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Colin Winsor was sentenced to serve 18 years in jail for killing Ashton Moen, 17, seen here in an undated family photo. ((Handout))

An Alberta man must serve at least 18 years in prison for killing a teenage girl and dumping her body on the side of a rural road, a judge decided Friday.

The judge said 32-year-old Colin Winsor must serve at least 18 years of his life sentence before he is eligible for parole.

Winsor was convicted in March of second-degree murder and indecent interference with human remains in the 2006 death of 17-year-old Ashton Moen.

The conviction carried an automatic life sentence with no parole for at least 10 years.

Moen's body, wrapped in a blanket and tied with a cable, was found on July 1, 2006, beside an irrigation canal just outside the southern town of Brooks, about 160 kilometres southeast of Calgary. The Grade 11 student had gone missing more than a week earlier.

During his trial, Winsor told the court that he struck the teen in the head in self-defence. He said Moen came at him with a knife after he said he didn't want a relationship with her.