Douglas Benson (defendant) and Diane Benson (plaintiff) were married. Diane filed a petition for dissolution of the marriage. Douglas worked full-time and had a 401(k) retirement account through his employer. Diane’s father initially owned the house in which the couple lived. Diane’s father deeded the couple a 100 percent ownership interest in the house. Diane’s father later requested that the house be deeded to Diane’s irrevocable trust, of which her father was the trustee. According to Douglas, he agreed to transfer ownership of the house to the trust, but only upon a verbal commitment from Diane that she would give up any interest in Douglas’s retirement accounts. The agreement was never reduced to writing, and at trial Diane denied making the agreement. Douglas separately settled his claim regarding his interest in the house. Diane argued that the claimed transmutation of Douglas’s retirement accounts was invalid due to section 852(a) of the California Family Code. Section 852(a) provided that a transmutation of community property must be made expressly in writing. The trial court found that Douglas deeding the house to the trust was part performance of the oral transmutation agreement, rendering the agreement enforceable against Diane. The court of appeal affirmed. Diane appealed.