Hon. John Sugiyama (Ret.) is a Mediator at JAMS with extensive experience in adjudicating complex legal matters and resolving disputes through alternative dispute resolution processes. He served for 18 years on the Contra Costa County Superior Court, spending the last nine years as the supervising judge for the Probate Division. Prior to his judicial appointment, Judge Sugiyama held prominent legal positions, including senior assistant attorney general in both the criminal and civil divisions of the California Department of Justice and deputy director and chief counsel for the California Department of Corrections. His deep expertise spans probate law, estate and trust litigation, conservatorships, guardianships, and sensitive family-related legal disputes. Additionally, he played a pivotal role in shaping probate law and court administration as chair of the Judicial Council of California’s Probate and Mental Health Advisory Committee from 2014 to 2019.
Throughout his distinguished career, Judge Sugiyama was recognized for his intellectual rigor, compassionate judicial temperament, and ability to facilitate equitable resolutions. He authored numerous well-reasoned judicial opinions on complex probate, trust, and conservatorship matters, including high-stakes disputes involving testamentary capacity, undue influence, and fiduciary obligations. His background in both trial and appellate advocacy—having personally briefed and argued hundreds of cases with over 40 published opinions—further underscores his exceptional legal acumen. In addition to his judicial service, Judge Sugiyama has been a sought-after speaker and educator in the legal community, offering insights on probate litigation, mediation, and effective advocacy. Now at JAMS, he continues to apply his vast experience to help parties navigate and resolve challenging legal disputes through mediation and private judging.
