New York has long recognized that credibility of any witness can be attacked by showing an inconsistency between the witness's testimony at trial and what the witness has said on prior occasions, once a proper foundation is laid and subject to the sound discretion of the trial judge. See Guide to New York Evidence Rule 6.15, and accompanying note. Courts, attorneys and commentators view the use of prior inconsistent statements as one of the most effective techniques of impeachment. See Barker and Alexander, "Evidence in New York State and Federal Courts" [2d ed] §6:49. As stated by the Court of Appeals in Larkin v. Nassau Electric Railroad: "Repugnant statements or contraries cannot be true; and the fact that the witness has made them tends to show that [the witness] is untrustworthy through carelessness, and uncertain memory, or dishonesty."

The rules governing impeachment by prior inconsistent statements as set forth in Guide Rule 6.15 are well-settled. Yet errors in their application, or a misunderstanding thereof, do occur, as shown by recent Appellate Division decisions. Perhaps a refresher on these rules is worthwhile. A refresher is also timely due to a proposed amendment to Federal Rule of Evidence 613, governing impeachment by prior inconsistent statement, changing present federal practice, which if adopted, will take effect in December 2024. This column will seek to provide such a refresher.