N.Y. Dom. Rel. Law § 144

§ 144. Proof required. 1. In an action to annul a marriage, a final\njudgment annulling the marriage shall not be rendered by default for\nwant of an appearance or pleading, or by consent, or upon a trial of an\nissue, without proof of the facts upon which the allegation of nullity\nis founded. Plaintiff shall prove that there has been no such\ncohabitation between the parties as would bar a judgment except that in\nan action under subdivision (c) of section one hundred forty the\nplaintiff may prove instead that the mental illness still continues.\n 2. In any action, whether or not contested, brought to annul a\nmarriage, the declaration or confession of either party to the marriage\nis not alone sufficient as proof, but other satisfactory evidence of the\nfacts must be produced.\n