Speaking generally, (not particularly about Bob) an assertion of someone's mental health, whether by a friend, relative or doctor, would never hold up in a court of law. Just because someone can carry on a conversation, or pay bills it doesn't necessarily mean they are mentally stable. It's much more complicated than that.
From one website: The diagnosis of dementia requires a complete medical and neuropsychological evaluation.
There are all kinds of specific tests, which are administered by more than one doctor, that would determine dementia, competency or other life altering mental issues.
I know several people who have, or actually died from dementia. Most mental illnesses associated with old age come on slowly. I interact with one neighbor on a regular basis. Over time, she was diagnosed with dementia. But it's by far not the only mental problem that afflicts people, in particular the elderly.
Mental health problems related to age, are exactly why elder abuse is so common. Although they need someone to look out for their well being, the elderly also become paranoid, argumentative, stubborn. This is not just my opinion, either. These are facts in the same way that adolescents usually have skin problems. It's not everyone, but a large majority.
Calling for a welfare check on their father is exactly what the daughters should have done when they found out about the hairdresser. But I think they should have called social services since the police are usually not educated about these things. If these incidents were not reported, and Bob's bank account had been wiped out by the hairdresser or someone else, the daughters could have been cited for neglect in the care of a parent. Sometimes you just can't win.
