A Napa man charged with killing a 26-year-old man during an argument on a Marin County beach more than a year ago has been acquitted.

On Friday, a Marin County jury acquitted Robert Martell, 25, of Napa of involuntary manslaughter in the May 27, 2007, death of Casey Adams, 26, of Santa Rosa.

In addition to Martell, two other men, Daren Corbett Bell, 25, of Napa, and Robert Allen Marcus, 22, of Elk Grove, were arrested in connection with Adams’ death.

Bell pleaded guilty to felony battery and was sentenced to one year in county jail, Marin County District Attorney Ed Berberian said Tuesday afternoon.

Marcus pleaded guilty to the same charge and is scheduled to be sentenced within the next two weeks, Berberian said. “He has the potential to face a prison term.”

Berberian said the victim and his friends, who were camping at Dillon Beach, got into an argument with Martell, Bell and Marcus in the early morning hours of the day Adams died.

Martell is a reservist in the U.S. Marines who recently returned from a tour of duty in Iraq, according to the Santa Rosa Press-Democrat.

During his trial, Martell said he was acting out of self defense, Berberian said. “The jury found reasonable doubt to find Mr. Martell not guilty of involuntary manslaughter.”

Berberian said Bell admitted he hit Adams in the back of the head with a flashlight. “However, at the trial a doctor testified those blows did not cause his (Adams) death. The cause of death were blows to his face.”

Berberian said the incident lasted only about four seconds.

Berberian said the prosecution’s investigation showed Marcus and Martell inflicted the death blows to Adams. Berberian also said Adams was intoxicated and had methamphetamine in his system.

Correction: An earlier version of this story misstated information about the case and misspelled the name of Daren Bell.