A federal appeals court in San Francisco is mulling a bid by former BART officer Johannes Mehserle and two other officers to be shielded from some of the claims in lawsuits by the father and five friends of Oscar Grant III.

Grant, 22, of Hayward, was fatally shot by Mehserle at BART's Fruitvale station in Oakland early on New Year's Day in 2009. Mehserle and other officers were responding to reports of a fight on a BART train.

Mehserle, 30, was convicted of involuntary manslaughter in the state court system in a 2010 trial that was moved to Los Angeles County Superior Court because of intense publicity in the Bay Area.

He testified he intended to use a taser stun gun but accidentally drew his revolver instead. Mehserle was sentenced to two years in prison and released last year after receiving credits that reduced his time served to about a year.

Both the shooting of Grant, which was recorded on cellphone videos by bystanders, and the verdict were followed by large-scale protests in Oakland.

Monday's hearing before the 9th U.S. Circuit Court of Appeals concerned a separate set of federal civil lawsuits filed against several officers by Grant's relatives and five companions who were handcuffed and detained by BART police for several hours.

Parts of the lawsuits have been settled. Sophina Mesa, the mother of Grant's now 8-year-old daughter, Tatiania, settled with BART and officers on behalf of her child for $1.5 million in 2010.

Grant's mother, Wanda Johnson, settled for $1.3 million in 2011.

Remaining in the case are Grant's father, Oscar Grant Jr., who claims loss of familial association, and the five friends, who claim the officers used excessive force and assaulted them when they were detained.

On Monday, a three-judge panel heard arguments for about an hour on contentions by Mehserle, former officer Anthony Pirone and officer Marysol Domenici that they should be protected from parts of the lawsuits by the doctrine of qualified immunity.

The doctrine shields officials from being sued for actions taken in the course of their work that do not violate clearly established rights. The three officers are appealing a 2011 ruling in which U.S. District Judge Marilyn Patel denied immunity on some of the lawsuit claims.

Appeals court judges Mary Murguia, Michael Hawkins and Wallace Tashima took the case under submission and will rule at a later date.

Although other claims in the lawsuits -- including allegations that the officers assaulted Grant's friends -- are not in the pretrial appeal, the panel's eventual ruling on immunity will affect the contours of a future trial or settlement.

John Burris, representing Oscar Grant Jr., argued that Mehserle should not be granted immunity for shooting the younger Grant as he lay on the station platform because the act, Burris contended, was intentional.

"It is clearly a purposeful act if you shoot someone in a helpless position with a firearm," said Burris, who also argued that Mehserle didn't say publicly until months later that the shooting was an accident.

Michael Rains, a lawyer for Mehserle, argued that the allegedly accidental nature of the shooting was shown when Mehserle stood up after firing one round, said an expletive and "I shot him" and then was recorded on a cellphone video putting his hand on his head.

That gesture showed "a man in shock and despair over an accidental shooting," Rains said.

Donald Ramsey, representing Pirone, the first officer on the scene, maintained that Pirone had a reasonable suspicion of Grant and his companions, based on reports of African-American men in dark clothing fighting on a train, when he detained them.

But Dan Siegel, a lawyer for the plaintiffs, argued that Pirone's actions toward the young men were based on racial stereotyping.

"Officer Pirone had no idea whether any of my clients were engaged in a fight and if they were, whether they were victims of aggressors," Siegel told the court.

"He assumed that because they were black males, or dark-skinned males, that they were the aggressors, and immediately took aggressive action," Siegel alleged.

Grant's companions, who were handcuffed and detained at the BART station and then BART police headquarters in Oakland for several hours, were Jack Bryson Jr., Nigel Bryson, Michael Greer, Carlos Reyes and Fernando Anicete.

Two other BART officers, John Woffinden and Emery Knudtson, are also defendants in the lawsuits, but did not participate in the appeal.

In her 2011 decision, Patel ruled that BART as an institution was not legally responsible for the incidents and should be dismissed as a defendant.

Because Patel has retired, the lawsuits have been reassigned to U.S. District Judge Edward Chen, of San Francisco, who will preside over the trial, if one is held.