Officer Mary O'Callaghan, an 18-year veteran, was charged by Los Angeles County prosecutors with felony assault under color of authority, lawyer Robert Rico said.
"She's never had a sustained complaint of this type for anything," Rico said. "She has an exemplary record and she's shocked by the decision of the DA's office to file these allegations and looks forward to proving her innocence in court."
O'Callaghan, 48, faces arraignment Tuesday and has been relieved of duty without pay pending an administrative hearing.
The Police Commission, a civilian oversight board, reviewed the July 22, 2012, incident and issued a report concluding that O'Callaghan used unreasonable force on Alesia Thomas, 35, when she was restrained and in the backseat of a cruiser.
The report contained a detailed description of the incident, which was also caught on a police car camera. The department has not released the videotape of the incident and denied a request for a copy from The Associated Press, citing the ongoing investigation.
According to the report, video shows Thomas' "eyes roll back and her body roll toward the driver's seat" before officers reported that she appeared unconscious. Thomas didn't appear to be breathing when she was removed from the back seat. She arrived at the hospital in full cardiac arrest and was pronounced dead by a doctor there.
An autopsy found that Thomas had cocaine in her system when she went into cardiac arrest, but left her cause of death as "undetermined" because the struggle couldn't be excluded as a contributing factor. Thomas, who had a history of bipolar disorder, had no internal injuries or bruising, according to the coroner's report.
O'Callaghan was one of several officers involved in the incident, but the only one whose actions were found to violate department policies. None of the officers were identified by name in the commission's report.
Thomas was pronounced dead at a hospital hours after officers tracked her to her South Los Angeles apartment to arrest her on suspicion of child endangerment. Police said she'd abandoned her 3-year-old and 12-year-old children at a police station at 2 a.m. because she was a drug addict and couldn't care for them. Officers at the station learned the children expected their grandmother to pick them up.
The visit to Thomas' home quickly escalated into a prolonged struggle as officers tried to take the 228-pound Thomas into custody while she had cocaine in her system and appeared "fidgety, wide eyed, sweating" and later "incoherent," even asking officers to let her go and telling them on several occasions to kill her, the commission report states.
When O'Callaghan arrived on the scene, the officers were trying to place Thomas in the backseat of the patrol car. O'Callaghan allegedly repeatedly used profanity while trying to get Thomas into the car and secure her in the backseat while Thomas continued to struggle, kicking her legs toward the window and at O'Callaghan.
Thomas complained of being unable to breathe at one point, but the reports states the officers said they didn't hear her.
The commission specifically noted O'Callaghan's "apparent indifference" to Thomas, but wasn't able to determine whether O'Callaghan deliberately kicked Thomas or was just using her foot to push her into the car. But they determined that the decision to use her foot or leg to move Thomas into the cruiser was "ineffective and inappropriate."
Prosecutors declined to file a charge of involuntary manslaughter, citing insufficient evidence to prove that the conduct caused Thomas' death, according to a press release from the district attorney's office.
The assault charge is punishable by up to three years in state prison, prosecutors said.
Los Angeles Police Union President Tyler Izen said O'Callaghan's actions are "incongruous with her reputation as an officer known to be diligent, courteous and ethical."
O'Callaghan, a southeast patrol officer, was publicly commended by the department in 2004 for her efforts to help a family whose Christmas gifts were stolen in a burglary of their home.
Afterward, the department wrote in a release: "Officer O'Callaghan is commended for her interest in restoring happiness and joy to the (family). This is yet another fine display of the professional attitude displayed by the men and women at the Los Angeles Police Department Southeast Division, placing the interest of the community first."
As for the other officers involved, three have been placed on non-field assignments at other stations and an internal investigation is ongoing regarding potential misconduct. A fourth was allowed to return to the field after it was determined that the officer's role was minor.