Mr. Mirieri is an Advocate of the High Court of Kenya. He is an alumnus of the University of Nairobi where he received LL. B and Masters of Law degrees and holds a Masters of Arts in Management from Hamline University and Postgraduate Diploma in law from the Kenya School of Law.

He engages in general practice of the law with a concentration in Land and Environment, Commercial Law, Industrial Relations Unions and Employment Law, Property Conveyancing Land Landlord and Tenant Law, Constitutional and Human Rights Law and Criminal Law.