Late Stage Alzheimer's disease is an example of mentally incapacitated.
When a person is mentally incapacitated, it means that the person can't effectively manager their own affairs or even make their own sound decisions regarding their finances, health, or even legal obligations as a result of a cognitive impairment.
Someone with late stage Alzheimer's disease cannot understand legal contracts or properly care for themselves or even a person in a coma after a traumatic brain injury is another example of someone being mentally incapacitated.
There's also permanent and temporary mental incapacitation depending on the illness or cause.
For example, conditions like Alzheimer's disease or Huntington's disease result in an irreversible and permanent decline in a persons mental function.
And being placed under general anesthesia during surgery, falling unconscious from a severe fall or experiencing temporary drug induced delirium can cause someone to become temporarily mentally incapacitated.
Incapacitation and Incompetence are also often used interchangeably although they have distinct legal meanings.
Being incapacitated is usually the mental or physical inability to manage their own daily affairs and incompetence is a formal legal finding by a judge that removes a person's legal rights, often requiring the appointment of a legal guardian.
And to sign a document that is legally binding, like a will, power of attorney or even a trust, a person must possess the mental capacity to be able to understand what they are signing and it's consequences of signing the document.
If a person has advanced dementia and can no longer recognize their assets or even comprehend the purpose of a will, then they are legally incapacitated.
And so consequently, any legal documents that they attempt to sign can be invalidated by a court.
Or when a person suffers from a severe mental illness, an intellectual disability or a stroke that prevents the person from grasping their medical needs, they are not able to provide informed consent for treatments and in these situations, surrogate decision makers, like an appointed agent on a healthcare proxy or even a court appointed guardian are required to make choices on their behalf.