It’s not always clear when someone’s lost the ability to decide

May 23, 2026 - 12:09

It is rarely a clean break when a person loses the capacity to make their own decisions. Unlike a light switch that flips from on to off, the decline in cognitive function is often a slow, uneven process. This reality creates profound challenges for families and the legal system, especially when trying to determine if a person with dementia can still make a valid choice.

The legal concept of a "lucid interval" complicates matters further. This term describes a temporary moment of clarity where a person who is generally confused might suddenly seem fully aware and capable. A patient might sign a contract or change a will during one of these windows, only to return to a state of confusion an hour later. The problem is that proving a lucid interval existed after the fact is extremely difficult. Memory is subjective, and witnesses may disagree on whether the person truly understood the consequences of their actions.

For families, this uncertainty is a source of deep anxiety. A loved one might insist they want to move to a new city one day, then forget the conversation the next. Without clear legal documents like a durable power of attorney for healthcare and finances, families can end up in costly court battles to establish guardianship. Experts stress that the time to plan is early, while the person can still express their wishes clearly. Waiting until the line of capacity is blurred only invites confusion and conflict, leaving the most vulnerable person without a voice when they need one most.