CASC Capacity Assessment: How to Score Full Marks Every Time

Capacity assessment stations are among the most commonly tested in the CASC exam — appearing in almost every sitting. Examiners expect you to demonstrate a systematic approach based on the Mental Capacity Act 2005, combined with sensitive communication skills. This is one station type where a structured legal framework gives you a clear advantage if you know it well.

Understanding Capacity in CASC

Capacity assessment in the CASC tests your ability to:

• Apply the legal framework of the Mental Capacity Act 2005 correctly
• Conduct a structured functional assessment with appropriate questions
• Communicate sensitively with patients about complex decisions
• Document findings clearly and justify your conclusions
• Navigate best interests decisions when capacity is lacking
• Distinguish between unwise decisions and incapacity

These stations frequently appear because capacity assessment is a core skill required in everyday psychiatric practice, from consent to treatment through to decisions about accommodation, finances, and personal welfare. In the real world, poor capacity assessments lead to unlawful deprivation of liberty — the stakes are high and examiners know this.

The Legal Framework: Mental Capacity Act 2005

The Mental Capacity Act 2005 (MCA) provides the legal framework for assessing capacity in England and Wales. Scotland has separate legislation (Adults with Incapacity (Scotland) Act 2000), and Northern Ireland has the Mental Capacity Act (Northern Ireland) 2016. For the CASC exam, you will be assessed on the MCA 2005.

The Five Statutory Principles

These five principles underpin everything in the MCA. Examiners may ask you to recite them, and you should be able to explain each one with a clinical example:

1. Presumption of capacity — A person must be assumed to have capacity unless it is established that they lack capacity. In practice: You do not assess capacity simply because someone has a psychiatric diagnosis or because staff disagree with a patient's decision.

2. Support to make decisions — All practicable steps must be taken to help a person make their own decision before concluding they lack capacity. In practice: Have you tried explaining in simpler language? Would written information help? Would a different time of day be better (e.g., when less sedated)? Would an interpreter help?

3. Unwise decisions — A person is not to be treated as lacking capacity merely because they make an unwise decision. In practice: A patient with schizophrenia who chooses to stop medication may have full capacity to make that decision, even though clinicians consider it unwise. The key question is the process of decision-making, not the outcome.

4. Best interests — Any act or decision made on behalf of a person who lacks capacity must be in their best interests. In practice: Best interests is not purely a medical judgement — it must consider the person's wishes, feelings, beliefs, and values.

5. Least restrictive option — Before any act is done, regard must be had to whether it can be achieved in a way that is less restrictive of the person's rights and freedom. In practice: If a patient lacks capacity to manage finances, could a limited arrangement (e.g., managing a weekly allowance with support) achieve the same goal as full financial deputyship?

The Two-Stage Test

The MCA sets out a two-stage test for determining lack of capacity:

Stage 1 — Diagnostic threshold: Does the person have an impairment of, or disturbance in, the functioning of the mind or brain?

This is broad and includes: mental illness, learning disability, dementia, brain injury, delirium, intoxication, or any other condition affecting brain function. You must identify the specific impairment — examiners will expect you to name it (e.g., "Mr Jones has a diagnosis of moderate Alzheimer's disease, which constitutes an impairment of the brain").

Stage 2 — Functional test: If yes, does that impairment or disturbance mean they are unable to make the specific decision at the relevant time?

Important: The diagnostic threshold alone is never sufficient to establish incapacity. A person with severe schizophrenia may have full capacity for many decisions. You must demonstrate the causal link — that the impairment is the reason they cannot make this specific decision.

The Four-Stage Functional Test

The functional test assesses whether the person can:

1. Understand the Information

Can the patient understand the information relevant to the decision? This includes:

• The nature of the decision
• The reasonably foreseeable consequences of deciding one way or another
• The reasonably foreseeable consequences of failing to make the decision

How to assess: Provide the information in accessible language, use aids if helpful (written information, diagrams), and ask the patient to explain the information back to you in their own words. This is not a memory test — you can repeat information and provide it in different ways.

Example questions: - "Can you tell me in your own words what we've been discussing about your treatment?" - "What do you understand about why this medication has been recommended?" - "What might happen if you decide not to have this treatment?" - "What might happen if you do have the treatment?"

What examiners look for: Did you provide the relevant information clearly before testing understanding? Did you use language the patient could access? Did you check understanding by asking them to explain back rather than just asking "Do you understand?"

2. Retain the Information

Can the patient retain the information long enough to make the decision? Note that:

• The person only needs to retain information long enough to make the decision — not indefinitely
• Retention for a short period does not automatically mean incapacity
• Use of notes or aids to support retention is acceptable and should be encouraged
• The MCA explicitly states that a person should not be regarded as unable to understand if they can understand an explanation given in a way appropriate to their circumstances

How to assess: After providing information, return to it later in the consultation and check whether the patient can recall key points. If they cannot, consider whether aids would help.

