Doesn't it involve certification by a physician? There's probably some subjectivity there.. I don't know if there are standards.
I'm sure you've already researched, but here's one site with some information:
https://www.agingcare.com/articles/w...ile-441176.htm
If you're looking for personal experience, when my mother had her aneurysm/stroke, she went from being a fully functional 50 year old to not knowing what planet she was on. It was heartbreaking, but she wound up in a nursing home. When I asked her doctor about her prognosis, her curt reply was "they usually stay that way." So there she was, missing out on enjoying her first grandson who had been born just two weeks after her event.
God sent an angel in the form of a friend of hers who would take her out to lunch once a week--despite my mother's confusion and disorientation. She noticed that some days she was perfectly lucid, and other days she would spoon her ice cream into her tea and talk about General Patton walking the halls. So she told me that she thought my mother should get re-evaluated.
So my mother's other best friend and I took her to Gaylord in New Haven, and she underwent a batter of tests there, and based on that, the doctor told the nursing home to stop giving her any medication.
Within a week my mother "woke up"--it was literally like the movie Awakenings. After 18 months lying in a nursing home bed, she became herself exactly as if she came out of a coma. She asked me what happened to this? How is so-and-so?
Not sure how this relates to your specific situation, Tybee, but I guess I would say that getting your mother evaluated by the most credible institution you can find would give you some confidence in their ability to certify your mother's capacities.