N.Y. RPA Law § 401

§ 401. When interests are valued under this article. The following\ninterests shall be valued in the manner provided by this article: (a) an\ninterest in real property dependent as to value upon the duration of one\nor more lives in being, whether such interest is present or future; and\n(b) a future interest preceded only by one or more interests described\nin clause (a); whenever 1. the owner of such interest is entitled to\nreceive a sum in gross in satisfaction of, or in compensation for\nimpairment of, his interest in real property which has been transformed\ninto a fund by judicial action or proceeding; or 2. ownership of real\nproperty is divided into successive legal interests, including one or\nmore interests dependent as to value upon the duration of one or more\nlives of persons in being, and the fraction of complete ownership\nbelonging to each partial owner must be ascertained so as to permit an\nadjudication of the fraction of some new capital expenditure required\neither for the payment of a mortgage, special assessment or other lien\nupon such property, or for the satisfaction of an obligation imposed by\nlaw as an incident of ownership; or 3. such valuation is necessary for\nthe final determination of some action or proceeding, other than an\naction or proceeding for which the insurance law, the workmen's\ncompensation law or the tax law prescribes methods of valuation.\n