A 19-year-old man charged with participating in the beating and gang rape of a 16-year-old girl at Richmond High School outside of a homecoming dance in October 2009 pleaded guilty in Contra Costa County Superior Court Friday.

Ari Abdallah Morales of San Pablo is expected to receive a 27-year prison sentence after pleading guilty in a Martinez courtroom this morning to rape in concert, penetration with a foreign object and forced oral copulation in concert, Senior Deputy District Attorney John Cope said. His sentencing is set for Jan. 13.

According to police, Morales and a co-defendant, Marcelles Peter of Pinole, both penetrated the victim with foreign objects and stood by as she was beaten and raped by co-conspirators.

Manuel Ortega, 22, was the first defendant to plead guilty to charges in the gang rape case. He accepted a plea deal in September and was sentenced to 32 years in prison last month on charges of rape in concert, rape with a foreign object in concert and forced oral copulation in concert while inflicting great bodily injury and robbery.

Police said witnesses saw Ortega punch and kick the victim after she refused to give him oral sex and stepped on her head while a co-defendant, Jose Carlos Montano, 21, raped her.

Montano is scheduled to appear in court in Martinez on Nov. 30. The four remaining defendants in the case are set to return to court for status conferences on Dec. 13.