Defense For Ex-LAPD Officer Accused of Assault in In-Custody Death Gets Ready to Present Case in Trial

After five days of prosecution witnesses, the defense for a former Los Angeles Police Department officer is getting to present evidence in the case.

Mary O'Callaghan is charged with assault under the color of authority stemming from the 2012 arrest of Alesia Thomas and now stands trial for assault in Thomas' in-custody death.

The defense's first witness Thursday was a retired LAPD officer who now makes a living as a use of force expert.

Ron McCarthy spent the morning testifying about the various levels of force and when and why each one should be used.

The defense attorney went over the use of verbal commands in detail with the prosecution hammering away at the fact O'Callaghan used profanity and foul language with Thomas as she tried to get her into a patrol car.

McCarthy said while he was offended by some of the language and wouldn't use it himself, he explained why it's used instead of using physical force.

"Some are expected to create minor injury, so in order to avoid that and we can elevate our language, tactical language, that's fine," he said.

O'Callaghan lost her job with the LAPD after the department investigated the arrest of Thomas, who lost consciousness in the backseat of the patrol car and later died. O'Callaghan was then charged with a felony.

The last moments of Thomas' life were captured by a camera mounted inside an LAPD patrol car. They are moments which have been played over and over in court.