Nineteen-month-old Suzie Pena was being used as a human shield by her father, District Attorney Steve Cooley said in a memo made public Tuesday.
Relying on a review of the scene and reports gathered by the police department, prosecutors found the SWAT officers were trying to defend themselves and others when they accidentally killed the child, Cooley said.
The father, Jose Raul Pena, exchanged gunfire with police during the hours-long July 2005 standoff before he was fatally shot. There were illegal drugs in his system and traces of cocaine in the toddler's system, officials said.
The girl's death raised questions about police tactics and led to an internal LAPD investigation and separate FBI and district attorney's office probes.
District attorney investigators concluded SWAT team officers had reason to shoot at Pena after he opened fire on them. One officer was struck by a bullet fired by Pena.
"The officers ... entered the office where Pena held Suzie hostage, and in fear for their lives and the lives of others, the officers fired several rounds at Pena," the memo said.
The Los Angeles Police Commission was to determine later Tuesday whether any of the officers violated department policy.
Investigators in the 15-month internal probe were unable to determine which officer fired the shot that killed the girl, Chief William Bratton said Monday.
"That's unfortunate, but that's pretty much where we are with it," Bratton told the Los Angeles Times.
An attorney representing the child's mother has filed a claim against the city as a precursor to a lawsuit.