While activists may place Mr. Chamberlain’s death in the context of police misconduct nationwide, the city’s Department of Public Safety has aggressively defended itself against the $21 million wrongful death lawsuit and charges that it acted inappropriately.

The police commissioner, David E. Chong, declined to comment on the case, citing the pending litigation. But in legal motions filed in recent weeks, the city’s lawyers have portrayed Mr. Chamberlain as a threat in the seconds before he was shot by Officer Anthony Carelli.

“The evidence will show that at the moment Officer Carelli fired, Mr. Chamberlain was on his feet,” charging toward another officer, “with a knife in his hand,” read a motion filed by the city’s lawyers in early October. The motion concluded that “Officer Carelli used deadly force only as a last resort.”

The family, however, contends that Mr. Chamberlain was on the ground when he was shot, based on the location of a bullet hole in the wall, as well as the force of the beanbag ammunition used to subdue him, and the entry point of the bullet wound.

Image Mr. Chamberlain was 68 when he was shot. The officers who responded to his apartment in 2011 were aware that the department had made previous calls to his address. Credit... WABC-TV

Mr. Chamberlain’s son, Kenneth Jr., calls his father’s death a “murder,” arguing that the police should never have forced their way into the apartment in the first place.

Mr. Chamberlain can be heard on the audiotape, made available by the medical-alert agency that recorded the encounter, telling the officers that he was all right and asking them to leave. The agency also tried to cancel its request for a police call. But the officers insisted on checking on Mr. Chamberlain in person.