At this point I wish the investigators would stop calling this a "homicide." I truly do not think anyone intended for JBR to die that night. Therefore, it's a killing as a result of an accident/moment of rage. There can't be any "justice" for JBR because the head bash cannot be taken back--Spitz confirmed that injury was fatal. Her heart continued to beat for some time, but her brain was mortally wounded--she was in essence a goner.
You can't today arrest BR for what he did in 1996 as a 9 yr and 11mo old child. I know people wish they could see the handcuffs and a perp walk, but that isn't going to happen. The Boulder DAs office could have brought charges against JR & PR for the obstruction of justice and endangerment, but they didn't and now it's too late.
But it wasn't really a "murder" in the sense that (IMO) intent was not part of this. Yes, the R's intended to cover it up and stage the scene to throw off investigators. Yes, that is a crime because it's illegal. But *IF* Burke inflicted the head bash, it's not considered murder. He may have intended to hit her, but legally-speaking he couldn't form intent to kill.