It's a gratification thing, I think, for the offender, to leave a victim in a degrading pose. It's formulated in their mind, the actual reason(s) for it. I find the dichotomy of how the two victims in this case were left/manipulated to be the most interesting, for numerous reasons. Why was Libby treated so much more severely than Abby? Was it merely because she tried to get away or were there other reasons? Libby was stripped nude, all her protection from the killer removed and never given back fully...just her top half given cover from his eyes with her sexual reproductive parts left bare. Abby was re-clothed, given back her protection and if she was turned upside down...as if the killer couldn't even bear to look at her face after she was covered up, that's significant to me. Did Abby have both her pants and Libby's pants on? Was she given extra protection, two sets of clothing to cover her? Did her killer never even exposed that area of her? It makes me think this was planned somehow to be all about Libby and Abby did not fit his fantasy?
I don't know, just some thoughts and all too disturbing ones. God bless those to sweet little girls and let there be justice for them.