Michael Montgomery, 21, of Lodi, was arrested Sept. 25, 2013 on suspicion of fatally stabbing Jonathan Denver, 24, near Third and Harrison streets in San Francisco following a game between the Dodgers and the San Francisco Giants at nearby AT&T Park.
He was released several days later, however, after Gascon said he needed more information from investigators before making a decision about filing charges.
On Friday Gascon said his office could not file charges because prosecutors could not prove beyond a reasonable doubt that Montgomery did not act in self defense.
Gascon said prosecutors have interviewed witnesses including members of both groups and independent bystanders, and reviewed evidence including videos and forensics. They determined that, while it is not clear how the argument started, the stabbing occurred during a confrontation between Denver, his brother and Montgomery.
Denver punched Montgomery and his brother hit Montgomery in the head with a collapsible aluminum chair, Gascon said.
"Both the victim and his brother substantially outweighed Mr. Montgomery by 50 and 100 pounds respectively," Gascon said in a statement. "Under these circumstances, Mr. Montgomery inflicted a single stab wound that tragically proved fatal."
Given that multiple sources confirm this account, Gascon said his office could not prove Montgomery was not acting in self defense, and was ethically obligated to drop the case.
Denver, a Fort Bragg plumber's apprentice who was wearing Dodgers clothing at the time of the stabbing and whose father was a security guard for the team, had been watching the game with his father, brother and two others the night of his death. He had left in the eighth inning to go to a bar.
Police Chief Greg Suhr said at the time of Montgomery's arrest that the confrontation that led to the stabbing appeared to have been related to the rivalry between the two teams.