In November, Judge Robert Perry granted the defense's motion for a new trial regarding a gun enhancement that the jury added to Mehserle's involuntary manslaughter verdict in the Jan. 1, 2009 shooting death of 22-year-old Oscar Grant III at the Fruitvale BART station in Oakland.
In doing so, Perry reversed the finding of the jury and dismissed the gun enhancement, according to the district attorney's office.
After reviewing the transcripts that recorded actions taken by Perry and consulting with the state Attorney General's Office, the district attorney's office concluded that an appeal of Perry's ruling "would not change the result."
Although Alameda County prosecutors sought a second-degree murder charge in Grant's killing, on July 8 the jury convicted Mehserle of the lesser charge of involuntary manslaughter, sparking large, destructive protests across downtown Oakland.
During his trial, Mehserle admitted that he shot and killed Grant but testified that it was an accident because he had meant to fire his Taser stun gun instead.
Jurors also found that Mehserle had personally used a gun, but Perry dismissed that finding when he sentenced him on Nov. 5, saying it was unreasonable to conclude that Mehserle intentionally used his gun.
That enhancement would have added up to 10 years to Mehserle's two-year sentence.
The trial had been moved to Los Angeles because of concerns about whether Mehserle could receive a fair trial in Alameda County after extensive coverage of the shooting received by Bay Area media.
On Dec. 20, Mehserle's defense team filed an application with the California Court of Appeals requesting bail pending appeal, but that request was struck down two days later.
Mehserle will be eligible for parole in about five months, according to his lawyer, Michael Rains.