Example questions: - "We discussed the risks of this procedure earlier — can you remember what they were?" - "What were the main options we talked about?" - "Could you remind me what we said about what happens if you don't take the medication?"

Clinical tip: If a patient with dementia can understand information when it is given but forgets it within minutes, this may affect their ability to retain. However, consider whether using written prompts or having a family member present to remind them would be sufficient support (Principle 2).

3. Weigh or Use the Information

Can the patient weigh the information as part of the decision-making process? This involves:

• Being able to balance pros and cons
• Being able to consider the information in relation to their own values and circumstances
• Not being unduly influenced by abnormal mental processes (e.g., delusions, severe depression, compulsive urges)

How to assess: Explore how the patient is thinking about the decision. Ask about their reasoning process. Listen for whether their reasoning connects the information to their values and circumstances, or whether it is driven by pathological beliefs.

Example questions: - "How have you been thinking about this decision?" - "What factors are most important to you in making this choice?" - "Can you tell me the advantages and disadvantages as you see them?" - "Some people in your situation might be concerned about X — how do you see that?"

This is often the most nuanced criterion. A patient with anorexia nervosa may understand and retain that they are dangerously underweight and could die, but be unable to weigh this information because their disorder prevents them from giving weight to the consequences — the drive to restrict overrides rational weighing. Similarly, a patient with psychotic depression may understand treatment information but be unable to weigh it because a nihilistic delusion makes recovery seem impossible.

4. Communicate the Decision

Can the patient communicate their decision? This can be by any means:

• Talking
• Using sign language
• Writing
• Using communication aids
• Simple gestures (e.g., blinking, squeezing a hand)

How to assess: Ensure you have explored all possible means of communication. Involve speech and language therapists if needed. This criterion is rarely the sole reason for incapacity — it typically applies in cases of severe physical disability, locked-in syndrome, or disorders of consciousness.

Important: A fluctuating or ambivalent decision is not the same as being unable to communicate one. People are allowed to change their minds.

Conducting the Assessment

Opening the Station

1. Introduce yourself and clarify your role
2. Explain the purpose of the assessment: "I'm here to discuss [specific decision] with you and to understand how you're thinking about it"
3. Ensure the patient is comfortable and the environment is suitable
4. Acknowledge that this might feel like an unusual conversation: "I need to ask you some questions about this decision to make sure we're supporting you properly"

Providing Information

5. Provide clear, accessible information about the decision — this is your legal obligation under Principle 2 6. Use simple language, avoid jargon 7. Check understanding as you go: "Does that make sense so far?" 8. Offer information in different formats if helpful 9. Cover: the nature of the decision, the options, the consequences of each option, and the consequences of not making a decision

Assessing the Four Stages

10. Systematically assess each of the four functional criteria 11. Ask the patient to explain information back in their own words — don't just ask "Do you understand?" 12. Explore their reasoning process thoroughly 13. Allow time — don't rush the assessment 14. If the patient appears to lack capacity on one criterion, still assess all four — document your findings comprehensively

Forming a Conclusion

15. Weigh all the evidence — remember the balance of probabilities (more likely than not) 16. Remember: the patient only needs to fail on ONE of the four functional criteria to lack capacity for that decision 17. Consider whether timing or circumstances could be optimised (e.g., reassess when less sedated, when interpreter is available) 18. Identify the causal link between the impairment and the inability

Closing the Station

19. Summarise your findings to the patient 20. Explain your conclusion clearly and sensitively 21. If capacity is lacking, explain next steps (best interests process) 22. If capacity is present, respect their decision even if you disagree 23. Thank the patient

Worked Example: Capacity to Refuse Treatment

Scenario: Mr Ahmed, 45, has been admitted with a relapse of paranoid schizophrenia. He is refusing antipsychotic medication, saying he doesn't need it. You are asked to assess his capacity to refuse treatment.

Stage 1 — Diagnostic threshold: Mr Ahmed has a diagnosis of paranoid schizophrenia — this constitutes an impairment of the mind.

Stage 2 — Functional test:

Understand: You explain that he has been admitted because his family and GP are concerned about his behaviour; that his doctors believe he has schizophrenia, which is a mental illness affecting his thinking; that antipsychotic medication can help reduce the symptoms; and that without treatment, his symptoms may continue or worsen. You ask him to explain this back. He says: "You think I have schizophrenia, and you want me to take tablets." This suggests some understanding, though perhaps limited.

Retain: When you return to this topic later in the assessment, he can recall that you discussed medication. Retention appears adequate.

