N.Y. Crim. Proc. Law § 730.70
When a defendant is in the custody of the commissioner on the expiration date of a final or temporary order of observation or an order of commitment, or on the expiration date of the last order of retention, or on the date an order dismissing an indictment is served upon the commissioner, the superintendent of the institution in which the defendant is confined may retain him for care and treatment for a period of thirty days from such date. If the superintendent determines that the defendant is so mentally ill or mentally defective as to require continued care and treatment in an institution, he may, before the expiration of such thirty day period, apply for an order of certification in the manner prescribed in section 31.33 of the mental hygiene law.
N.Y. Crim. Proc. Law § 730.70