Judge Corkill was admitted as a barrister and solicitor in New Zealand in 1975 where he practised briefly. He then worked in England until 1982, becoming a Solicitor of England and Wales. After returning to New Zealand and practising in general litigation in two firms, he commenced practice as a barrister in 1997, taking silk in 2007. Over those years, he had a broad civil practice, which included not only employment law, but litigation where he represented Māori corporate and individual interests.
He was then appointed a Judge of the Employment Court in 2014