District Attorney George Gascon says prosecutors do not have enough evidence to prove that 21-year-old Michael Montgomery of Lodi did not act in self-defense when he killed 24-year-old Jonathan Denver.
The incident occurred on Sept. 25, 2013 during an argument following a baseball game at AT&T Park in San Francisco.
The victim had attended the game with his brother, father and two others to celebrate his father's 49th birthday. The group, many wearing Dodger garb, left the park after the 8th inning for a nearby bar.
At some point, they got into a shouting match over the Dodgers with Montgomery and a few friends who were bar-hopping in the trendy South of Market area. At least one was wearing a Giants cap.
Montgomery's father said his son was acting in self-defense after his group of friends was "jumped" by the group of Dodger fans, and that he stabbed Denver after Denver struck his son in the head with a chair. Denver's brother disputed that claim.
"While it is not clear how the fatal encounter started, what the evidence shows was a physical confrontation between the victim, the victim's brother and Mr. Montgomery," Gascon said. "The totality of the evidence revealed that during the physical confrontation, Mr. Denver punched Mr. Montgomery."
Denver and his brother outweighed Mr. Montgomery by 50 and 100 pounds, respectively, Gascon added. Witnesses have corroborated this version of events.
"With multiple sources indicating how the event transpired, it makes it impossible for us to meet our burden and prove beyond a reasonable doubt that Mr. Montgomery was not acting in self-defense," Gascon said. "We are ethically obligated to decline to prosecute this case."
The Associated Press contributed to this report.
