The 56-year-old holds a PhD in Law from University of Ghent, Belgium, a Master of Laws degree from the Columbia University in the United States of America and a Bachelor of Laws (LLB) Degree from the University of Nairobi.
Dr. Wanjala lectured at the University of Nairobi for 15 years where he taught International Law, International Human Rights Law, Land Law and Criminal Law.
The Supreme Court Judge served as a deputy director in charge of prevention of the now defunct Kenya Anti-Corruption Commission. He was appointed to the position on 9 September 2004 for a period of five years and was responsible for Research, Policy and Preventive Service.
He resigned on 18 September 2009 due to public outcry following the irregular reappointment alongside his boss Aaron Ringera and fellow deputy director Fatuma Sichale by President Mwai Kibaki.
The Judicial Service Commission interviewed a total of 25 applicants for the positions of Supreme Court Judges.Smokin found his name among the successful candidates after impressing the panel.
In 2012, he was nominated to the Supreme Court of Kenya by the Judicial Service Commission
Dr Wanjala was among the six Supreme Court judges who delivered the famous landmark ruling involving President Uhuru Kenyatta and former Prime Minister Raila Odinga.In the ruling, the six judges upheld Uhuru’s election as the president and dismissed Raila’s election petition.
On September 3, 2016, Smokin appeared before the Judicial Service Commission for the interview of Chief Justice of Kenya. The sharp judge answered 99.9 % of the questions brilliantly, prompting the panel to agree with almost every answer he gave.Going by the mood in the house,Smokin might succeed Mutunga.