When a person drafts a will in California, he or she must exhibit his or her testamentary capacity. According to The Journal of the American Academy of Psychiatry and the Law, this is the competency to create a will. It demonstrates that at the time the will was written the person was mentally sound. This is important later on when the person dies and the will is executed. Not showing testamentary capacity could mean a contested will and a long legal battle.

According to the American Bar Association, there are two definitions of testamentary capacity in the state of California: one for the creation of a will and one for entering into business contracts. It is essential that when a court decides on this issue that the correct definition is used because they differ greatly in intensity with the criteria for creating a will be less restrictive than the capacity for entering a business contract.

When it comes to the creation of wills, the competency required is based on only three factors. The person creating the will must understand who his or her heirs are and the relationships with those heirs. The person must also understand his or her estate and what assets he or she has to give to the heirs. Finally, the person needs to understand that he or she is creating a will and what that means. If it is determined that a person understands these three points, then he or she can create a legally valid will.