P was injured when he fell through the glass door enclosing his tub in his apartment he was renting. P was severely injured. It was not possible for P or his wife to determine if the glass was tempered or just ordinary glass. After the accident, the glass was found to be just ordinary glass. P sued Klein (D), his landlord, for the injuries. At trial, P introduced expert evidence about the custom and usage of tempered glass from 1956 to 1976. Since at least the early 1950s, a practice of using shatterproof glazing materials for bathroom enclosures had come into common use, so that by 1976 the glass door here no longer conformed to accepted safety standards. P also showed that over this period bulletins of nationally recognized safety and consumer organizations along with official Federal publications had joined in warning of the dangers that lurked when plain glass was utilized in 'hazardous locations,' including 'bathtub enclosures.' Over objection, the trial court also allowed in sections of New York's General Business Law, which, as of July 1, 1973, required, on pain of criminal sanctions, that only 'safety glazing material' be used in all bathroom enclosures. D's managing agent admitted that, since at least 1965, it was customary for landlords who had occasion to install glass for shower enclosures, to replace the glass with 'some material such as plastic or safety glass.' P was given the verdict by the jury. The appellate division reversed the decision awarding P damages; D was under no common law duty to replace the glass unless he had prior notice of the danger. P appealed.