I am going through a will challenge where my brother has used the medical notes of my late father's physician to overturn changes he made to his estate plan. I expect the doctor to defend his notes, realizing now that he discounted dad's capacity without ever giving him a chance to prove himself.
dementia is a medical diagnoses , but that dx doesnt stop an elder from managing their own business ..
Have you contacted the attorney who made the changes to determine if there was any indication during the signing that your father wasn't capable of understanding what he was doing?
Are the changes to the estate plan outrageous? Did he change from leaving his estate to his relatives to dropping dollar bills out of a helicopter during a state fair? Are the changes in nature of things Dad would never have done "in his right mind"?
I hope you have a lawyer to represent your interests.
I don't really see any point in tell a doctor his DX was half-baked; I'd focus on written documentation to contest the will challenge.
It wouldn't hurt to document, if you have access to the financial records, the substantial sums of money already given to your brother.
Same with the behavior after your mother's death.
All of this will help build the case that your brother expects a given amount, when in reality the inheritance decisions are those of your father. A mistake I think a lot of adult children make is assuming that they're entitled to something regardless of help and/or behavior for their parents.
The fact that the doctor only saw your father for a short time will diminish the efficacy of his conclusions, especially if the other regularly treating doctors didn't make the same conclusion.
I want to thank you also for sharing this personal aspect of your family's life as it's given me some thoughts on what I may eventually have to deal with as well.
I know this is possible but its just so funny the image of him in that helicopter!!