HBO is set to premiere the documentary "Beware the Slenderman" today.

It could impact the cases of the two teens charged.

Annisa Weier and Morgan Geyser, both 12-years-old at the time of the crime, have not gone to trial yet.

They are accused of stabbing a classmate several times in an effort to please the fictional character "Slenderman".

A defense attorney we spoke with says the documentary could impact the trial from jury selection, to testimony even sentencing.

Both girls entered pleas of not guilty by reason of mental disease or defect.