A Last Will and Testament of a deceased person can be challenged in a proceeding to impeach the Will. Grounds for impeaching a will include lack of testamentary capacity by the testator (the person signing the will), forgery (the deceased person did not sign the Will) and undue influence (the will provisions resulted from pressure from another person and do not reflect the decedent's intent).
A person who signs a will must have testamentary capacity. The law defines such capacity as "knowing the natural objects of your bounty" (who your family is), knowing that you have an estate (what you own generally), and that the document you are signing, the will, says what happens to your estate after you die. The testator can be sick or have impaired intellect at the time they sign their will and still have testamentary capacity. The capacity needs only to exist at the time the Will is signed.
There is a presumption that if a Will is properly executed, that is, it has the right number of witnesses and a self-proving affidavit, if required, that the testator had testamentary capacity. The burden is on the person challenging the Will to prove that that the testator did not have testamentary capacity.
A presumption of undue influence arises where the testator was "enfeebled in mind" when the will was executed, a confidential or fiduciary relationship was accompanied by activity in obtaining or preparing the favorable will (for example the person who wrote the will is a beneficiary under the will) and the testator previously had expressed a contrary intention with respect to disposition of his property. The burden of proving undue influence rests on the person saying the will is the result of undue influence.