Weigh: You ask him to consider the advantages and disadvantages of taking the medication. He says: "There are no advantages because there's nothing wrong with me. The voices are real people spying on me — I don't need medication because I'm not ill." His persecutory delusions prevent him from weighing the information — he cannot give weight to the possibility that he has an illness, and therefore cannot meaningfully weigh the benefits of treatment against the risks.

Communicate: He clearly communicates his decision — he does not want medication.

Conclusion: Mr Ahmed can understand, retain, and communicate, but he is unable to weigh the information because his delusional beliefs prevent him from accepting the possibility that he is unwell. His paranoid schizophrenia (the impairment) is the cause of his inability to weigh (causal link). On the balance of probabilities, he lacks capacity to make this specific decision at this time.

Next steps: Best interests decision regarding treatment. Consider whether the Mental Health Act provides a more appropriate framework (if he is detained, MHA provisions may apply to treatment under Part 4).

Documenting Your Findings

In the CASC exam, you may be asked to present your findings to an examiner in a linked station. Structure your documentation as follows:

Template for Documenting a Capacity Assessment

1. The decision: Clearly state the specific decision being assessed (e.g., "Capacity to refuse treatment with olanzapine")
2. The diagnostic threshold: Name the impairment or disturbance (e.g., "Mr X has a diagnosis of paranoid schizophrenia, which constitutes an impairment of the mind")
3. Information provided: What information did you give the patient about the decision? (This demonstrates you fulfilled Principle 2)
4. Understand: What did the patient demonstrate they understood? Quote their words where possible.
5. Retain: Could they retain the information? Over what period? Were aids offered?
6. Weigh: How did they reason about the decision? What interfered with weighing (if applicable)? Quote their reasoning.
7. Communicate: Could they communicate their decision? By what means?
8. Conclusion: "On the balance of probabilities, [Mr/Ms X] does/does not have capacity to [specific decision] at this time, because [reasoning]"
9. Recommendations: Reassessment timescale, best interests process if lacking capacity, optimisation measures

Common CASC Capacity Scenarios

Treatment Decisions

• Capacity to consent to medication (e.g., antipsychotics, ECT, clozapine)
• Capacity to refuse treatment — particularly common when a patient has delusional reasons for refusal
• Capacity to consent to hospital admission (voluntary vs involuntary)
• Capacity to consent to nasogastric feeding in anorexia nervosa

Discharge and Accommodation

• Capacity to make decisions about where to live (e.g., a patient with dementia whose family wants them in a care home)
• Capacity to return home against medical advice
• Capacity to accept or refuse care packages
• Capacity to decide to leave a rehabilitation placement

Financial and Legal Decisions

• Capacity to manage finances (common in dementia stations)
• Capacity to make a will (testamentary capacity — note: this uses a different legal test from Banks v Goodfellow, not the MCA functional test)
• Capacity to grant Lasting Power of Attorney
• Capacity to enter a contract

Personal Welfare

• Capacity to consent to sexual relations (see PC v City of York Council — the assessment is about understanding the act of sexual relations in general, not about a specific partner)
• Capacity to consent to marriage
• Capacity to make decisions about contact with others (e.g., when there are safeguarding concerns)
• Capacity to use social media or the internet

Interaction with the Mental Health Act

A common source of confusion: the Mental Health Act 1983 and the Mental Capacity Act 2005 are separate frameworks. A patient detained under the MHA may still have capacity for many decisions. The MHA provides authority to treat for mental disorder in certain circumstances — this does not depend on a capacity assessment. However, treatment for physical conditions in a detained patient does require either consent (if the person has capacity) or a best interests decision under the MCA (if they do not).

Deprivation of Liberty Safeguards

While full DoLS/LPS (Liberty Protection Safeguards) detail may not be tested in depth at CASC level, you should understand the basic framework:

• If a person lacks capacity and is being cared for in a way that amounts to a deprivation of liberty (continuous supervision, not free to leave), legal authorisation is required
• In hospitals and care homes, this was previously through DoLS (Deprivation of Liberty Safeguards) and is being replaced by LPS (Liberty Protection Safeguards)
• The acid test from Cheshire West (2014): a person is deprived of liberty if they are under continuous supervision and control and are not free to leave, and the person lacks capacity to consent to their arrangements
• In the community, Court of Protection authorisation is needed

In the CASC exam: If a patient lacks capacity to consent to admission, and you conclude they should remain in hospital, mention that a DoLS/LPS authorisation should be considered. This demonstrates awareness of the legal framework beyond basic capacity assessment.

