§ 4519.Personal transaction or communication between witness and decedent or person with a mental illness.

CPLR 4519 keeps a party or anyone interested in how a case comes out, including someone who derives title or interest from that party by assignment, off the stand when it comes to describing a personal transaction or communication with a person who has since died or been found mentally ill. The bar runs against the executor, administrator, survivor, or committee of that deceased or mentally ill person, and against anyone who derives title or interest through them. The concern behind the rule is direct: the person on the other side of the conversation cannot get up and give a competing account, so the statute keeps the survivor from testifying to a conversation the estate has no way to rebut.

That silence is not permanent. If the executor, administrator, survivor, or committee testifies on their own behalf about the same transaction, or if the deceased or mentally ill person's own testimony on the subject is already in evidence, the door opens and the interested witness can testify too. The statute also clarifies what does not count as disqualifying interest: being a stockholder or officer of a banking corporation that is a party does not, by itself, make someone interested for these purposes, and the possibility that costs might be awarded for or against a witness does not disqualify an otherwise competent witness either.

The statute adds a related bar for a different situation: a party or interested person cannot testify about personal transactions or communications with the donee of a power of appointment, in a proceeding to probate a will that exercises that power, or in a case construing the donee's will after probate. That extension closes a gap that would otherwise let interested witnesses describe conversations with a second decedent, the donee, whose account is equally unavailable.

The second paragraph carves out a significant exception for accident cases. Where an action involves a claim of negligence tied to the operation or ownership of a motor vehicle, aircraft, or vessel, and a party is the representative of a deceased or incompetent person, the statute does not make a witness incompetent to testify about the facts of the accident and its results. That exception has its own limit, though: it does not extend to testimony about conversations with the person who died, which remain off-limits under the general rule.