The Mental Health Act 1983 and Mental Capacity Act 2005 appear consistently across MRCPsych Paper B, CASC, and clinical practice. The exam questions are often high-stakes because the legal framework is non-negotiable — getting an MHA section wrong is the difference between lawful detention and false imprisonment.
This guide covers the essential legal knowledge for Paper B, structured the way the exam tests it.
MHA 1983 — The Core Sections
Civil Detention
Section 2: Admission for assessment. Duration: up to 28 days. Grounds: (a) the patient is suffering from a mental disorder of a nature or degree that warrants detention for assessment, AND (b) detention is necessary for the health or safety of the patient or the protection of others. Cannot be renewed — must be converted to S3 or the patient discharged.
Section 3: Admission for treatment. Duration: up to 6 months, renewable. Grounds: (a) the patient is suffering from a mental disorder of a nature or degree that makes treatment in hospital necessary, AND (b) appropriate medical treatment is available, AND (c) detention is necessary for health/safety or protection of others. Requires two doctors (S12-approved + one other) and an AMHP.
Section 4: Emergency admission. Duration: up to 72 hours. Grounds: urgent necessity where compliance with S2/S3 procedures would cause undesirable delay. One doctor (any), one AMHP (or nearest relative). Cannot be renewed — must be converted to S2 or S3.
Section 5(2): Doctor’s holding power. Duration: up to 72 hours. Used when an informal inpatient decides to leave and is at risk. The responsible clinician or their nominated deputy can detain. Nominated deputy is usually the duty doctor — not any doctor.
Section 5(4): Nurse’s holding power. Duration: up to 6 hours. Used when a doctor is not immediately available. The nurse must be of a prescribed class (RMN or RNLD).
Community Powers
Community Treatment Order (CTO — S17A): Allows supervised treatment in the community for patients previously detained under S3. Conditions can include: residence, attending appointments, taking medication. Recall to hospital if conditions are breached. Renewable annually.
Section 17 Leave: The responsible clinician can grant leave of absence to a detained patient. Can be for any period but requires renewal if >7 consecutive days in the first month. Leave can be escorted or unescorted and can include conditions.
Forensic Sections
Section 37: Hospital order (court). The court makes an order for detention in hospital following conviction for an imprisonable offence (excluding murder, where S41 is mandatory). Requires two doctors to confirm that detention is necessary.
Section 41: Restriction order. Imposed by the Crown Court alongside S37 (or S47) to protect the public from serious harm. Unrestricted or restricted (by time, conditions, or absolute). Discharge requires Secretary of State or Mental Health Tribunal approval.
Section 47/49: Transfer of prisoners to hospital for treatment. S47 is the transfer direction; S49 imposes restrictions equivalent to S41.
Section 48/49: Transfer of unsentenced/remand prisoners. S48 is the transfer direction for urgent cases.
Treatment Provisions
Section 57: Neurosurgery for mental disorder. Requires consent + SOAD + independent panel. Very rarely used.
Section 58: Medication beyond 3 months. Requires either the patient’s consent OR a SOAD (Second Opinion Appointed Doctor). This is the most commonly examined treatment section.
Section 58A: ECT. If the patient has capacity and consents: requires consent + SOAD confirmation. If the patient lacks capacity OR refuses: requires SOAD + the treatment must be immediately necessary to save life or prevent serious deterioration.
Section 63: Treatment not requiring consent. Covers treatments not covered by S57/58/58A (nursing care, rehabilitation, oral medication within the first 3 months).
MCA 2005 — The Five Principles
The MCA is organised around five statutory principles. The exam expects you to know them in order and understand their application:
- Presumption of capacity: Every adult has the right to make their own decisions unless proven otherwise.
- All practical steps: A person should be supported to make their own decision before concluding they lack capacity. This includes communication aids, interpreters, timing, and environment adjustments.
- Unwise decisions: A person is not to be treated as lacking capacity merely because they make an unwise decision.
- Best interests: Any act or decision made on behalf of a person who lacks capacity must be in their best interests.
- Least restrictive intervention: Before acting, consider whether the purpose can be achieved in a way that is less restrictive of the person’s rights and freedoms.
The Two-Stage Capacity Test
Diagnostic test (Stage 1): Is there an impairment of, or disturbance in, the functioning of the mind or brain?
Functional test (Stage 2): Does the impairment mean the person cannot:
- Understand the relevant information, OR
- Retain that information, OR
- Use or weigh that information, OR
- Communicate their decision?
The capacity assessment is decision-specific and time-specific. A person may have capacity to decide what to eat but not to decide about a complex treatment. A person who lacks capacity today may regain capacity tomorrow.
The MHA vs MCA Interface (Most Examined Area)
This is the most commonly tested legal question in Paper B. The key distinctions:
| Scenario | Use MHA | Use MCA |
|---|---|---|
| Objecting to admission for mental disorder treatment | S2/S3 | No — cannot deprive of liberty under MCA if objecting (unless DOLS/LPS process) |
| Lacks capacity + non-objecting + requires care in a care home | No | DOLS/LPS authorisation |
| Lacks capacity + non-objecting + requires hospital admission | No (if no objection) | S4B (urgent) then Court of Protection (standard) |
| Has capacity + refusing treatment + meets MHA criteria | S2/S3 | No — cannot treat under MCA if person has capacity |
| Physical health treatment for a detained patient who lacks capacity | No (MHA covers mental disorder only) | MCA — best interests decision |
Liberty Protection Safeguards (LPS)
LPS replaces DOLS from April 2025 (implementation now phased). Key changes:
- Applies to 16–17-year-olds as well as adults
- Three assessments: capacity, medical, and necessary and proportionate
- The responsible body (ICB or Local Authority) arranges the assessments, not the court
- Duration: up to 12 months (renewable), compared to DOLS 12 months (non-renewable for care homes)
Exam Question Patterns
Legal questions in Paper B tend to follow predictable patterns:
- “A 45-year-old woman with schizophrenia refuses medication. She has insight. Her PHQ-9 is 9. What is the next step?” — Answer: She has capacity and is not at imminent risk. You cannot force treatment. Offer alternatives, negotiate, and monitor.
- “A 68-year-old man with dementia is refusing care in a care home. He cannot understand the risks. What legal framework?” — Answer: MCA capacity assessment. If lacks capacity and is objecting, DOLS/LPS authorisation is needed for the deprivation of liberty.
- “Which MHA section allows ECT when the patient refuses?” — Answer: S58A (requires SOAD + urgency).
- “How long can a nurse hold a patient under S5(4)?” — Answer: 6 hours.
PsychStar’s Paper B bank includes dedicated legal questions with full teaching cascades covering MHA/MCA case law. Try 5 free questions at psychstar.io/try.