Deputy District Attorney William Hodgman said there was no evidence photographer Galo Cesar Ramirez deliberately crashed his minivan into Lohan's Mercedes-Benz.
"Based upon the damage sustained to both the victim's and the suspect's cars it appears that, although the suspect was most likely driving carelessly when he collided with the victim's car, it was not an intentional assault," Hodgman said.
Ramirez, 24, was one of several photographers following Lohan from a trendy Los Angeles restaurant on May 31 when the actress made a U-turn and their cars collided. No one was hurt.
Lohan said she was trying to get away from the paparazzi when the May 31 crash occurred.
Hodgman told the Los Angeles Times a wider investigation prompted by the crash was continuing, adding it was possible conspiracy charges could eventually be brought against people responsible for orchestrating risky celebrity pursuits.
The crash was credited with prompting Gov. Arnold Schwarzenegger to sign into law a measure allowing celebrities to collect large damage awards from paparazzi who harass them.