What does 'testamentary capacity' mean and how does it affect my will?

Testamentary capacity is the legal standard that determines whether a person is mentally capable of making a valid will. In Ontario, courts have historically assessed it using a four-part test: the testator must (1) understand the nature and effect of making a will, (2) understand the general nature and extent of their property, (3) know who their natural heirs are (sometimes called the "natural objects of their bounty"), and (4) be capable of holding all of this information together to form an orderly plan of distribution.

Capacity is assessed at the moment the will is signed, not before or after. A person can have a condition like early dementia and still have testamentary capacity on a good day. Conversely, someone who appears healthy may lack capacity due to medication, intoxication, or other factors at the time of signing.

If capacity is later questioned, courts look at medical records, witness observations, and lawyer notes from the signing. This is why having a lawyer draft and witness your will is valuable — they can note their observations about your understanding and demeanor, creating a contemporaneous record that is hard to dispute.