New York law has long recognized that evidence of a person’s habit is admissible to prove that the person acted in conformity with that habit on a particular occasion. See Matter of Kellum, 52 NY 517, 519-20 (1873). As stated by the Court of Appeals more recently: “[E]vidence of habit has, since the days of the common law reports, generally been admissible to prove conformity on specified occasions” because “one who has demonstrated a consistent response under given circumstances is more likely to repeat that response when the circumstances arise again.” Halloran v. Virginia Chems., 41 N.Y.2d 386, 391 (1977). Notably, although the New York courts disapprove of evidence of a person’s trait(s) of character offered to prove how a person acted on a given occasion, they are more receptive to evidence of a person’s habit to prove conformity. Barker and Alexander, Evidence in New York State and Federal Courts (2d ed.) §4:41.

Two authoritative sources set forth the basics of New York’s habit evidence. New York Evidence Guide Rule 4.13 defines habit as “a deliberate and repetitive practice by a person … in complete control of the circumstances under which the practice occurs (as opposed to conduct however frequent yet likely to vary from time to time depending on the circumstances.” As to the evidentiary use of habit evidence, PJI 1:71 states “[i]f you find that it was AB’s habit (to act or behave in a particular way), then you may, but are not required to, conclude that AB (acted or behaved) in accordance with that habit at the time in question.”