What is the legal burden of proving that a will has been executed?

Vout v. Hay established that the person propounding the will has the legal burden of proof with respect to due execution, knowledge and approval, and testamentary capacity. Upon proof that the will was duly executed with the requisite formalities, the propounder is aided by a rebuttable presumption, which casts an evidential burden on those challenging the will. That evidential burden can be satisfied by those challenging the will introducing evidence of “suspicious circumstances” – that is, evidence which, if accepted, would tend to negative knowledge and approval or testamentary capacity. If such evidence is adduced, the legal burden reverts to the propounder. By contrast, if undue influence is alleged, the burden is on those attacking the will: pp. 889-890.