Final answer:
The statement is true; patients have the right to stop an exam, but if they lack decision-making capacity, a designated POA can make decisions for them. The presumption of patient competence is a legal standard upheld by case law unless legally determined otherwise.
Step-by-step explanation:
The statement that a patient always has the right to stop an exam unless they are incapable of decision-making and have a Power of Attorney (POA) is true. In medical ethics, patient autonomy is a fundamental principle, which implies that patients have the right to make decisions about their own healthcare. Even if a patient initially consents to an examination or procedure, they can withdraw consent at any time. However, if a patient lacks decision-making capacity and is legally unable to provide consent, then the decision falls to the individual with the legal authority to make decisions on their behalf, often through a POA or guardianship arrangement. In legal terms, competence is the ability of an individual to make informed decisions. The presumption of competence is established by cases such as Dusky v. United States and Rogers v. Okin, which affirm that individuals are presumed competent unless adjudicated otherwise by a court or a similar legal process.