It was a grisly scene that combined two deep-seated preoccupations for many New Yorkers: the fear of encountering drunk or deranged people on the subway and the terror of being pushed onto a subway track.

From the moment of his arrest, Naeem Davis, 34, maintained he acted in self-defense just after noon on Dec. 3, 2012, when he shoved Ki-Suck Han, 58, in the chest, sending him onto the tracks at the 49th Street subway station in Manhattan. A few minutes later, Mr. Han, who was too drunk to climb onto the platform, was crushed by a Q train, while bystanders waved frantically at the driver to stop.

The two men had bumped into each other near the turnstiles, and Mr. Davis told the police that Mr. Han had followed him down the platform, berating him with obscenities, grabbing his shoulder and hurling death threats.

The Manhattan district attorney’s office never believed Mr. Davis’s story. Prosecutors brought a murder charge against him, arguing that he had shown a “depraved indifference” to Mr. Han’s life when he pushed him onto the tracks. Mr. Davis was also charged with first- and second-degree manslaughter and criminally negligent homicide.