The criminal trial of two Los Angeles police motorcycle cops accused of lying under oath about conducting a DUI traffic stop began this week.

Craig Allen, who was fired, and Phillip Walters, who is on suspension from the force, were charged last year with perjury and falsifying a police report.

The incident occurred in Highland Park just after midnight three years ago. LAPD traffic cops were on watch for impaired driving. A DUI task force was in full force that night.

Officer Cecilio Flores watched a driver roll through one stop sign and then another before pulling her over. He said she had bloodshot eyes and smelled of alcohol. Flores radioed over officers Walter and Allen to assist him with the stop and then take over, a “hand-off” as described in court or a "gimme."

The DUI stop continued its fairly routine course. The driver was given a field sobriety test, arrested and transported to jail, and Allen began the paperwork.

That last step, the written police report, is the meat of this case.

“He wrote that he was in the area when they observed and pulled over the vehicle,” said prosecutor Rosa Alarcon in her opening statement. “He didn’t mention Flores.”

Alarcon said Walters later testified during a Department of Motor Vehicles hearing regarding the woman’s driver’s license that he saw her driving that night. She added that officer Allen testified at another hearing giving specific details about how they pulled over the driver -- but admitted that he hadn't personally observed the offense after audio of the dispatch recording was played.

“The defendants made a conscious decision to lie,” Alarcon said.

She didn’t offer a reason why they would commit perjury. Allen’s defense attorney Bill Seki took aim at that.

“There was no motive,” Seki said. “There was nothing to gain.”

In his opening statement, Seki said Allen simply made a mistake on the written report and relied on that report six months later when he was called to testify about the arrest.

Attorney Joel Isaacson, who represents Walters, built on that during his opening statement.

Isaacson said Walters filled out a small portion of the police report and never saw the completed paperwork before he was sent home because his partner was going to finish writing it.

“If there is no reason to lie, it’s a mistake,” Isaacson said. “An honest, human mistake.”

The dryness and simplicity of this perjury case is what makes it unusual. Two cops said they observed the impaired driving and made the traffic stop, when facts show they didn’t. One side calls it lying; the other calls it an error.

When the two officers turned themselves in after criminal perjury charges were filed against them, LAPD Chief Charlie Beck released a statement saying the department holds officers to the highest standards of integrity and professionalism.

“I do not believe that their intent was evil, just extremely misguided,” Beck said in the statement. “The character of our organization is defined by the conduct that we condone. These actions were entirely unacceptable."

Beck issued a very similar statement four months later when two other LAPD officers were found guilty of perjury in a 2008 drug possession trial.