If the making of the Will is caused by implementing fraud or coercion or undue influence then that Will is Void.

Fraud can be caused by misrepresentation or concealment of facts to the Testator.

Coercion is committing or threatening to commit on Testator any act which is forbidden by law.

Undue Influence is caused when a person is in position to dominate the testator to make the Will as that person wants.