Before joining the bench, Judge Diane Ritchie was a partner of Employment Rights Attorneys. She also managed her own employment law office in San Jose for eight years, and subsequently worked as the Supervising Attorney of the Employment Law Unit of the Legal Aid Society of Santa Clara County. She also worked for the insurance defense firm of Williams Kelly. While working as an attorney, she taught employment law and employee relations to MBA and undergraduate students at the College of Business and Economics at California State University, East Bay.
During her time as a judge of the Superior Court of California, County of Santa Clara, Judge Diane Ritchie presided over thousands of criminal and civil cases including criminal cases like child abuse, domestic battery, and rape, and civil cases like personal injury, fraud, breach of contract, and high-tech business disputes. As a civil trial judge, she settled over a third of the civil trial cases presented to her.