The 'unmitigated evil' of kidnapping and repeatedly raping a teenage girl has netted two Calgary brothers 12-year prison sentences.

"[It's] certainly one of the most depraved offences that I've ever been involved with," said prosecutor Jonathan Hak.

"Just unmitigated evil, frankly."

Provincial court Judge Terry Semenuk sentenced the brothers Friday morning after the pair pleaded guilty in 2016 to kidnapping and sexual assault.

In November 2014, the 17-year-old victim was waiting for a bus in Taradale after watching a movie with a friend. The brothers dragged her into an alley, where they physically and sexually assaulted her.

Afterward, they forced the girl to walk with them to their home in Martindale, where they continued to rape her throughout the night. The girl was able to escape in the morning while they were sleeping.

The sentencing hearing had been delayed several times as experts examined the pair, who both suffer from severe impairments like "extreme" fetal alcohol spectrum disorder (FASD).

With credit for the time they've already served, Cody has seven years and 10 months left to serve while Corey has seven years and three months.

Crown worries about 'repeat performance'

Hak and co-counsel Zailin Lakhoo had argued for 12-year sentences and asked Semenuk to order the pair to serve at least half of their sentences before they can apply for parole. Semenuk made that order.

"The court clearly appreciated the seriousness of the offence and the dangerousness of these offenders," Hak said outside of court.

"We need to keep them in jail as long as possible because of community safety. For both of these fellows, what became so clear in this prosecution is that there is very little that society can do to prevent a repeat performance."

The judge agreed with prosecutors Jonathan Hak and Zailin Lakhoo and imposed 12 year sentences for the Manyshots brothers. (Meghan Grant/CBC)

Much of the judge's written decision reviews both offenders' impairments, which leave them at a moderate to high risk of violently reoffending once they are released from prison.

Corey has an IQ of 45, suffers from schizophrenia and functions at the level of a six-year-old child. His lawyer, Mitch Stephensen, had proposed a 6½-year sentence followed by three years of probation.

Stephensen also recommended his client attend a residential treatment program for people with mental illness and substance abuse in Ponoka, following his release from prison.

Victim 'getting on with her life'

Cody's lawyer, Alain Hepner, was seeking a nine-year prison sentence for his client. He says his client's parents, both of whom were in court for Friday's sentencing decision, were "upset."

Given the brothers' severe FASD and other issues, Hepner has previously said the two didn't stand a chance. He reiterated that sentiment on Friday.

"They come from a disenfranchised background," said Hepner.

"The FASD report put them at the high end of fetal alcohol syndrome, their life was such that they never really had proper schooling. Like I said to the judge, they fell between the cracks of life."

The victim was not in court but the prosecutors have kept her up to date and say she's "doing quite well."

"I think it's a very difficult thing to ever get over and I don't think we really expect her to get over it," said Hak.

"But she is getting on with her life."