Two men were found guilty on all charges Thursday in the gang rape of a teenage girl outside a Richmond High School homecoming dance, a spokeswoman for the Contra Costa County district attorney said.

Jose Montano, 22, of Richmond, and Marcelles Peter, 20, of Pinole, were tried by separate juries on charges of gang rape, oral copulation and sexual penetration with a foreign object.

They each also faced a special allegation that the acts committed during the October 2009 assault inflicted great bodily injury on the victim. The men could face 33 years to life in prison when sentenced.

During the incident, which made national headlines, numerous assailants raped, beat and robbed the 16-year old girl for more than two hours while at least 20 men and boys watched.

A woman finally called police after her brother-in-law told her that while he was near the campus, some boys told him there was a girl in the darkened courtyard with whom he could have sex.

Much of the evidence was presented before both juries simultaneously in the Martinez courtroom of Contra Costa Superior Court Judge Barbara Zuniga. The panels heard closing arguments and deliberated separately.

Montano and Peter were the first to stand trail of the six men jailed in connection with the assault.

The girl -– identified at trial only as Jane Doe -- had left the dance early and began drinking with a group of men and boys before they attacked her.

Officers found her slung over a picnic table support beam, mostly nude and suffering from head trauma, burns and hypothermia, Deputy Dist. Atty. John Cope said at trial. Her blood-alcohol level was a near-fatal 0.35.

Peter’s jury returned a verdict Tuesday and Montano’s on Wednesday, but they were not read in the courtroom until Thursday.

Peter’s attorney, Gordon Brown, had maintained that his client was a witness but had not participated in the sexual assault. However, Cope told the jury that Peter’s DNA was found in a discarded condom. Also introduced at trial was a police interrogation video in which Peter said he touched the victim’s private area before Montano raped her.

Two other men, Manuel Ortega, 22, and Ari Morales, 19, are serving 32-year and 27-year prison terms for their roles in the rape after reaching plea deals with prosecutors. Two other defendants are awaiting trial on lesser sexual assault charges. Additional DNA found at the scene has not been matched to suspects.

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lee.romney@latimes.com