Who Can Carry Out a Mental Capacity Assessment? A Definitive Guide for UK Medico-Legal Practice

In clinical negligence claims, personal injury litigation, and inquest proceedings, the question of who can assess mental capacity frequently arises. The assessment is governed by the Mental Capacity Act 2005 (MCA 2005) and its accompanying Code of Practice. This framework establishes both the legal standards for capacity and the professional qualifications required. For solicitors, barristers, and medico-legal experts, understanding these requirements is critical to ensuring evidence is robust, admissible, and capable of withstanding scrutiny under Bolam v Friern Hospital Management Committee [1957] and Bolitho v City and Hackney Health Authority [1998].

The Legal Framework Under the Mental Capacity Act 2005

The MCA 2005 provides the statutory basis for determining whether an individual has capacity to make a specific decision at a specific time. Capacity is decision-specific; an individual may have capacity for some decisions but not others. The Act sets out a two-stage test:

1. Diagnostic test: Does the person have an impairment of, or disturbance in the functioning of, the mind or brain?
2. Functional test: Does this impairment mean the person is unable to make the decision in question?

The functional test requires the person to understand, retain, use or weigh relevant information, or communicate their decision. The MCA 2005 establishes the principle that a person must be assumed to have capacity unless proven otherwise. This presumption is fundamental in medico-legal practice, particularly where capacity is contested.

Qualified Professionals for Mental Capacity Assessments

The MCA 2005 does not prescribe a specific professional group as the sole authority. Instead, it states anyone can assess capacity if they possess the necessary skills, knowledge, and experience. In practice, the following professionals are commonly involved:

• Psychiatrists: Consultant psychiatrists, particularly those specialising in old age, forensic, or neuropsychiatry, are frequently instructed. Their expertise is relevant in cases involving dementia, acquired brain injury, or complex mental health conditions. In clinical negligence claims, they may opine on whether a patient had capacity to consent to treatment.
• Neurologists: In cases involving traumatic brain injury, stroke, or neurodegenerative conditions, a consultant neurologist may be appropriate. They assess the impact of structural brain abnormalities on cognitive function.
• Clinical Psychologists: With expertise in neuropsychological assessment, they evaluate cognitive function using standardised tools. Their input is valuable where capacity is borderline, though they do not diagnose mental disorders.
• Geriatricians: In cases involving older adults, particularly those with frailty or multiple comorbidities, they assess capacity. Their expertise in the interplay between physical and cognitive decline is pivotal.
• General Practitioners: While GPs may undertake assessments in primary care, their role in medico-legal contexts is limited due to potential lack of specialist expertise. However, their contemporaneous records may be critical.
• Other Specialists: In specific contexts, consultants in learning disabilities or paediatricians (for those under 16) may assess capacity.

Medico-Legal Considerations in Capacity Assessments

In clinical negligence claims, capacity assessments often arise in the context of consent to treatment. Montgomery v Lanarkshire Health Board [2015] established that clinicians must ensure patients understand material risks. Where capacity is in doubt, a formal assessment may be required. Failure to assess capacity appropriately can constitute a breach of duty.

Key considerations include:

• Contemporaneous Records: Experts require all relevant medical records, including prior capacity assessments and cognitive screening tools (e.g., Montreal Cognitive Assessment). These establish baseline cognitive function.
• Subspecialty Matching: The choice of expert is critical. For example, a neuropsychiatrist may be better suited than a general psychiatrist for traumatic brain injury cases. Multi-disciplinary chambers can provide matched subspecialist expertise.
• Joint Statements and Single Joint Experts: Under CPR Part 35, experts have a duty to the court. In disputed cases, the court may order a Single Joint Expert or joint statement. Chambers offering multiple specialties can facilitate coherent joint statements.
• Causation and Loss of Chance: Experts must address causation where lack of capacity assessment is alleged to have led to harm. Principles from Bailey v Ministry of Defence [2008] may apply where multiple factors contribute.

Common Pitfalls in Capacity Assessments

Disputes over mental capacity are common in clinical negligence claims. Key issues include:

• Retrospective Assessments: Challenging due to reliance on records and witness statements. Experts must determine what was reasonably ascertainable at the time.
• Fluctuating Capacity: Conditions like delirium may cause capacity to vary. Experts must analyse the clinical timeline to determine capacity at the specific decision time.
• Disputes Over the Functional Test: Disagreements arise over whether the patient could have understood information if presented differently. Experts may need to opine on the adequacy of information provided.
• Conflicts in Evidence: Contemporaneous records may conflict with retrospective evidence. Experts must reconcile discrepancies and provide a reasoned opinion.
• Inappropriate Expertise: Instructing an expert without relevant subspecialty can weaken evidence. Multi-disciplinary chambers mitigate this risk by providing matched expertise.

The Role of the Expert Witness

The expert witness must address key questions in their report:

• Did the patient have an impairment of the mind or brain at the relevant time?
• Did this impairment render the patient unable to make the specific decision?
• Was the assessment conducted in accordance with the MCA 2005 and clinical guidelines?
• What would have been the likely outcome if capacity had been assessed appropriately?

The report must be clear, evidence-based, and compliant with CPR Part 35. It should avoid speculative language and outline limitations where evidence is insufficient.

Practical Guidance for Solicitors

For solicitors instructing experts, the following steps are recommended:

1. Identify the Relevant Subspecialty:
   • Traumatic brain injury or stroke: Neurologist or neuropsychiatrist.
   • Dementia: Old age psychiatrist or geriatrician.
   • Mental illness: Consultant psychiatrist.
   • Learning disabilities: Consultant in learning disabilities.
2. Provide Comprehensive Records:
   • Contemporaneous capacity assessments.
   • Mental health assessments.
   • Cognitive screening tools (e.g., MoCA, ACE-III).
   • Witness statements.
3. Clarify the Scope of Instruction:
   • Assess capacity retrospectively.
   • Evaluate the adequacy of a contemporaneous assessment.
   • Address causation.
4. Consider Multi-Disciplinary Input: Complex cases may require input from multiple specialties. Multi-disciplinary chambers can streamline this process.
5. Prepare for Joint Statements: Experts must be prepared to engage in joint statements under CPR Part 35.

Conclusion

The question of who can assess mental capacity is central to many clinical negligence claims. While the MCA 2005 does not prescribe a specific professional group, the assessment must be undertaken by an expert with appropriate skills and experience. Subspecialty matching strengthens evidence, particularly in complex cases.

For legal practitioners, understanding the nuances of capacity assessments and the role of expert witnesses is essential. By instructing the right subspecialist and providing comprehensive records, solicitors can ensure robust, admissible evidence. Multi-disciplinary chambers offering matched expertise are pivotal in such cases.