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Introduction
This thesis is a philosophical critique of the best interest test, the legal mechanism for
health care decision making on behalf of adults who lack capacity in England and New
Zealand. My thesis is that the current use of the best interest test ignores an integral part
of decision making – the role of values.
The existing process claims to use science-based, value free philosophies, which are
supposed to underpin clinical practice and legal reasoning in best interest
determinations. But there is an inevitable interrelationship between facts and values in
the process of decision making on behalf of adults who lack capacity and in processes
and systems of law and medicine. This is not acknowledged.
The fundamental choices which lie behind best interests’ determinations are masked
from scrutiny. This is to the detriment of the adults on whose behalf decisions are
made, the decision makers themselves (the judiciary and health professionals) and
society. I argue that the integral place of values in decision making can, and must be,
revealed to improve transparency, honesty and credibility, and inform decision making.
The best interests test as a decision making mechanism
For competent adult patients the law is clear; an individual’s autonomy and right to
self-determination in accepting or declining medical treatment are absolute. “A person
is completely at liberty to decline to undergo treatment, even if the result of his doing
so will be that he will die” (Lord Keith, Airedale NHS Trust v Bland [1993] (England)
at 859). However, for the incompetent adult, the law in England and New Zealand is
reliant on the best interests test.
The test has been widely used as a legal principle to justify health care treatment and
non-treatment decisions on behalf of incapacitated adults since it was first applied,
along with the common law principle of necessity, to justify medical treatment for an
adult who lacked capacity to consent to treatment in Re F [1990] (England). This case
concerned a woman with an intellectual disability who lacked capacity to consent to
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