If parent is diagnosed with dementia, are any legal papers signed by the parent after the diagnosis legal and binding?

Much of that depends on their stage of dementia at diagnosis. If you need legal papers drawn up, do it immediately with an attorney who can check state laws. A doctor's opinion may be required.
Take care,
Carol

It doesn't matter what type of lawyer it was. If she had beginning stages of dementia and two witnesses should have had to sign the document then it should be valid. Does she know who you are, where she lives, does she take care of herself with hygeine, eats meals and just has some short term memory loss? If yyou answered yes to these questions she is capable of signing papers. If she is totally out of it and does not remember anyone or anything from one minute to the next then she can't really sign for anything. Has she been diagnosed by a physician who says she has dementia? There has to be some kind of documentation somewhere that says she is incapable of making sound decisions and would have had to had tests done by a doctor to determine that. Hope this helps you a little bit to understand what needs to be done to get a better determination of dementia.

What if the attorney who was used was a bankruptcy atty and admitted he was probably not very 'up' on his elder law?

NoVoice,
This is a scary question. Has your mom actually signed any significant documents? If so, remember that as far as I know an active membership in the Bar association is sufficient to draft any and all types of legal documents. Your Bankruptcy lawyer is really setting him or her self up fo a nasty malpractice claim if he accepted the responsibility to do a job about which he was admittedly unqualified. I certainly hope that no actual damages have occurred because of this error.