As the second day of the first-degree murder trial got underway on Tuesday, Crown counsel filed the admission by Foerster's defence lawyer Lisa Jean Helps that he was responsible for the injuries that killed Van Diest.
The 18-year-old girl from Armstrong, B.C., was found with fatal wounds by the side of railroads tracks on Halloween night in 2011.
Yesterday, the jury heard that the Crown has a taped confession, in which Foerster, now 28, tells an RCMP interrogator that he harmed Van Diest while trying to rape her.
The judge instructed the jury they can now consider this a fact in the case: Matthew Foerster inflicted the injuries that killed Taylor Van Diest.
The judge also instructed the jury that a killing committed during a sexual assault is considered first-degree murder.
Yesterday, Foerster's lawyer entered his plea of "not guilty" to the charge of first-degree murder