T made three wills, X was beneficiary in 1st and 3rd will. Children of T challenged validity of 1st and 3rd will on the grounds of testamentary capacity and undue influence. Children who had the onus of proof provided medical expert with evidence who claimed T's mental state had deteriorated to such a state that she would not be able to conclude valid will and could be susceptible to undue influence. Court held that will's are invalid due to the T's mental incapacity.