At what point is someone deemed not of sound mind?

One thing you must look at is what do the documents say. Is there the word "incapacitated" or is it "disabled" ? There is a difference. Also, is the power of attorney in effect not (effective) or only about disability or incapacity (springing)? There is not a bright-line on these questions and there really is no way for there to be such a clear determination but that is why it would be helpful to have an attorney and then possibly other professionals to evaluate her.

Hello, In addition, you may want to get an opinion from a doctor as to her mental capacity.

The California Probate Code has a relatively low bar for deeming someone to be incapacitated. Basically, It assumes a person to have capacity if they know who they are; know who there family relations are; and understand the ramifications of their actions. A diagnosis of dementia or Alzheimers does not necessarily make a person incompetent, as people sometimes have moments of clarity despite their diagnosis. However, these people still might be subject to undue influence, fraud, elder abuse, etc. The Trust may have a definition of what is deemed incapacity, such as a Treating Physician stating that the person is incapable of making such decisions or managing their affairs. I would read the Trust for this language, but in any event, have her evaluated. The best one to evaluate her would be a geriatric neuropsychiatrist.

That's a medical question. Hence can't be answered here.

Attorney Mchughes' response appears to be on point in answering your questions. However, you state that your mother's understanding and thought process seems to be very sharp. This is a good indication that she has capacity to sign a durable power of attorney with the requisite understanding. As regards your father's powers of attorney, they died with him. Your mother's health care directives are hers to cancel and make new ones as long as she understands the effect of her actions. If she knows who her children are and what she owns, she has testamentary capacity to make a will. If she can understand that effect of the terms of a trust she would probably be found to have capacity to make or amend a trust (if the trust terms allow an amendment). I hope this helps. Given your concerns, you should urge mom to consult with an attorney when she seeks to make any changes, amendments or new documents. Do not let her proceed on a "do it yourself" basis to avoid later difficulties for her heirs/beneficiaries. Her personal physician should also be consulted regarding her capacity since he will be the medical provider who knows her over the longest period of time and can evaluate changes in her mental state.