Muller holds an LLB and an LLD in international law. He has worked as a state advocate, an additional magistrate and joined the Bar in 1991, being conferred silk in 2009.
Muller has appeared at the Constitutional Court in matters including S v Nabaliso – the latter being the co-convicted in a drugs smuggling case involving Sheryl Cwele, the former wife of former intelligence minister Siyabonga Cwele.
He has published four papers, including “Unfair labour Practise and Dismissal” and “The Liability of Banks as Moneylenders for Damages to the Environment”. He has acted in the North Gauteng High Court in various stints between 2010 and 2014.
Muller was quizzed on his professional history – both while acting as a high court judge, and while working as a silk. He has argued five reported cases at the Supreme Court of Appeal and a further five at the Constitutional Court, including one involving Frank Nabolisa, the drug dealer convicted of trafficking cocaine with Sheryl Cwele, the former wife of intelligence minister, Siyabonga Cwele.
On his commitment to transformation, Muller said that he used black juniors regularly, including in matters which he had argued at the Constitutional Court. He said his appointment to the Limpopo high court — as a white male — would ensure representivity on that Bench.