Police in Oakland underwent crowd-control training and were put on 12-hour shifts as they awaited a verdict in the shooting death of an unarmed black man by a white transit police officer who claimed he mistakenly drew his gun instead of his Taser.
Mehserle, 28, has pleaded not guilty to murder in the shooting of 22-year-old Oscar Grant after a fight drew officers to the Fruitvale train station on New Year's Day 2009. Grant was shot while lying face down on the platform.
Several bystanders videotaped the New Year's Day 2009 incident -- perhaps the most racially polarizing trial in California since four Los Angeles police officers were acquitted in 1992 in the Rodney King beating case.
In his closing argument, Alameda County Deputy District Attorney David Stein said police officers are supposed to protect and serve, not abuse their authority.
"We also entrust them with our lives and our fellow citizens," Stein said. "Oscar Grant represents one of those citizens."
Defense attorney Michael Rains contended the shooting was a tragic accident. He cited testimony that his client had inadequate training to prevent weapons confusion and witnesses who said Mehserle appeared to be in shock after shooting Grant.
"On Jan. 1, 2009, Johannes Mehserle fired a single gunshot and it brought him to this place before you, and you are his shot at justice," Rains told jurors, citing a line from the 1982 legal drama "The Verdict," starring Paul Newman.
In Oakland, police braced to prevent a repeat of the rioting that occurred after people first saw the grainy videos of the shooting.
A statement released Friday said the department had taken precautions, including shifting resources and identifying mutual aid options.
"We anticipate protests following the reading of the verdict and have heard of possible outside agitation in an attempt to turn the peaceful movement into acts of civil unrest," the statement said.
In Los Angeles, already tight security around the courthouse will be beefed up on verdict day.
"We have taken all precautions," county sheriff's spokesman Steve Whitmore said. "You will see a large number of deputy sheriffs, significantly more than before, and there will be stuff you won't see."
Mehserle resigned from the Bay Area Rapid Transit agency after the shooting. His trial was moved from Alameda County to Los Angeles because of excessive media coverage and racial tensions.
Another officer was heard on video uttering a slur before the shooting, but no evidence was presented during the trial that Mehserle's actions were influenced by prejudice.
Jurors must decide if Mehserle should be acquitted or found guilty of second-degree murder or a lesser offenses of voluntary or involuntary manslaughter.
The incident sent Oakland into a tailspin as violent street protests intensified the debate on whether Mehserle knowingly shot Grant, a young father from Hayward, Calif., who had been recently released from jail.
He became a martyr of sorts. His omnipresent image on buildings and storefront windows across Oakland arguably rivals that of slain hometown rapper Tupac Shakur.