N.Y. CPLR 4519
Upon the trial of an action or the hearing upon the merits of a special proceeding, a party or a person interested in the event, or a person from, through or under whom such a party or interested person derives his interest or title by assignment or otherwise, shall not be examined as a witness in his own behalf or interest, or in behalf of the party succeeding to his title or interest against the executor, administrator or survivor of a deceased person or the committee of a person with a mental illness, or a person deriving his title or interest from, through or under a deceased person or person with a mental illness, by assignment or otherwise, concerning a personal transaction or communication between the witness and the deceased person or person with a mental illness, except where the executor, administrator, survivor, committee or person so deriving title or interest is examined in his own behalf, or the testimony of the person with a mental illness or deceased person is given in evidence, concerning the same transaction or communication. A person shall not be deemed interested for the purposes of this section by reason of being a stockholder or officer of any banking corporation which is a party to the action or proceeding, or interested in the event thereof. No party or person interested in the event, who is otherwise competent to testify, shall be disqualified from testifying by the possible imposition of costs against him or the award of costs to him. A party or person interested in the event or a person from, through or under whom such a party or interested person derives his interest or title by assignment or otherwise, shall not be qualified for the purposes of this section, to testify in his own behalf or interest, or in behalf of the party succeeding to his title or interest, to personal transactions or communications with the donee of a power of appointment in an action or proceeding for the probate of a will, which exercises or attempts to exercise a power of appointment granted by the will of a donor of such power, or in an action or proceeding involving the construction of the will of the donee after its admission to probate.
Nothing contained in this section, however, shall render a person incompetent to testify as to the facts of an accident or the results therefrom where the proceeding, hearing, defense or cause of action involves a claim of negligence or contributory negligence in an action wherein one or more parties is the representative of a deceased or incompetent person based upon, or by reason of, the operation or ownership of a motor vehicle being operated upon the highways of the state, or the operation or ownership of aircraft being operated in the air space over the state, or the operation or ownership of a vessel on any of the lakes, rivers, streams, canals or other waters of this state, but this provision shall not be construed as permitting testimony as to conversations with the deceased.
N.Y. CPLR 4519