If a life insurance policy is contested stating dementia will a basic assessment from a neurologist stating normal mental capacity hold up in court?

It sounds as if both sides will have some medical evidence to support the claim, but it also seems like both medical notes mentioned are from a few months before the change took place.  For that reason, it is unlikely that the issue will be fully determined by only one medical record or the other.  The respective sides may be able to bring in other evidence (e.g., testimony from friends and family) that will shed additional light on your grandmother's mental status in December 2010, and ultimately a determination will need to be made as to whether she was competent at the time that she made the change.  Other factors could include the relationship she had with the original beneficiary (and the changed-to beneficiary).  These types of disputes can be complicated, so I would not recommend going it alone.  You should speak with an attorney in your area with some experience in these types of disputes and issues.  Hopefully you can get a free consultation, and then you will be in a position to make a more informed decision.  Good luck going forward.  -Jay Mills