Consent is valid when a patient with capacity makes a voluntary decision on the information they need, and capacity is presumed for every adult until it is shown to be absent. The Mental Capacity Act 2005 sets the legal test, GMC Decision Making and Consent 2020 sets the professional standard, and the same GMC guidance answers the question the CST management station likes most: what you do when a registrar asks you to consent a patient for an operation you do not understand well enough to explain.
Key takeaways
- Section 1 of the Mental Capacity Act 2005 states that a person must be assumed to have capacity unless it is established that they lack it, and that an unwise decision is not proof of incapacity.
- Section 2 requires an impairment of, or disturbance in the functioning of, the mind or brain; section 3 requires inability to understand, retain, use or weigh the information, or to communicate the decision.
- Section 2(4) sets the standard of proof: any question of capacity is decided on the balance of probabilities.
- GMC Decision Making and Consent 2020, paragraph 44, says anyone you delegate the consent conversation to must be suitably trained and competent, with sufficient knowledge of the intervention, its benefits and harms, and the alternatives.
- GMC paragraph 47 tells a doctor asked to seek consent on a colleague's behalf to be satisfied they have the necessary knowledge and skills, and otherwise to explain this and seek support.
- In an emergency where a patient lacks capacity, GMC paragraph 63 permits treatment that is immediately necessary to save life or prevent serious deterioration, choosing the least restrictive option.
What is the principle behind consent and capacity?
The principle is autonomy: an adult with capacity decides what happens to their own body, and the doctor's job is to make that decision an informed one.
GMC Decision Making and Consent 2020 puts it as seven principles. Principle one states that all patients have the right to be involved in decisions about their treatment and care.
Principle five states that doctors must start from the presumption that all adult patients have capacity, and that a patient can only be judged to lack capacity for a specific decision at a specific time.
That decision-specific, time-specific framing is what the CST panel wants to hear. A patient with dementia may lack capacity for an operation and still have it for a blood test.
What is the legal test for capacity under the Mental Capacity Act 2005?
The Mental Capacity Act 2005 test has two stages: an impairment or disturbance of the mind or brain, and an inability to make the decision because of it.
Stage one: the diagnostic element
Section 2(1) of the Act states that a person lacks capacity if, at the material time, they are unable to make a decision for themselves because of an impairment of, or a disturbance in the functioning of, the mind or brain.
Section 2(2) adds that it does not matter whether the impairment is permanent or temporary, which is why post-operative delirium, sepsis and opioid sedation all count on a surgical ward.
Stage two: the functional element
Section 3(1) of the Act states that a person is unable to make a decision if they cannot understand the information relevant to it, retain it, use or weigh it as part of the process, or communicate the decision by any means.
Section 3(3) states that retaining the information only for a short period does not prevent the person being regarded as able to decide. A brief memory is still enough.
The safeguards around the test
Section 1(3) states that a person is not to be treated as unable to decide unless all practicable steps to help them have been taken without success. Hearing aids, interpreters, a quieter time of day and a family member all count.
Section 1(4) states that an unwise decision is not proof of incapacity, and section 2(3) states that incapacity cannot be established merely by reference to age, appearance, condition or behaviour.
Section 68 states that the Act extends to England and Wales only. GMC paragraph 87 notes that the equivalent legal concept is 'benefit' in Scotland and 'best interests' in England, Wales and Northern Ireland.
What does GMC Decision Making and Consent 2020 require of the conversation?
GMC Decision Making and Consent 2020 requires a dialogue tailored to what matters to the patient, not a signature on a form.
Paragraph 10 states that you must give patients the information they want or need, which usually includes the diagnosis and prognosis, the uncertainties, the options including taking no action, and the nature and desired outcome of each option.
Paragraphs 16 to 19 state that you must listen, encourage questions, and try to find out the patient's wishes, fears and priorities so you can identify which information would influence their choice.
Paragraph 23 states that the discussion of harms should usually include the recognised risks anyone in the patient's position would want to know, the risks the patient would consider significant for any reason, and any risk of serious harm however unlikely.
Paragraph 31 states that you must not exceed the scope of a patient's consent except in an emergency, so a change of operation on the table needs prior agreement or a real emergency.
What happens when a patient lacks capacity?
When a patient lacks capacity, a decision is made in their best interests under section 4 of the Mental Capacity Act 2005, and the treating doctor is protected by section 5 if they took reasonable steps and held a reasonable belief.
Section 4 requires the decision maker to consider whether the person is likely to regain capacity and when, to permit and encourage their participation, and to consider their past and present wishes, beliefs and values, including any written statement made with capacity.
Section 4(7) requires consultation, where practicable and appropriate, with anyone the person named, anyone caring for them, any attorney under a lasting power of attorney and any court-appointed deputy.
GMC paragraph 86 states that if the patient may regain capacity and the decision can be delayed, you must consider delaying it. GMC paragraph 88 tells the treating doctor first to check for a binding advance decision and for anyone with legal authority to decide.
