OAKLAND -- The Alameda County District Attorney's Office will not appeal a Los Angeles judge's decision to drop a gun enhancement conviction of former BART police Officer Johanes Mehserle that would have added more time to the sentence he is serving for involuntary manslaughter in the Jan. 1, 2009, fatal shooting of Oscar Grant III, officials said.

In a statement issued late Thursday, District Attorney Nancy E. O'Malley said that "after a review of the transcripts recording the action taken by Judge (Robert) Perry and an extensive consultation with the California Attorney General's Office, Criminal Appellate Division, it has been determined that efforts to appeal Judge Perry's ruling would not change the result."

Michael Rains, Mehserle's attorney, said today that he believes the judge "knew what he was doing" when he made the ruling, and that the district attorney's decision not to appeal was "appropriate considering the major uphill battle" they would have faced in successfully appealing.

Attorney John Burris, who represents Grant's family in civil lawsuits, said he still "strongly disagrees with the judge's analysis" but can understand why the district attorney decided not to appeal.

"I'm not surprised," Burris said today. "The family is disappointed but they understand it would have been an uphill battle, and even if it had been granted the same judge would have conducted the retrial."

Burris said he does not think the judge gave "due consideration" to Mehserle's conduct and the fact that he did not tell anyone for some time that he made a mistake when he reached for his gun rather than his Taser.

He said the family still hopes that Mehserle and another BART officer present at the scene, Anthony Pirone -- who has since been fired -- will be prosecuted by the federal government for violating Grant's civil rights. "It's not over yet," he said.

The Los Angeles County jury that convicted Mehserle of involuntary manslaughter on July 8 also convicted him of a gun enhancement clause. That conviction would have added up to 10 years to his term.

But when Perry, a Los Angeles County Superior Court judge, sentenced Mehserle on Nov. 5, he dropped the enhancement, sentencing him to two years in prison. With credit for time served, Mehserle could be out of prison in five or six months.

Mehserle was prosecuted for murder in the death of Grant, 26, of Hayward, who was fatally shot in the back by Mehserle as he lay on the platform at the Fruitvale BART station. During the trial he admitted shooting Grant but testified it was accidental and that he thought he was using his Taser to subdue him. The trial was moved to Los Angeles out of concerns that Mehserle would not get a fair trial in Alameda County because of extensive media coverage.

At the sentencing, Perry said that after a review of the testimony and other evidence, he determined no reasonable juror could have concluded Mehserle's use of the gun was intentional and dismissed the enhancement conviction.

Mehserle is appealing his involuntary-manslaughter conviction. A state appeals court denied his request to be released on bail pending the outcome of the appeal application.