Capacity to make will;Medical evidence is not last word
In matters of mental capacity, the evidence of doctors is often conclusive. It is not often that the opinion of a lawyer about mental capacity trumps that of a doctor, and rightly so, since doctors applying scientific diagnostic criteria and experience have the expertise to properly answer questions about mental capacity. However, in some situations, a Court may prefer non-expert evidence of capacity to the extent it is focused on a particular issue, supported by outside evidence, and benefits from a particular legal test for mental capacity.
In Moore v. Drummond, handed down by the British Columbia Supreme Court in November of last year, this is exactly what the court did. The deceased, Ms. Drummond, had made a will very near the end of her life. She left everything to her neighbours, and nothing to her son.
https://www.lawweb.in/2013/09/capacity-to-make-willmedical-evidence.html