Q: Can a will be challenged on the ground that my father was so sick that it is impossible for him to sign a will with a conscious mind?
A: You may challenge the will on the ground of lack of testamentary capacity of your father at the time when a will was signed.
Essentially, the testator must understand the nature of the act and effects of signing a will. He must understand the extent of the property he is disposing. He must understand the claims of his property that he will give effect upon his death.
To determine whether a person has a testamentary capacity, the court will look at the soundness of the mind of the testator and NOT the particular state of bodily health.
Q: What is the meaning of soundness of the mind of the testator?
A: To displace testamentary capacity by reason of soundness of mind, proof of serious illness is NOT enough. There must be clear evidence that illness of the testator affects his mental faculties eg. mental disorder or insane delusion. To the extent that he is not able to dispose of his property in a will on the day the will is made. There should be medical evidence that support the testator does not have testamentary capacity.
Courts have in the past made the following observation. Terminal cancer patient (even if he is deaf and dumb), chronic diabetic and patient who had serious accident which left him in a quadriplegic condition – did not mean the deceased did not have the testamentary capacity when making the will.
Q: Who has the legal burden to prove lack of testamentary capacity?
A: The legal burden is on the party who challenge the will to prove that the testator lacked the testamentary capacity to make the will.
ZH 
EN 
MY