This is my first post so hopefully it will work.
The DNA from the undies was tested by touch DNA methods and matched the DNA on her long johns. Therefore the DNA was left on undies & outerwear by same person?
Fact?
Welcome to the forum! Guess your post worked!
FACT? Maybe, maybe not. Here's why:
The DNA was what is known as "touch DNA". Is consists of DNA extracted from skin cells- in other words, skin cells that were transferred by someone who TOUCHED something. The thing with Touch DNA is it may not necessarily been left by the person whose skin cells are found. The DNA found on JB's clothes may have been left by someone who touched the same thing that the donor of the DNA also touched- like a doorknob, etc.
We know that both parents touched JB's clothing around the waistbands. Patsy said she dressed JB in the longjohns that night- and JR was SEEN to be holding the dead body of his daughter upright with his hands around her waist, so we KNOW he touched the waistbands.
Here's the thing- ALL the Rs attended the same party. They may ALL have touched the same doorknobs, toilet handles, sink faucets, etc. Had JB touched something the donor of the DNA also touched, his skin cells would have transferred to her fingers, and then onto her clothing, assuming she put the longjohns on herself or pulled them up or down. The same is true of her parents- if the donor was a party guest, they may also have picked up his skin cells.
That is why the Touch DNA is not something that positively identifies the killer, or even someone who was there at the time she was killed. That DNA may not even have anything to do with the crime. It isn't like DNA from a primary source, like semen, saliva, blood, etc.
So to answer your question, it is not CERTAIN that the same person left the touch DNA, though it is possible. And it is not CERTAIN that the donor of the skin cells was there at the time of the crime or had anything to do with the crime.
This is why is was so damaging to this case (and to justice for JB) that the former DA Mary Lacy said that this DNA exonerated the parents. It did no such thing, and the next DA said as much.
FACT- this DNA exonerates NO ONE, and NO ONE can be excluded as a suspect from this crime, especially the three people who were PROVEN to be in the house at the time JB was killed,
until and unless someone has been identified by NAME and shown to have been in Boulder at the time of the crime.