Doctor’s Diagnosis and Opinion to determine incapacity

A doctor’s opinion is not necessary to establish lack of capacity. Indeed, a diagnosis of a mental or physical disorder is not, by itself, sufficient evidence for a finding that one lacks the legal capacity to contract, convey, marry, make medical decisions, and so forth. Prob C §810. Nevertheless, a doctor’s opinion is persuasive evidence, especially if the petitioner can correlate it with the proposed conservatee’s behavior. For example, if the proposed conservatee is diagnosed with anxiety and depression (see Prob C §811(a)(4)), the petitioner should illustrate the effect of the disorder on the proposed conservatee’s ability to make decisions.

Does the Proposed Conservatee Lack Capacity

The Due Process in Competence Determinations Act (DPCDA) (Prob C §§810–813, 1801, 1881, 3201, 3204, 3208) sets forth guidelines for assessing the proposed conservatee’s legal competence. Probate Code §810 begins by codifying the presumption that all persons have the capacity to make their own decisions and take responsibility for their own actions. This presumption affects the burden of proof. Prob C §810(a). To overcome the presumption and obtain an order establishing a conservatorship, the petitioner must prove by clear and convincing evidence that the proposed conservatee either cannot provide for his or her own personal needs (conservator of the person; Prob C §1801(a)) or cannot manage his or her financial resources or resist fraud or undue influence (conservator of the estate; Prob C §1801(b)). Prob C §1801(e).

Setting Aside a Will or Trust for Lack of Capacity

Will contests and attacks on trusts often involve the question of whether the testator or settlor had the requisite mental capacity at the time the instrument was executed. In most cases, the analysis of capacity to execute wills and trusts is the same. More stringent tests for capacity may apply to trusts, however, when they are irrevocable or when property is transferred to an independent trustee.


To make a valid will, the testator must be at least 18 years of age and of sound mind. More specifically, a person is not mentally competent to make a will if at the time of making the will he or she either:

  • Does not have sufficient mental capacity to (1) understand the nature of the testamentary act, (2) understand and recollect the nature and situation of his or her property, or (3) remember and understand his or her relations to living descendants, spouse, parents, and others whose interests are affected by the will; or
  • Suffers from a mental disorder with symptoms including delusions or hallucinations that result in his or her devising property in a way that, except for the delusions or hallucinations, he or she would not have done.

A testator’s beliefs may be inaccurate without being delusional. A mere unfounded belief does not justify overturning a will when there is any evidence supporting the belief. To destroy testamentary capacity, a delusion must be one so irrational that no normal person could have it.

To justify setting aside a will, the alleged delusions or hallucinations must cause the testator to devise his or her property in a way that he or she would not have done in their absence. It is not sufficient merely to establish that a testator was the victim of delusions or hallucinations.