A court lawyer for over 30 years, John has been a QC since 2011.

He has been instructed in some of the most significant, complex and high-profile cases of recent times. In some of these, including human rights cases at the UK Supreme Court, he has presented arguments which have helped to develop the law.

John chaired the Scottish Human Rights Centre from 1997 to 2005.

In 2014, he chaired human rights organisation Justice Scotland for a year.

He was Convenor of the Howard League for Penal Reform in Scotland from 2006 until 2018.

John has completed work in chairing several independent reviews for the Scottish Government.

He has chaired the Scottish Mental Health Law Review since May 2019.