Key Case Law You Should Know

While you won't be examined on case law in detail, knowing key cases strengthens your understanding and impresses examiners:

• Heart of England NHS Foundation Trust v JB (2014): Established that the causative nexus (causal link) between impairment and incapacity must be clearly demonstrated
• PC v City of York Council (2013): Capacity to consent to sexual relations is person-general, not partner-specific — you assess whether the person understands the act of sexual intercourse, the health risks, and the risks of pregnancy
• Kings College Hospital NHS Foundation Trust v C (2015): Reinforced that a person with capacity has the right to make unwise decisions, including refusing life-saving treatment
• Cheshire West (2014): Defined the "acid test" for deprivation of liberty

Communication and Best Interests

If you conclude that the patient lacks capacity:

Communicating the Outcome

• Explain your conclusion sensitively and clearly: "Based on our conversation, I feel that at this point in time, you're not able to fully weigh up the information about this decision because..."
• Acknowledge the patient's feelings — they may feel frustrated, upset, or angry
• Emphasise that the assessment is decision-specific — lacking capacity for one decision doesn't mean lacking capacity for all decisions
• Emphasise that the assessment is time-specific — capacity may be regained, and you will reassess
• Explain what will happen next

Best Interests Decision-Making

Examiners may ask you to explain the best interests process. This is a structured process, not simply a clinical decision:

1. Consider all relevant circumstances — not just the medical facts, but the person's whole situation
2. Consider whether capacity might be regained — can the decision wait? (e.g., a patient who is acutely intoxicated may regain capacity within hours)
3. Encourage participation as far as possible — even if a person lacks capacity for the overall decision, their views still matter
4. Consider the person's past and present wishes, feelings, beliefs, and values — what would they have wanted? Is there an advance decision?
5. Consult relevant others — family, carers, attorneys, deputies, IMCAs (Independent Mental Capacity Advocates)
6. Choose the least restrictive option that achieves the goal

Advanced Best Interests Consultation

Independent Mental Capacity Advocates (IMCAs)

An IMCA must be instructed when: - A person who lacks capacity has no family or friends to consult - AND a decision is being made about serious medical treatment or a change of accommodation

Advance Decisions to Refuse Treatment (ADRT)

If a valid and applicable advance decision exists, it is legally binding. To be valid for life-sustaining treatment, it must be: - In writing - Signed and witnessed - Contain a statement that the decision stands "even if life is at risk"

Lasting Power of Attorney (LPA)

If a health and welfare LPA has been registered and the donor has lost capacity, the attorney can make decisions on their behalf. The attorney must act in the person's best interests.

Court of Protection

For particularly complex or contested decisions, application to the Court of Protection may be necessary. This includes disputes between family members and clinical teams about best interests.

Common Mistakes to Avoid

1. Assuming incapacity based on diagnosis — A psychiatric diagnosis does not automatically mean incapacity. This is the most fundamental error and directly contradicts Principle 1.
2. Conflating unwise decisions with incapacity — Patients have the right to make unwise decisions if they have capacity. An anorexic patient who restricts food may have capacity; a person with depression who refuses treatment may have capacity. Assess the process, not the outcome.
3. Rushing the assessment — Take time to explain information and assess properly. In the CASC, you have 7 minutes — use them well. Don't skip straight to the functional test without first providing information.
4. Not being decision-specific — Capacity must be assessed for the particular decision at hand. "Does this patient have capacity?" is not a valid question — "Does this patient have capacity to refuse olanzapine at this time?" is.
5. Forgetting to provide information first — You must give the patient the information relevant to the decision before testing whether they understand it. Failure to do this invalidates the assessment.
6. Not establishing the diagnostic threshold — Remember to identify the impairment or disturbance first (Stage 1). Without this, the functional test has no legal basis.
7. Not considering optimisation — Could capacity be improved by timing (when less sedated?), environment (quieter room?), support (interpreter, communication aids?), or treatment (treating delirium)?
8. Testing memory rather than understanding — Capacity is not a memory test. If a patient can understand information with support, even if they need reminding, that may be sufficient for the understanding criterion.
9. Forgetting the MHA/MCA interface — For a detained patient who needs treatment for mental disorder, the MHA may be the relevant framework, not the MCA. Demonstrate you know the difference.
10. Not mentioning next steps — If capacity is lacking, the examiner expects you to outline the best interests process. If capacity is present, state that the patient's decision must be respected.

Practice Checklist

• Can I recite the five statutory principles of the Mental Capacity Act with clinical examples?
• Can I explain the two-stage test (diagnostic threshold + functional test) and the causal link between them?
• Can I systematically assess the four functional criteria with appropriate, open-ended questions?
• Can I distinguish between an unwise decision and incapacity?
• Can I document my findings clearly using the structured template and justify my conclusion?
• Can I explain the best interests process, including who must be consulted?
• Can I communicate the outcome of a capacity assessment sensitively to the patient?
• Do I understand the difference between MCA capacity assessment and MHA treatment provisions?
• Can I explain what DoLS/LPS are and when they would apply?
• Do I know the key case law and what each case established?
• Have I practiced capacity assessment stations under timed conditions with a variety of scenarios?
• Can I handle a patient who becomes upset or angry when told they lack capacity?