@Skully I just watched too. The DNA. I always thought is a red herring. I thought the undies were new ones pulled out of a new pack and too big for her. Not washed so the DNA could be from manufacturing, shipping, the store they were bought...etc. And also was touch DNA, so small bits of skin cells.
The DNA under her nails....could that be from other kids or people at the party that night? Or should it even be her own DNA if she had been digging into her neck to loosen the garrot?
The Suitcase under the window mentioned above...great points. Dirt wouldn't have still been on his shoes nor would the glass likely be there. And I remember something about them saying the broken glass was old and covered in debris. Not newly broken. Even John mentions breaking that window to get in previously. So then, is he saying the bad guy slipped in an already broken window? Convenient.
It does all come down to that ransom note. Written on PR note pad. Written way too long and dramatic like a book (like the book on her bedside table). Amount asked is not a normal number and is similar to his bonus.
Also kid kidnappers/killers don't hang out in a house for all that time doing their deeds, they take kid and go. They don't do a long torturous murder/SA, rifle through office to see info on bonus amount, write a dramatic play like several page ransom note (after doing practice notes), carry body to basement and then rifle through storage room to get Suitcase and climb out window
...not to mention making the garot. Like what? Someone of the 3 there did something (thinking the head injury was the start) and a cover up was staged.