Identifying Confirmation Bias in Capacity Assessments for the Court of Protection

The Challenge of Neutrality in Capacity Assessments

In proceedings before the Court of Protection, the reliability of a neurological capacity assessment is contingent upon the expert’s clinical objectivity. Confirmation bias—the cognitive tendency to prioritise information that supports an initial hypothesis while discounting contradictory evidence—presents a material risk to the validity of an expert report. Instructing solicitors and counsel play a critical role in framing the scope of instructions to help ensure that evidence remains compliant with the Mental Capacity Act 2005 (MCA) and withstands rigorous adversarial scrutiny.

Neurological Complexity and Cognitive Priming

Capacity assessments are typically informed by extensive background documentation, including GP records, witness statements, and previous neurological history. While such data is necessary to establish the clinical context—such as the presence of a Traumatic Brain Injury (TBI), neurodegenerative decline, or stroke-related deficits—this preparatory material may inadvertently prime an expert toward a specific conclusion.

For example, if a clinician reviews evidence suggesting frontal lobe pathology, they may adopt a working hypothesis of executive dysfunction. If the assessment protocol is not carefully structured, the expert might focus exclusively on confirming deficits consistent with that hypothesis, while failing to evaluate preserved functional abilities. A more robust approach involves an iterative process: establishing the clinical findings through formal testing and then actively testing alternative hypotheses, including the possibility that the individual retains the capacity to make the specific decision at issue.

Methodological Safeguards

Under CPR Part 35.3, an expert witness holds an overriding duty to the court to provide independent and objective evidence. To mitigate the risk of bias, neurology experts are encouraged to adopt structured assessment methodologies.

• Functional Task Analysis: Deconstructing the decision-making process into the specific requirements of the MCA—understanding, retaining, weighing, and communicating information—relative to the specific decision in question.
• Symptom Validity Testing: In cases involving complex clinical presentations, such as Functional Neurological Disorder (FND), objective testing for symptom validity may assist in distinguishing organic neurological pathology from other presentations.
• Longitudinal Review: Contrasting current functional performance against pre-morbid baseline data, such as employment history, modified Rankin Scale scores post-stroke, or documented cognitive markers prior to a diagnosis of a neurodegenerative condition.

The expert’s report should distinguish clearly between the clinical diagnosis and the functional consequence. An expert opinion should address how specific neurological sequelae impact the ability to perform the statutory test under the MCA, ensuring the analysis is grounded in evidence rather than anecdotal observation.

Managing Diagnostic Overreach and Causation

A frequent area of medico-legal dispute involves the attribution of cognitive impairment to a specific event versus pre-existing conditions. Confirmation bias can manifest as ‘causation creep,’ where an expert attributes all observed deficits to an index injury, potentially overlooking pre-existing comorbidities that would be identified through a thorough differential diagnosis.

When assessing capacity in the presence of complex symptoms, experts must be cautious of diagnostic overreach. For instance, in a patient with epilepsy, it is necessary to differentiate the transient effects of seizure activity or post-ictal states from underlying cognitive decline. Failing to account for such fluctuations—or the impact of polypharmacy on cognitive speed—can lead to an inaccurate assessment. Solicitors may assist by ensuring that instructions invite the expert to consider the full range of potential aetiologies for the observed neurological condition.

Practical Considerations for Instructing Solicitors

Solicitors play a significant role in managing the scope of instructions to foster objectivity. To ensure an expert provides a report that is consistent with the requirements of professional capacity assessment standards, consider the following:

• Specific Decision Framing: Ensure the expert is assessing capacity regarding the specific decision mandated by the Court of Protection (e.g., property and affairs, health and welfare). Capacity is decision-specific and not a global status.
• Balanced Documentation: Provide a representative set of records. If the provided documentation contains only evidence supporting incapacity, the expert’s ability to remain impartial may be compromised.
• Methodological Inquiry: Invite the expert to describe their method for identifying and excluding cognitive biases, particularly in cases where the clinical presentation is ambiguous.
• Timing of Assessment: Ensure the assessment timing aligns with the client’s stable state, avoiding periods of acute medical crisis which may cause transient, non-representative impairment.

The appointment of a neurological expert for a capacity assessment should reflect their capacity to apply a rigorous, evidence-based methodology to the statutory requirements of the MCA. By focusing on the structural components of the capacity test and demanding transparent reasoning, legal professionals can better protect the integrity of the evidence presented before the Court of Protection.