When someone creates a will, it is assumed that it is valid and should be legally binding, as it is supposed to contain the wishes of the decedent. This is why legal challenges to the validity of the will, known as a will contest, are often thrown out of the court unless they meet stringent legal requirements.
First of all, a will contest must be filed by someone who had standing. This means they have a financial interest in the estate. Either the person challenging the validity of the will is named as a beneficiary in the will or would have legally inherited from the decedent had there been no will. Creditors can also contest a will if they were owed money and the will as it stands would prevent them from collecting that money.
After demonstrating standing, the second point that must be demonstrated in probate litigation are the grounds upon which the will was contested. For example, a challenger would have to prove that the decedent lacked mental capacity, was unduly influenced, was defrauded, or a procedural mistake was made. An example of a procedural mistake would be that the correct number of people had not witnessed the execution of the will.
Wills can be contested before going into probate through filing a caveat that puts the public at notice that the will should not be admitted into probate or after probate opens but usually within 90 days of it. To understand when and how a will can be contested and how to prevent one from happening, it might be beneficial to consult an experienced attorney on how to proceed.