No criminal charges will be filed against a former California Highway Patrol officer who punched a bipolar woman as she walked on a busy Los Angeles freeway, prosecutors said Thursday.

The Los Angeles County District Attorney's Office said in a statement that Officer Daniel Andrew acted within the law by resorting to force to stop Marlene Pinnock from entering traffic.

Pinnock was recorded on video being repeatedly punched while resisting arrest.

She could not be reached for comment and it was unclear whether she had a lawyer. Her previous attorney, Caree Harper, was sanctioned in March for refusing to say how she met Pinnock and when she learned her client might be mentally incompetent. Harper could not be immediately reached for comment Thursday.

Andrew resigned following the July 2014 incident, and the CHP paid $1.5 million to settle a lawsuit.

"There is insufficient evidence to prove beyond a reasonable doubt that the force he used was unreasonable or excessive," a 30-page report on the probe into the incident says.

District Attorney Jackie Lacey says the video did not show what led up to the struggle.

"When looking at all of the evidence, and especially the medical reports and eyewitness accounts, it becomes exceedingly clear that the officer, who was alone and struggling with Ms. Pinnock precariously close to evening freeway traffic, acted within the law," Lacey said in a statement.

"In our analysis, his use of force was legal and necessary to protect not only his own life but also that of Ms. Pinnock," she added.

Pinnock suffered no lasting injuries from the struggle, the district attorney's office said, citing medical records.

An independent use of force expert hired by the District Attorney's office found that "the absence of injury to Ms. Pinnock's head and face ... indicates that if any of the strikes hit her head, they were glancing, ineffective blows," according to the report.

In October, highway patrol officers took Pinnock into custody after she was spotted walking on the same stretch of road. Pinnock ran into traffic when officers tried to detain her, according to the CHP. She was removed from the road and taken to a hospital for a mental health evaluation, the Los Angeles Times reported at the time.