Section 250.20 - Notice of alibi1. At any time, not more than twenty days after arraignment, the people may serve upon the defendant or his counsel, and file a copy thereof with the court, a demand that if the defendant intends to offer a trial defense that at the time of the commission of the crime charged he was at some place or places other than the scene of the crime, and to call witnesses in support of such defense, he must, within eight days of service of such demand, serve upon the people, and file a copy thereof with the court, a "notice of alibi," reciting (a) the place or places where the defendant claims to have been at the time in question, and (b) the names, the residential addresses, the places of employment and the addresses thereof of every such alibi witness upon whom he intends to rely. For good cause shown, the court may extend the period for service of the notice.2. Within a reasonable time after receipt of the defendant's witness list but not later than ten days before trial, the people must serve upon the defendant or his counsel, and file a copy thereof with the court, a list of the witnesses the people propose to offer in rebuttal to discredit the defendant's alibi at the trial together with the residential addresses, the places of employment and the addresses thereof of any such rebuttal witnesses. A witness who will testify that the defendant was at the scene of the crime is not such an alibi rebuttal witness. For good cause shown, the court may extend the period for service of the list of witnesses by the people.3. If at the trial the defendant calls such an alibi witness without having served the demanded notice of alibi, or if having served such a notice he calls a witness not specified therein, the court may exclude any testimony of such witness relating to the alibi defense. The court may in its discretion receive such testimony, but before doing so, it must, upon application of the people, grant an adjournment not in excess of three days.4. Similarly, if the people fail to serve and file a list of any rebuttal witnesses, the provisions of subdivision three, above, shall reciprocally apply.5. Both the defendant and the people shall be under a continuing duty to promptly disclose the names and addresses of additional witnesses which come to the attention of either party subsequent to filing their witness lists as provided in this section.N.Y. Crim. Proc. Law § 250.20