02/13/2012 06:24 EST | Updated 04/14/2012 05:12 EDT

Man Pleads Guilty To Murder Of Stepdaughter, 17

The stepfather of a 17-year-old Calgary girl killed two years ago pleaded guilty to first-degree murder on Monday, saying he strangled the teen while raping her.

The guilty plea came as the two-week trial of Bradley Wade Rietze, 47, was about to start.

Brittney Nora McInnes’s body was found in a box spring in her Canyon Meadows home in January 2010.

Her mother had reported the 17-year-old missing.

When police searched the home, they did not find the Grade 12 student.

It was hours later that a family member searched the house and found her body stuffed into a box spring.

Rietze — McInnes's stepfather for 13 years — was charged with the girl's slaying a few days after her body was found.

Rietze pleaded guilty against the advice of his lawyers.

First-degree murder in Canada carries with it an automatic sentence of life with no possibility of parole for 25 years.

The sentencing hearing will be held on Wednesday at 2 p.m. MT, when victim impact statements will be read.