In law, we often refer to one’s legal “capacity.” In this context, it refers to one’s mental capabilities. There are several levels of legal capacity, including but not limited to contractual capacity, testamentary capacity, and the capacity to marry. These different standards of capacity relate to our ability to legally engage in certain acts: the ability to enter into a contract, to execute a will, and to lawfully marry, respectively. These standards often become relevant as we age, and begin losing our mental faculties.

Each kind of capacity has its own standards of mental capabilities and abilities; the mental capacity needed to enter into a contract is the highest, meaning you have to have very little loss of mental capabilities in order to execute a binding contract.

Under California Probate Code Section 4609, "capacity," generally, means a person's ability to understand the nature and consequences of a decision and to make and communicate a decision, and in the case of proposed health care, the ability to understand its significant benefits, risks, and alternatives.

Contractual capacity is specifically defined by common (case) law in the Estate of Bodger (130 Cal.App.2d 416 (1955)), which looked at whether the contracting individual understood the nature and extent of the transaction. From an estate planning point of view, this standard is relevant because it dictates the capacity necessary to execute a power of attorney, and a trust – although some California courts have begun to apply the lower standard of testamentary capacity (discussed below) where a trust or other contractual agreement is in essence a testamentary document.

Testamentary capacity (the capacity to make a will) is determined pursuant to California Probate Code Section 6100.5, which provides in relevant part:

(a) An individual is not mentally competent to make a will if at the time of making the will either of the following is true:

  1. The individual does not have sufficient mental capacity to be able to (A) understand the nature of the testamentary act, (B)understand and recollect the nature and situation of the individual's property, or (C) remember and understand the individual's relations to living descendants, spouse, and parents, and those whose interests are affected by the will.
  2. The individual suffers from a mental disorder with symptoms including delusions or hallucinations, which delusions or hallucinations result in the individual's devising property in a way which, except for the existence of the delusions or hallucinations, the individual would not have done.

With respect to health care decisions, California Probate Code Section 813 provides factors for a judicial determination of capacity:

Can the patient:

  1. Respond knowingly and intelligently to queries about the medical treatment?
  2. Participate in the treatment by means of a rational thought process?
  3. Understand:
    1. The nature and seriousness of the illness?
    2. The nature of the medical treatment?
    3. The probable degree and duration of the risks and benefits of the treatment, and the consequences of lack of treatment?
    4. The nature, risks, and benefits of reasonable alternatives?