[1] Kotzé was born in Cape Town and was given the Christian names of Johannes Gysbert Blanckenberg, but he used the anglicized form, John Gilbert.

It was recorded he was a distinguished student at Utrecht, where he graduated summa cum laude and shared the distinction of being the best classical scholar at the university.

Kotzé undertook further legal training in Britain as a student at the Inner Temple in London, where he met his wife Mary Aurelia Bell.

He, together with the rest of the High Court, was unceremoniously dismissed by Paul Kruger following a dispute over the Testing Rights issue.

The circumstances surrounding this judgement are worth exploring as they are illustrative of the Legal and general state of public administration in the Transvaal at the time during the British Rule and the Volksraad's Constitution, a "document born of political compromise between warring factions rather than any kind of coherent legal document"[citation needed].

As chief justice of the Transvaal Republic he was dismissed by President Kruger when he held that the courts had the right to test against the Constitution, and declare invalid, resolutions and acts passed by the legislature.