US law presumes capacity to once someone reaches the age of consent for an act defined in their state laws. For example, in Massachusetts, the age of sexual consent is 16 years and the age of majority, when one can give legal consent, is 18 years.
An adult (someone over the age of majority) is entitled to all of their rights and privileges unless limitations are imposed by a court or through a professional judgement (Lyden, 2007). The person appointed by the court to make those decisions can be called a lot of things, but I use guardian and guardianship as umbrella terms.
The law requires the presence of three elements to conclude that a person genuinely consents to an activity. These three elements generally apply to almost all consent decisions. For example, they are used in determining whether a marriage, contract, or testamentary will is valid, whether a confession to a crime was voluntary under the constitutional right against self-incrimination, etc.
Those elements are:
- Knowledge: information about the important aspects of a decision and its risks and attendant benefits;
- Intelligence: understanding showing that the knowledge is comprehended and/or is applied in a manner consistent with a person’s values or beliefs; and
- Voluntariness: a person is not subjected to coercion and understands
In a plenary (full) guardianship, guardians will usually make medical and personal decisions for the incapacitated person, such as medical and surgical consents, rehabilitative services, recreational services and possibly residence.
Plenary guardianship is not viewed as the current best practice, with many opting for narrower, better defined roles like a medical proxy or representative payee. In these limited guardianships, guardians have only the responsibilities and authority outlined in the court order.
Guardians have a responsibility to consult with the incapacitated person whenever possible and to the extent the incapacitated person is able to participate in the decision-making. Guardians must act in the incapacitated person’s best interest at all times, while making decisions as closely aligned as possible to what that there is a choice and he or she has the ability to say yes or no the incapacitated person would if he or she were able to.
Supported Decision Making is a newer model that can happen with or without a formal guardianship. This principle engages trusted advisors - typically family or friends, to help with planning and decision making. It is typically used with limited guardianships, like a medical proxy enacted in emergencies.
A decision made using the substituted judgement principle aligns with the decision the person under guardianship would make for themselves based on their values, beliefs, and preferences.
The course of action that maximizes what is best for person and that includes consideration of the least intrusive, most normalizing, and least restrictive course of action possible given the needs of the person.