Gurdev Singh Dhillon was convicted of sexual assault for his role in the attack on the woman in Surrey, B.C. His appeal of the conviction was dismissed in 2006.
Neil MacKenzie, spokesman for the criminal justice branch, said officials became aware in 2011 that evidence about the case was not disclosed to the Crown, and therefore not disclosed to the defendant.
"As a result of the ongoing investigation into the identities of additional suspects in relation to the original incident ... during the course of that Crown counsel learned of the existence of material evidence that had not been disclosed at the time of the original trial and subsequent appeal," MacKenzie said.
That information has now been disclosed, MacKenzie said, and it will be up to Dhillon and his counsel to decide whether to seek an appeal with the Supreme Court of Canada.
RCMP said it was their own review of the case that year that raised a red flag and determined that the initial investigation "did not sufficiently consider additional avenues, regarding other potential suspects."
In September 2011, RCMP asked Delta Police to conduct an independent external review and re-investigate the original complaint . The Crown appointed special prosecutor Peter Wilson.
Earlier this month, Wilson approved sexual assault charges against two men: Mohammed Zaaid Ukhttar and Sital Singh Bhatti. The two men are scheduled to appear in court in Surrey on April 5.
The sexual assault was described by the B.C. Appeal Court as "violent and serious."
"It is hard to imagine a set of circumstances more morally repugnant than those in the case at bar," Justice Allan Thackray wrote in the November 2006 decision rejecting Dhillon's appeal.
The judges noted that the "teenager" agreed to go out the evening of July 7, 2004, with two men she'd met at a party two months earlier and with whom she'd spoken several times on the telephone.
The court decision said she was taken to the basement suite of a third man, where she was given alcohol over her objections, and subjected to a prolonged sex assault that included forced vaginal and oral sex, attempted anal sex.
She was punched in the face, threatened with death, choked and impregnated, the judges noted.
Dhillon's defence lawyer submitted to the court that he was "hanging in the background most of the time," the court decision said.
An Indian national being sponsored in Canada by his wife of an arranged marriage, Dhillon was on bail for a spousal assault charge at the time of the rape, it said. He pleaded guilty to assault in September 2004 and was sentenced to one year of probation.
His defence lawyer pointed out to the appeal court that Dhillon could face deportation because of the conviction. MacKenzie said the Crown could not disclose personal information and Canada Border Services Agency was not immediately available to comment on whether a deportation order had been issued.
RCMP Chief Supt. Bill Fordy, the officer in charge of the Surrey detachment, said the mistakes are concern to the force, as well as the public.
"I share those concerns and deeply regret the impacts these mistakes may have had on all those involved," Fordy said in a statement.
"As the officer in charge of the Surrey RCMP, I apologize for the mistakes that were made."
He said when the issue came to light, RCMP took the steps available to correct the situation.
"Two more men have now been charged with sexual assault," Fordy said. "As these matters are now before the courts, we are unable to comment further."
MacKenzie said such instances are rare in the criminal justice system.
"Clearly this was a matter of concern to the branch," he said.
"We take our responsibilities both to the public and to accused persons very seriously, as Crown counsel we take our obligations very seriously, and that's something that continues past the point of prosecution."
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