Chance Wilson is accused of injecting a lethal dose of meth into his 16-year-old sister, Saleda Wilson.
She was found dead inside a northeast Oklahoma City home in July 2012.
One mother later her brother was charged with her murder.
Court records show Chance admitted to giving Saleda back-to-back shots of meth.
Her father later found her dead.
Saleda and Chance’s mother said the past 15 months have been unbearable.
Chance’s trial is scheduled to start at 9 a.m.