The attorney for a white ex-Bay Area Rapid Transit officer who shot a black man in the back on an Oakland train platform told jurors Thursday that the victim resisted arrest and used racial slurs against police, but the prosecution countered that "aggression took over for training'' and the defendant should be convicted of murder.

The case against Johannes Mehserle was moved to Los Angeles because of extensive publicity in Northern California about the 2009 New Year's Day shooting of Oscar Grant.

The Los Angeles Superior Court jury of eight women and four men -- none of whom are black -- was impaneled Tuesday. Seven jurors are white, four Hispanic and one East Indian.

Alameda County Deputy District Attorney David R. Stein alleges that Mehserle, now 28, murdered the 22-year-old Hayward man during a disturbance at the Fruitvale Station.

The defense contends the officer was reaching for his Taser and mistakenly pulled out his gun.

Grant "was actively resisting'' Mehserle "until the shot was fired,'' defense attorney Michael L. Rains said in his opening statement, telling jurors that video evidence shows Grant "actively wrestled'' with the officer for 12 seconds before the shooting took place.

Using video footage taken by passengers that night, Stein outlined an atmosphere of escalating violence before the shooting.

The case illustrates "what happens when an officer or a group of officers believe their duty'' gives them "the right to abuse or mistrust people -- and they do so in a public setting,'' the prosecutor said.

Mehserle, who had been a BART officer for nearly two years, was so provoked by Grant that he "chose to reach for his holster and pull out his gun,'' and "holding his gun with both hands, he fired a fatal shot into the'' victim's back.

A disturbance had been reported on a train, and the shooting occurred as BART officers tried to control a trainload of revelers on a platform.

Images of the shooting, recorded on multiple cameras, were repeatedly broadcast in the Bay Area.

Rains argued that close scrutiny of the video footage reveals Mehserle making a tragic mistake by pulling what he thought was a Taser out of his holster and pulling the trigger.

The officer had twice "announced his intent to tase'' Grant, before attempting to draw the stun gun four times, not realizing that he was instead trying to pull out his gun, his attorney said.

"Finally, the gun comes out,'' Rains told the jury.

The attorney said Mehserle is seen reacting to the shot, looking down while "the weight of his mistake has just crashed down on him.''

The officer then "brings his hands to his head'' in shock because "he has just shot a man that he did not intend to shoot,'' Rains said.

Stein has argued that the shooting was intentional, the result of Mehserle thinking Grant was reaching for a gun.

The prosecutor said audio from one of the videotapes captures Mehserle telling his partner after the shot was fired, "Tony, I thought he was going for a gun.''

Grant's death "was the result of aggression taking over for training,'' Stein said, telling the panel that Mehserle "should be held accountable.''

Grant died at a hospital of internal bleeding that caused most of his major organs to shut down, Rains said.

At the outset of jury selection, Superior Court Judge Robert J. Perry told panelists the case had been moved to Los Angeles because "there was a great deal of publicity'' in the Bay Area, and that his sole interest was "to have a fair trial for both sides.''

The judge noted that jurors were escorted into the courtroom through a back door and will remain in the courthouse each day during the trial and be served lunch in an effort to keep them from being subjected to outside influences.

Before opening statements began Thursday amid extremely tight security, Perry warned observers that "any attempt to communicate in any way with this jury will be dealt with most severely.''

Mehserle was wearing a bulletproof vest beneath his suit Thursday.

Outside the courthouse, protesters picketed and handed out fliers saying "Justice for Oscar Grant; Shot by Police While Lying Face-Down.''