Alameda County prosecutors are opposing bail for Johannes Mehserle, arguing that the former BART police officer convicted of involuntary manslaughter for fatally shooting an unarmed passenger has no realistic chance of winning his appeal.

Mehserle's lawyers are scheduled to ask a Los Angeles judge Friday to release him while he appeals his conviction and two-year prison sentence. They argue that he would pose no danger while on bail and has legitimate grounds for overturning the July 8 guilty verdict, such as jury instructions that the defense says confused the members of the panel that convicted Mehserle.

Mehserle, 28, shot Oscar Grant in the back while the 22-year-old Hayward man lay face-down on the platform at Oakland's Fruitvale BART Station on Jan. 1, 2009.

In convicting Mehserle of involuntary manslaughter rather than murder, the Superior Court jury accepted a defense argument that the officer, responding to chaotic conditions on the platform after a fight on the train, thought he was using his Taser shock weapon instead of his pistol.

The jury also found that Mehserle had personally used a gun, a verdict that normally would add three to 10 years to his sentence. But Judge Robert Perry dismissed the finding, saying no reasonable jury could have concluded that Mehserle had intentionally used the gun, a legal requirement for the sentence increase.

District Attorney Nancy O'Malley's office could appeal that ruling, but gave no indication of whether it would do so in papers filed with Perry opposing bail for Mehserle.

A convicted felon is eligible for bail only if defense lawyers show a substantial likelihood of a successful appeal, and they failed to do so in this case, prosecutors said.

Mehserle's lawyers argued that the evidence showed he acted innocently, rather than recklessly or with gross negligence, when he drew and fired his gun, so there was no legal basis for the involuntary manslaughter conviction.

But prosecutors said both the jury and Perry had rejected that argument. Because the judge had properly told jurors they must find criminal negligence to convict Mehserle of involuntary manslaughter, any confusion from other jury instructions was minor and inconsequential, prosecutors said.

"The defense arguments have little prospect of success on appeal," prosecution lawyers told Perry.