Three members of a Yale University chorus were back in San Francisco on Monday to testify against two local men accused of attacking them during a New Year's Eve party, an altercation a defense lawyer characterized as a fight between two groups of rowdy guys.

William Bailey, a member of the a cappella singing group the Baker's Dozen, said tempers flared at the party early on New Year's 2007 after the visiting Yale singers sang "The Star-Spangled Banner" and a member of their troupe kissed a San Francisco woman at the same party.

Bailey said he tried to calm one of the angry local men, who followed the singers outside and then punched him in the face.

"I was very stunned that he hit me," Bailey said. "He said we were cool, but clearly that wasn't the case."

Richard Aicardi and Brian Dwyer, both 20, have been charged with felony assault and battery in connection with the brawl. Bailey and the other Baker's Dozen members testified at the pair's preliminary hearing on Monday.

Under cross-examination from Aicardi's defense lawyer, Jim Collins, Bailey and his troupe mate, Evan Gogel, said they had been drinking before the clash. Outside court, Collins said the case was not a one-sided strike against innocent victims.

"The Yale boys were not little angels," Collins said. "They were argumentative, uncooperative with police and intoxicated."

Gogel testified that after leaving the party he was attacked by four or five men who kicked him repeatedly, and that he had seen fellow singer Sharyar Aziz Jr. being assaulted. Aziz suffered a broken jaw, but prosecutors did not charge anyone with his assault because they did not have enough evidence.

Aziz has sued Dwyer, Aicardi, two of Aicardi's brothers and another man.