N.J. Stat. § 2A:81-2: Transactions with mentally incapacitated person; decedent; proof required.

In a civil action that is commenced or defended by a guardian on behalf of a person who is mentally incapacitated or by a personal representative on behalf of a decedent, any other party who asserts a claim or an affirmative defense against the person who is mentally incapacitated or against the personal representative, that is supported by oral testimony of a promise, statement, or act of the person who is mentally incapacitated before the onset of mental incapacity, or of the decedent, shall be required to establish the same by clear and convincing proof.

amended 1960, c.52, s.45; 2013, c.103, s.15.