Ghosts of Capacity: When Mental Capacity Fluctuates

As Halloween approaches, our Court of Protection team is marking the occasion with daily insights into the complexities and challenges of our work.

This week we will be posting short articles that explore key themes in Court of Protection practice with a seasonal theme!

In the Court of Protection, few issues are as complex, or as haunting, as fluctuating mental capacity. Capacity is not a fixed state. It can shift, sometimes subtly and sometimes dramatically, influenced by illness, stress, medication, environment or circumstance.

These fluctuations create what might be called the ghosts of capacity-moments when a person appears to understand, decide and act with clarity, only for that clarity to fade. For practitioners, judges and families, these moments raise profound legal and ethical questions: when is a decision truly the person’s own and when is it a shadow of what once was?

Under the Mental Capacity Act 2005 (MCA), capacity is both decision specific and time specific. A person may have capacity to decide what to eat, but not to manage complex finances. They may have capacity today, but not tomorrow. The Court of Protection’s task is to recognise and respect autonomy where it exists, while safeguarding the individual when it does not. This is a balancing act that becomes especially delicate when capacity fluctuates.

Fluctuating capacity is common in conditions such as bipolar disorder, dementia and certain neurological illnesses. It can also arise with medication changes, infection or acute distress. Courts must consider not only whether someone has capacity, but when, for how long and under what conditions they have this.

Judicial decisions have grappled with these nuances. In Re C (2021), the Court of Protection emphasised that temporary lucidity should not automatically restore full legal capacity if it cannot be reliably sustained. Conversely, in A Local Authority v JB (2020), the Court reaffirmed that the presumption of capacity remains strong, and fluctuation does not justify paternalism. The challenge lies in ensuring protection without extinguishing autonomy. As the courts have noted, a fluctuating capacity is still capacity, when present.

Ultimately, capacity is not an abstract legal construct and credence must be given to its fluidity.

Courts, clinicians, and families must navigate its shifting presence with humility and precision. In every case, the task is not to chase ghosts, but to recognise the living person behind them.

Our specialist Care Funding and Court of Protection team can answer any of your queries relating to mental capacity, the Court of Protection or care funding.