There are tests for the capacity to make a Will:

The person making the will (Testator) must understand:

1. The nature and effect of making a Will
2. The extent of his or her estate
3. The claims of those who might expect to benefit from the testator’s will (both those being included in, and being excluded from, the Will)

The Testator cannot have a mental illness which:

1. Influences the testator to make gifts in the Will that he or she would not otherwise have included
2. Capacity can be a temporary understanding at the time of signing a Will or when the Will is drawn up with subsequent knowledge that a Will is being signed.