Could someone tell me if the ENTIRE costume was found in Flat Rock or just a portion?
If just a portion...you go with Occam's Razor...the simplest explanation is usually the right one...
Chelsea leaves the party with some guy (MAYBE 2), the drive around, stop at the Flat Rock location and a sexual encounter takes place. We assume that since the costume (or part of costume) was found that she was not agreeable, she may have passed out, she may have wanted to stop and perp took it to rape. I do not think Flat Rock was a purposeful dump site to hide evidence. I think they STOPPED there to rape her or to have an encounter that went bad. They get back into car...perhaps she is still passed out....the perp starts to head back to general area of where she lives...Chelsea either "woke up" or took an opportunity to jump out of car and RAN...perp parks and bails out of car after her...she could be screaming, he catches up to her and she is saying he raped her etc....he panics, and hits her with rock and kills her...runs back to his car and is gone.
The fact that with skeletal remains they say it is homicide before they even get to the coroners tells us she was shot/stabbed and there are obvious holes or knick marks on bones, or she suffered a massive head injury and they can obviously see her skull is fractured. I don't think there was intent to murder, I think he raped her, possibly while she was unconscious, and things started to fall apart from there. It seems rather sloppy to me, like there is not alot of thought...you have 2 crime scenes..where costume was found and where body was found...WHY would he take her back (or at least in the direction of back) to drive a car/truck thru the woods, along the RR tracks, take her out of car and murder her and leave her there? If anything...wouldn't you head further North...away from all the searches and within miles of party? Why would you leave part or all of a costume in Flat Rock? I think because there was no thought of murder and the murder took place in a hurry and spontaneously. JMO