In order to make a Will, you have to possess the necessary legal capacity. No one can make a Will for you or change your existing Will (or other testamentary dispositions) once you lose capacity – not even your attorney for property. The lawyer helping plan and prepare your Will is professionally responsible for determining whether you have the necessary capacity. As a result, the initial meeting to obtain instructions, which is part of the process to determine capacity, must be conducted in private without the involvment of family or others who might try to help by answering for you. A Will can be challenged as invalid if the testator is found not to have had capacity at the relevant time or the testator made the Will under the improper influence of another. A Will can also be challenged as invalid in whole or part if it is found not to reflect the true intentions of the testator. Therefore, lawyers cannot delegate the taking of Will instructions to anyone else. They owe a duty of care not only to the testator but all beneficiaries of the estate.
The legal test for capacity may vary between jurisdictions but generally requires the testator to have a thorough knoweldge of their finances including their obligations to creditors and dependants. The testator must also be able to provide clear instructions regarding the distribution and management of their estate through a Will or other form of testamentary document.
You also need to have reached the required age to make a Will. The age varies across the different jurisictions in Canada but is generally the age of majority in the relevant jurisdiction (meaning the age at which a person ceases to be a minor).