Mary O'Callaghan, 50, had been convicted in June on a charge of assault under the color of authority
, the Los Angeles County District Attorney's Office said Thursday in a press release.
Los Angeles County Superior Court Judge Sam Ohta sentenced her to the maximum term of 36 months but suspended 20 months of the sentence, the DA's office said.
The conviction came as complaints about police violence -- especially against minorities -- are increasing. O'Callaghan is white. Alesia Thomas, who died the night of the arrest, was black.
CNN affiliate KTLA has earlier reported that prosecutors didn't charge O'Callaghan
with manslaughter or murder because there was insufficient evidence to prove her conduct caused Thomas' death. Thomas' official cause of death was "undetermined," according to a coroner's report.
On July 22, 2012, Thomas dropped off her two children at a police station because she felt her drug abuse had made her an unfit parent, according to Los Angeles County Supervisor Mark Ridley-Thomas.
Police talked with Thomas at her house and arrested her. O'Callaghan arrived on the scene and helped fellow officers put Thomas -- then wearing handcuffs and leg restraints -- in a patrol car, the DA's office said.
"A police cruiser's video camera captured O'Callaghan kicking Thomas in the stomach and groin area and pushing her in the throat," the DA's office said. "While in the patrol car, Thomas lost consciousness and paramedics were called. She was transported to a hospital where she was pronounced dead."
According to the Los Angeles Times, O'Callaghan's attorney
, Robert Rico, said his client used her foot to push Thomas into the patrol car but didn't kick her. He said Thomas had not complied with officers' orders.
"I was very concerned about this incident when it was first brought to light," LAPD Chief Charlie Beck said in a department press release. It was our investigation that ultimately led to the criminal charges against her and now a prison sentence."
"It should be clear to everyone that the LAPD and the criminal justice system will hold officers accountable for their actions when they operate outside the law."
O'Callghan has been relieved of duty without pay, according to the press release.