Judge Erns Jansen was born in Pietermaritzburg on 27 June 1918. He was the son of Ernest Jansen, Minister of Native Affairs in the National Party government and Governor-General of the Union of South Africa. While he was born into the Afrikaner aristocracy, he never became a Broederbond member and remained apolitical.
He matriculated from Afrikaans Boys' High School in Pretoria, attained his BA LLB cum laude at Pretoria University and began practising as an advocate in 1943. Jansen became a Queen's Counsel in 1955, a judge in Natal in 1957 and also in the Transvaal in 1961. He was appointed to the Appellate Division in 1968.
During his time many judges of the Appellate Division were appointed for political reasons rather than for their legal expertise, but Judge Jansen was one of the few who were appointed on merit. He was an Appeal Court judge for 20 years.
A judgment he wrote in 1983 in Mandela v Minister of Prisons underlined the point. He upheld the right of prisoners to give written instructions to their legal advisers without needing the approval of the commissioner of prisons.
In State v Marwane 1982, a Mr Marwane sought leave to appeal after being convicted in the "independent" homeland of Bophuthatswana under South Africa's Terrorism Act. South African human rights lawyers argued that this act offended against the Bophuthatswana constitution. In a highly significant judgment Judge Jansen agreed with them.
He excelled in commercial cases where he was known for his thorough research. This research was vindicated by the number of minority judgments he wrote which were subsequently, sometimes 14 or 15 years later, upheld or at least influential in shaping modern law, particularly in the area of contracts and their interpretation.
An important instance where his views did not prevail was his espousal, in 1988, of the notion of good faith as a general principle of the law of contract. The recent adoption by the legislature of the Consumer Protection Act is seen as a vindication of this view.
Judge Jansen was one of South Africa's last great scholars of Roman Dutch law and one of the most academic and analytical of the country's judges. In some instances, he was often so scholarly, academic and analytical in his approach, that he saw things from a variety of angles which made it painfully difficult to come to a conclusion.
Judge Jansen was quiet, urbane, gentle and kind. He treated everyone, from witnesses to junior and senior counsel, with respect, patience and understanding.
He was prodigiously good at languages. He spoke several, including French and Zulu, fluently. He read Latin as easily as his colleagues read English or Afrikaans.
Although he was next in line to succeed Chief Justice Pierre Rabie, he was not considered for the job.
Judge Jansen retired from the bench in 1988 and the following year his wife Rona died. Erns Jansen, died in Pretoria at the age of 92. He is survived by his three daughters.