What is the test for establishing a testamentary capacity?

In Kay v. Kay Sr., 2019 ONSC 3166, testamentary capacity was found to have been established after taking into account the totality of the evidence including retrospective neuropsychological evidence and the evidence of the lawyer who took instructions, prepared and saw to the execution of the will of the testator. In that case, the court found the neuropsychological evidence was of modest weight but not inherently reliable since the assessment was not an exhaustive review of the testator’s life in and around the time of signing. Analysis History of the testator’s relationships