Indeed, much of the advice has this subtext: behavior that strikes a police officer as suspicious may have a cultural explanation. For instance, police recruits are told that when entering a Puerto Rican household they are likely to encounter a lot of “eye-checking.” Rather than interpreting these glances among family members as an effort to prevent one another from speaking candidly, officers should understand that the mannerism “relates to the closeness of the family unit.”

The guide reminds officers to consider that immigrants may be especially fearful of the police because in their native countries the police were involved in rampant human rights violations.

“In such places, people learn early that there is little to gain and much to lose by trusting the police or by telling them the truth,” the manual states. “No matter how friendly, trustworthy, and helpful we may try to be, habits and traditions learned during a lifetime of oppression do not die easily.”

“Your interactions with immigrants from countries like Haiti, Cambodia, El Salvador and Guatemala will go more smoothly if you take the time to assure them that you will not hurt them,” the guide also states.

The origins of these communication tips are not entirely clear. The Police Department’s chief spokesman, Paul J. Browne, said only, “The multicultural material was introduced decades ago but is updated periodically to reflect the changing face of the city.” He added that the tips come from a variety of sources, “including community leaders, academics and experienced law enforcement personnel.”

The lessons, Mr. Browne said, are “consistent with the literature and texts utilized by universities.”

Mr. Browne declined to make police instructors available for interviews about the training.

During the stop-and-frisk trial, a police witness, Chief James Shea, testified that the department’s training emphasized to recruits that “there is no cookie-cutter approach to policing in New York City.” The underlying lesson of the manual, said Chief Shea, who once commanded the Police Academy, is to ensure that officers “don’t assume that the person you’re dealing with comes from the same life experience as you and is reacting the same way to what is happening.”