In Trimarco v. Klein, the New York Court of Appeals held in 1982 that proof of a well-established industry safety custom is admissible and probative evidence of negligence, but never conclusive on its own. A plaintiff who shows that a customary safety practice existed and that the defendant departed from it has built a strong case, yet the jury still must decide whether the custom itself is reasonable and whether ignoring it breached the defendant’s duty of care.
What Happened in the Bathroom
In July 1976, Vincent Trimarco was a tenant in a Bronx multiple dwelling owned by Irving Klein. His bathtub was enclosed by a sliding door made of ordinary, non-tempered glass. Trimarco slipped while stepping out of the shower, fell against the door, and the panel shattered into jagged shards that caused severe lacerations.
At trial, Trimarco showed that beginning in the 1950s, building owners, contractors, and suppliers had widely shifted to shatterproof glazing for tub and shower enclosures, particularly when replacing older glass. By 1976, tempered glass, laminated glass, wired glass, and rigid plastic were all common alternatives. The glass in Trimarco’s bathroom had never been replaced since the building was constructed, and Klein had done nothing to upgrade it despite the long-standing industry shift.
The Rule the Court Announced
The heart of the opinion is the court’s two-sided framework for how industry custom fits into negligence law. When a customary way of doing things safely has developed in response to a known danger, proof that a defendant ignored that custom is strong evidence of negligence. Proof that a defendant followed it can be evidence of due care. Either way, custom is never automatically dispositive. The jury must be independently satisfied that the custom is reasonable before treating conformity or departure as decisive.
Customs, the court noted, “run the gamut of merit like everything else.” The court also quoted Justice Holmes: what is usually done may be evidence of what ought to be done, but what ought to be done is fixed by a standard of reasonable prudence, whether it is usually complied with or not. Following the crowd does not guarantee you met your duty, and departing from it does not guarantee you fell short. Both questions belong to the jury.
Applied to the facts, Trimarco had made out a prima facie case. He proved a widespread practice of using safety glazing for tub enclosures, proved Klein had done nothing to bring the fixture in line with that practice, and proved the ordinary glass caused his injury. That was enough to reach a jury, and the jury’s verdict in his favor deserved respect.
How Custom Evidence Differs From Negligence Per Se
The framework becomes clearer when set against negligence per se. When a defendant violates a safety statute and the plaintiff is within the class the statute protects, many courts treat the violation as automatic negligence. The breach of duty is established as a matter of law, leaving only causation and damages.
Custom evidence carries no such automatic weight. Even with a well-established practice and a clear departure, the jury still evaluates whether the custom was reasonable and whether the defendant’s departure was blameworthy. The defendant remains free to argue that the custom was unnecessary or that the circumstances justified a different choice. A plaintiff relying on custom carries a heavier burden than a plaintiff relying on a statute that squarely applies.
Why the Case Was Sent Back for a New Trial
Trimarco had also introduced New York General Business Law sections 389-m and 389-o, which took effect on July 1, 1973. Section 389-o makes it unlawful to install anything other than safety glazing in hazardous locations, including tub and shower enclosures. Section 389-m defines the qualifying materials. The trial court admitted the statutes and told the jury to consider them “along with all the other proof in this case, as a standard by which you may measure the conduct of the defendants.”
The Court of Appeals held that admitting the statutes was reversible error. The law applied only to installations after its effective date, and Trimarco was not in the class of tenants the statute protected because the glass in his bathroom predated the statute and had never been replaced. Klein’s objection should have been sustained, and the court could not say the statutory evidence had not prejudiced the defense.
That error is why the original verdict was not simply reinstated. The Appellate Division had gone further and dismissed the complaint entirely, reasoning that Klein owed no duty to replace the glass absent prior notice of danger. The Court of Appeals rejected that reasoning, held Trimarco’s common-law negligence case was properly before the jury, but reversed and sent the case back for a new trial free of the improperly admitted statutes.
How Trimarco Pairs With The T.J. Hooper
Torts casebooks usually teach Trimarco alongside The T.J. Hooper, Judge Learned Hand’s 1932 opinion holding that a tugboat company could be found negligent for not carrying radios even though most tugs of the day did not. The two cases approach custom from opposite sides. The T.J. Hooper establishes that following industry practice does not guarantee reasonable care; Trimarco establishes that departing from industry practice does not automatically prove the opposite. In both, the factfinder retains the last word on what a reasonably prudent person would have done, and custom is evidence in that inquiry rather than the answer to it.
Why the Case Still Matters
Beyond the classroom, Trimarco continues to shape premises liability litigation. It confirms that a landlord’s awareness of a widespread safety practice, together with what that practice reflects about a known hazard and a feasible fix, can support a finding of constructive notice of a dangerous condition. A plaintiff does not necessarily need proof that the landlord received a prior complaint or that a similar accident had happened before.
The decision also protects the jury’s role. When a plaintiff comes forward with competent evidence of an established custom and a departure from it, an appellate court cannot take the negligence question away by dismissing the complaint. The reasonableness of the custom, the reasonableness of the defendant’s conduct, and the connection between the two are jury questions, and Trimarco keeps them there.