A more thorough explanation:

The substituted-judgment doctrine is a principle that allows a surrogate decision-maker to make decisions on behalf of an incompetent patient. The decision-maker attempts to establish, with as much accuracy as possible, what decision the patient would make if he or she were competent to do so. The standard of proof is by clear and convincing evidence. Generally, the doctrine is used for a person who was once competent but no longer is.

For example, if a person becomes incapacitated and unable to make medical decisions for themselves, a family member or legal guardian may be appointed to make decisions on their behalf. The decision-maker would use the substituted-judgment doctrine to make decisions that align with the patient's wishes and values.

The substituted-judgment doctrine is an important ethical principle in healthcare, as it allows for patient autonomy and respects the patient's right to make decisions about their own care.