N.Y. Penal Law § 263.25

§ 263.25 Proof of age of child.\n Whenever it becomes necessary for the purposes of this article to\ndetermine whether a child who participated in a sexual performance was\nunder an age specified in this article, the court or jury may make such\ndetermination by any of the following: personal inspection of the child;\ninspection of a photograph or motion picture which constituted the\nsexual performance; oral testimony by a witness to the sexual\nperformance as to the age of the child based upon the child's\nappearance; expert medical testimony based upon the appearance of the\nchild in the sexual performance; and any other method authorized by any\napplicable provision of law or by the rules of evidence at common law.\n