Pasty said in her statement that Burke wouldn't of got pineapple out to eat because he had a "sweet tooth" and would want chocolate. Maybe JonBenet was protecting the box that she kept her candy in by smearing it with poop. Or Burke did it to get back at her.
I remember in PMPT that Burke had all of Pasty's attention until JonBenet stated school, then Pasty turned her full attention on her. And there is Pasty again overdoing it at school.
BR was said to wet the bed and his pants until Patsy DID turn her attention to his sister.