Undue influence is the most common form of cause of action when instituting a will contest litigation.  In New Jersey, the settled case law emanates from Haynes v. First National State Bank, 87 N.J. 163 (1981) wherein undue influence is defined as “mental, moral or physical” exertion which has destroyed the “free agency of the testator” by preventing the testator from following the dictates of his own mind and will and accepting instead the domination and influence of another.  Yet, the Court stated that it is generally presumed that "the testator was of sound mind and competent when he executed the will."

To establish by presumption that undue influence exists, a contestant must show the existence of a confidential relationship between the testator and the person alleged to have exerted the undue influence and suspicious circumstances as to the will.  In re Will of Landsman, 319 N.J. Super. 252 (App. Div. 1999).

A confidential relationship "includes not only all cases of technical, legal, fiduciary relationship, such as guardian and ward, principal and agent, trustee and cestui que trust, but all cases where trust and confidential actually exist."  Pascale v. Pascale, 113 N.J. 20. A confidential relationship can be held by an attorney, doctor, nurse, business partner, etc.

Suspicious circumstances may exist, for example, where the testator is mentally weak or where the will provisions are unnatural.   In re Estate of Lehner, 70 N.J. 434 (1976).

A contestant may allege that a testator failed to have sufficient mental capacity to execute a valid will.  As to mental capacity to make a will, a testator has sufficient capacity if he understands the general nature of the business in which he is engaged and the particular distribution he is effecting, recollects the property of which he means to dispose and the persons who naturally are the objects of his bounty and comprehends the interrelation of those factors.  In re Blake's Will, 37 N.J. Super. 70 (App. Div. 1955).

Many people are under the mistaken impression that, as a child of the testator, they are automatically entitled to receive under his or her will.  However, in fact, a decedent is not required to convey his estate to his offspring and may pass same to anyone he or she chooses.  A testator of full age and sound mind has the right to dispose of his property by will or deed as he sees fit. Casternovia v. Casternovia, 82 N.J. Super. 251.