A teen who pleaded guilty to taking part in brutal sex attacks against a girl and a woman in Winnipeg will be sentenced as an adult, a judge ruled Monday.

The youth, who cannot be named because he was 17 at the time of the 2014 attacks, pleaded guilty earlier this year to two counts of aggravated sexual assault.

A co-accused, Justin Hudson, 22, has pleaded guilty to the same charges.

Justin Hudson, 22, has pleaded guilty to two counts of aggravated sexual assault. (Facebook) During the attacks, a 16-year-old girl was sexually assaulted, struck with a hammer and left for dead along the shores of a frigid Winnipeg river.

The pair went on to beat and sexually assault a 23-year-old woman who suffered a concussion and severe facial injuries.

The teen cannot be named until the sentence is pronounced. Neither the Crown nor defence have made sentencing recommendations yet.

An adult sentence for aggravated sexual assault carries the potential for life in prison. A youth sentence would be a maximum of three years.

Court of Queen's Bench Justice Gerald Chartier said that's not enough time to ensure the youth could be safely reintegrated to ensure public safety.

The youth is considered a high risk to reoffend.

Court has heard the youth has fetal alcohol spectrum disorder, an extremely low IQ and suffers from post-traumatic stress disorder due to abuse he suffered as a child.

He told a psychologist he felt pressured into taking part in the attacks believing Hudson would assault him if he refused. An expert said it was likely his FASD made him vulnerable to peer influence.

The two attackers came upon a 16-year-old girl early on the night of Nov. 7, 2014. They robbed, beat and sexually assaulted her and repeatedly stomped on her head. She ended up in the Assiniboine River but managed to crawl out before being attacked again with a hammer.

She spent a week in hospital and suffered 34 separate bruises and lacerations, Chartier said.

The girl was found by a passerby. She later became an advocate for an inquiry into missing and murdered Indigenous women, however she can't be named under a publication ban.

"I have spent a lot of time in hospitals since you attacked me, repairing injuries to my body," the girl wrote in a victim impact statement read at Hudson's sentencing hearing.

"I have scars on most of my limbs, everyday reminders of that night," she said.

"It's hard for me to find the words to explain the impact that the assault has had on my life. I feel sad. Angry. Confused. It's more than those words can possibly convey. The pain is a heavy weight for me to carry."

Hours after the first attack, the two attackers repeatedly sexually assaulted and severely beat another woman. She spent three days in hospital with a concussion and facial injuries.

"At the time it was happening, I was so scared," the woman wrote in her victim impact statement read at Hudson's sentencing hearing.

"I did my best to 'act' as they wanted me to out of fear that they would hurt me even more. This made me so disgusted with myself and I hated my body for such a long time after."