It is one thing to write a will. It is another to prove that when the will was written the will-maker had the capacity to appreciate the consequences of doing so.
Once a doubt is raised as to the existence of testamentary capacity, an onus rests on the person propounding the Will to satisfy the court that the will-maker had the requisite mental powers. Specifically did the will-maker:
Where a will-maker is not found to have the requisite capacity the will in question will not be able to be probated. However, the prior will can be (presuming capacity at that time). See In the estate of Ruth Annie Howie
Where questions are raised regarding capacity (and more than one will has been made), it is not sufficient to seek probate of and earlier will on the basis that the the will-maker may not have had capacity at the time the later will was made. The correct course of action is to seek probate of both wills in the alternative so that the Court can determine the question of capacity. See In the Estate of Norren Joyce Watson.
Another issue to consider in the context of capacity is the implications of testing and developments in future capacity predictions and what questions laywers might need to be asking of their clients in the future. See Medical tests for capacity.
Probate in Solemn Form
Where capacity of a will-maker is challenged, the application for probate should be in solemn form. See Re Estate of Lorne Anthony Crowley. In that case Gault J found the will-mkaer to have testamentary capacity noting that:
 There is evidence that raises Mr Crowley’s lack of capacity as a tenable issue, namely that he made the will while a patient in the FMU and on the very day that he received ECT treatment, which affected his cognition at least temporarily. That being so, the onus of satisfying the court that Mr Crowley did have testamentary capacity rests on the applicants who seek probate of the 7 August 2018 will.
 There was no medical assessment of Mr Crowley’s testamentary capacity at the time of making the will on 7 August 2018, but I consider that Mr Crowley did have testamentary capacity to make that will, for the following reasons.
 Ms Law gave evidence that when she discussed the terms of the will with Mr Crowley on 7 August 2018, he was adamant that he wished his daughters to be his sole beneficiaries and did not want the prior will to stand. Ms Law said that prior to executing the will, Mr Crowley conveyed a clear understanding of the extent of his property and his wish to leave his property equally to his two adult children. Ms Law said she would not have witnessed Mr Crowley executing his will if she had any doubt about his capacity to do so.
 Although Dr Jones noted when he witnessed the will that he had not examined Mr Crowley’s testamentary capacity, his evidence was that at the time of the will change Mr Crowley had some cognitive impairment but his performance on cognitive testing at the time was consistent with mild cognitive dysfunction, which neither excludes nor supports his having testamentary capacity. Dr Jones acknowledged that Mr Crowley’s depressive symptoms potentially could have influenced his attitude towards the relationship with Ms Shegarenko, and the decision to remove her as the principal beneficiary of his well. At the time of the will change, Mr Crowley’s depression had partially improved, but not remitted. Psychotic beliefs regarding Ms Shegarenko had apparently remitted by the time of the will change. Dr Jones noted that Mr Crowley’s comments and actions at the time, and subsequently, were consistent with the change in beneficiaries specified in his new will. In particular, Dr Jones noted that Mr Crowley’s comments and actions in relation to Ms Shegarenko before and after the will change indicated that he believed their relationship had finished.
 While the change from the prior will was significant, it was relatively straightforward and consistent with the end of Mr Crowley’s relationship with Ms Shegarenko and with Mr Crowley’s moral obligation to his two adult children.
 Finally, if it were necessary because of concern about the residual effect of the ECT treatment on the morning of 7 August 2018, I would have applied the rule in Parker v Felgate on the basis Mr Crowley had testamentary capacity when he gave instructions to Ms Law on 6 August 2018.
Re Estate of Lorne Anthony Crowley highlights the wisdom of a contemporary assessment of capacity, particularly when the circumstances of the will-maker are such that inquiry is virtually inevitable.