The Role of Capacity Evidence in Best Interests Decisions

The Court of Protection plays a vital role in safeguarding individuals who lack the mental capacity to make decisions for themselves. Operating under the Mental Capacity Act 2005, the Court determines whether a person can make a specific decision and, if not, makes that decision on their behalf in their best interests.

Capacity is both decision-specific and time-specific and there is a statutory presumption of someone having capacity unless proven otherwise. When a person is found to lack capacity, the Court must then undertake a best interests analysis, balancing medical, social and personal factors to reach an outcome that respects P’s welfare, rights and values. A central component of this process is capacity evidence, particularly from expert witnesses.

The Importance of Expert Evidence

Expert evidence, typically from psychiatrists, psychologists and/or qualified social workers, is often critical in Court of Protection proceedings. Experts assess whether P can:

• Understand relevant information;
• Retain it;
• Use or weigh it; and
• Communicate a decision.

Such evidence assists the court by providing clinical insight into P’s condition, by identifying the information relevant to the decision, including foreseeable consequences and then by offering an opinion on whether any inability is caused by an impairment of the mind or brain.

However, expert evidence is not determinative. The court is the ultimate decision-maker and must weigh expert opinion alongside all other evidence. A failure by an expert to address key matters, particularly the consequences of a decision, can significantly undermine the weight of their conclusions.

Case Example: Camden London Borough Council v BW[1]

BW was a 27-year-old woman with autism and a complex history of vulnerability, including exploitation, mental health crises and hospital admissions. The proceedings concerned her capacity to:

1. Decide whether to take psychotropic medication; and
2. Decide whether information should be shared with her sister (AW).

An expert psychiatrist initially concluded that BW had capacity in both areas however the Court of Protection made a finding that BW lacked capacity and made a best interests on behalf of BW.

Reason for the Appeal

[1] [2026] EWCOP 26

The local authority appealed the first instance decision on several grounds, primarily arguing that the judge:

• Failed to provide adequate reasons on capacity; and
• Wrongly departed from the expert evidence.

The appeal was dismissed and the Court upheld the trial judge’s finding that BW lacked capacity, despite the expert’s opinion to the contrary.

The key issue was whether the expert had failed to consider critical “reasonably foreseeable consequences” of BW’s decisions, as required under s.3(4) MCA. In particular:

• He did not address that refusing medication risked loss of BW’s placement, which could have severe consequences given her history; and
• He did not explore the impact of refusing to share information with AW, including the potential loss of crucial advocacy and support.

The Court held that these omissions were fundamental. Without considering such consequences, BW could not properly understand or weigh the relevant information, meaning she lacked capacity.

Importantly, the Court reaffirmed that:

• Judges may depart from expert evidence where there is a clear evidential basis; and
• The focus must remain on the statutory test, not the expert’s conclusion.

This case provides several important lessons for practitioners:

1. Foreseeable consequences are central. Capacity assessments must address real-world outcomes of decisions. Omitting significant consequences can render an expert opinion unreliable.
2. Expert evidence must be decision specific. Generalised assessments are insufficient—experts must engage with the specific factual context of the decision.
3. The court is not bound by the expert. Expert evidence is influential but not decisive. Judges will depart from it where necessary to apply the MCA test correctly.
4. Capacity is distinct from welfare. The court must avoid the protection imperative. Capacity cannot be denied simply because a decision appears unwise. However, failure to grasp consequences is a legitimate basis for finding incapacity.
5. Comprehensive evidence is essential for best interests decisions. Robust capacity evidence ensures that, where capacity is lacking, the court can confidently move to a best interests determination grounded in a full understanding of P’s situation.