The 2015 UK Supreme Court judgment in Montgomery v Lanarkshire reinforces the importance of informed consent to medical treatment. This paper suggests that Montgomery recognises the challenge faced by vulnerable individuals in choosing between treatment options and making decisions with appreciation of information about material risks. The judgment endorses a form of weak paternalism to safeguard such persons, which is not disrespectful of the aggregate principles of the Mental Capacity Act 2005. But ethical practice requires professionals to tread carefully between weak and hard paternalism in the context of therapeutic interactions with vulnerable patients, while ensuring their awareness of material risks.

Background The assessment of patients’ decision-making capacity is ubiquitous in contemporary healthcare. This paper examines the ethics of undisclosed probing of capacity by psychiatrists. The discussion will refer to the law in England and Wales, though the highlighted issues are likely to be relevant in similar jurisdictions. Main text Decision-making capacity is a private attribute, and patients may not necessarily be aware that one of their personal abilities is being explored. Routine exploration of capacity has not historically been a part of psychiatric examination, but it is now difficult to avoid during psychiatric interview.Ethical practice and shared decision-making require patients to be aware that their decision-making may be evaluated by the doctor at some point, and the potential implications of an objective professional conclusion of incapacity. Case law directs that patients should be informed about any assessment of their decision-making ability, though the extent to which this has translated into practice is unclear. However, explanation about the assessment may cause a patient to react negatively, which may impede therapeutic engagement and constitute an ethical dilemma. It is argued that in the absence of systemic measures, professionals should retain the discretion to decide whether a particular patient should be informed about the impending probe into their decision-making ability, or not. In the latter instance, concealment of information about the assessment or its purpose should be subject to the caveats and safeguards associated with any recourse to therapeutic exception. Conclusion The necessity to mandatorily inform patients about assessment of their capacity introduces a novel ethical dilemma for psychiatrists. The negotiation of this dilemma should not be the prerogative of the clinician, and requires systemic initiatives to ensure universal awareness of patients about the possibility of their capacity being assessed during their journeys through healthcare systems.