GMC paragraph 63 covers the emergency: if a patient is unconscious or lacks capacity and their wishes cannot be found, you can provide treatment immediately necessary to save life or prevent serious deterioration, choosing the least restrictive option.
What should you do if asked to consent a patient beyond your competence?
If asked to take consent for a procedure you cannot explain properly, GMC Decision Making and Consent 2020 says you must be satisfied you have the knowledge and skills; if not, explain this and seek support.
Paragraph 47 states exactly that, and adds that if you believe you are being asked to practise outside your competence, or are insufficiently supported, you must consider raising a concern.
Paragraph 44 places the matching duty on the surgeon who delegates: the person they delegate to must be suitably trained and competent, know the intervention, its benefits, harms and alternatives, and be able to hold the dialogue.
Paragraph 45 states that the delegating doctor remains responsible for making sure the patient had the information, the time, and gave consent before treatment.
RCS Good Surgical Practice, section 2.4, says the same in surgical terms: consent is obtained by the person providing the treatment or by someone suitably trained and qualified to provide it, with sufficient knowledge of the risks and complications.
The answer the panel wants is therefore not a refusal and not a compliant signature. It is: I would say I cannot consent this patient safely, offer what I can do, and ask the operating surgeon to have the conversation or to supervise me.
How would a worked scenario run in the station?
A typical CST scenario: a 78-year-old man with an obstructed hernia needs surgery tonight, seems confused, and the registrar, scrubbed on another case, asks you to consent him.
Step one: is this an emergency that cannot wait?
Ask how much time there is. If the patient is peritonitic and deteriorating, GMC paragraph 63 applies and the least restrictive life-saving treatment can proceed while the consultant is called.
Step two: assess capacity properly
Apply section 2 and section 3 of the Mental Capacity Act 2005 at the bedside: is there an impairment, and can he understand, retain, weigh and communicate? Take the practicable steps first: glasses, hearing aid, a relative, a quiet room, treat pain.
Step three: be honest about your own competence
If you have not seen a hernia repair for a strangulated hernia and cannot describe the risk of bowel resection or stoma, say so. Paragraph 47 requires it. Offer to gather the history, examine and document capacity, and ask the registrar or consultant to consent.
Step four: document and involve the right people
Record the capacity assessment, the practicable steps taken, who was consulted under section 4(7), and who took consent. Tell the anaesthetist and the theatre coordinator early.
What is the interviewer listening for?
The CST panel listens for the two-stage Mental Capacity Act test said in order, the presumption of capacity said first, and honesty about your own limits.
- The presumption of capacity and the two-stage test named as sections 1, 2 and 3 of the Mental Capacity Act 2005
- Practicable steps to support the decision before concluding capacity is absent
- Best interests under section 4 as a process with named consultees, not a doctor's opinion
- GMC paragraphs 44, 45 and 47 on delegation, said as duties on both the delegator and the delegate
- A plan that keeps the patient safe while the right person takes consent
What is the trap in this question?
The trap is treating a difficult or refusing patient as an incapacitous one, and treating the registrar's request as an instruction you must obey.
Section 1(4) of the Mental Capacity Act 2005 is explicit that an unwise decision does not prove incapacity. A capacitous refusal of life-saving surgery must be respected, documented and escalated, not overridden.
The other half of the trap is the opposite failure: refusing to help at all. GMC paragraph 47 asks you to explain and seek support, not to walk away from the patient.
What is the escalation route?
Escalate to the operating surgeon for the consent conversation, to the consultant for any disputed capacity or best-interests decision, and to the trust's legal or safeguarding team when the dispute cannot be resolved.
GMC paragraph 85 states that in complex cases you should seek specialist input, for example from psychiatry or a liaison nurse, and that you should do so if the patient or those close to them disagree with your judgement.
An independent mental capacity advocate is worth naming for an unbefriended patient facing serious treatment, and the Court of Protection is the final route for a serious dispute.
How does consent link to the portfolio domain?
Consent links to the CST portfolio through the Quality Improvement and Clinical Audit domain, because a consent-documentation audit against GMC standards is one of the commonest closed-loop projects a foundation doctor can lead.
NHS England's 2025/26 CST portfolio guidance grades level A in that domain as leading all aspects of a surgically themed audit or QI project that demonstrated change, such as a second cycle. A consent audit with a re-audit after a template change fits that exactly.
It also shows the panel that you understand the standard you are auditing, which is why the two stations reinforce each other.
How this comes up at the CST interview
Consent and capacity appears in the CST management and clinical station as a scenario, usually a confused or refusing patient, with a follow-up about being asked to consent beyond your competence.
Practise saying the two-stage test, the section 4 process and GMC paragraph 47 aloud until they come out in under a minute. coresurgeryinterview has a scored management scenario on consent in its 299-question bank, with AI-marked spoken practice: /Question-Bank/Sample-Questions.