of the incumbent President of the Australasia and Pacific region of the International Ombudsman Institute (IOI), and in 2022 took up the role of Second Vice President of the IOI.

Peter has a long association with the Pacific and was seconded to undertake judicial training there, based in Suva. He has travelled regularly to Pacific Island countries, undertaking workshops on family violence and youth justice. He holds the Samoan Matai title of Misa, which was bestowed in 2000. From 2015 to 2016, he was the President of the Association of Family and Conciliation Courts based in the United States, the first New Zealander to hold this position.