Hey, folks!
I just found something. It may answer why none of Patsy's touch DNA was found on the leggings:
http://connectionnewspapers.com/article.asp?article=318702&paper=80&cat=104
This is it:
"In those rare cases in which blood or other fluids of a suspect are not evident at the scene of a crime, the lab makes use of several of the more niche technologies available, such as Touch DNA or YSTR, to form the profile they need. YSTR analysis works the same way as standard STR,
only it isolates the DNA with Y chromosomes. Since only males have Y chromosomes, the technique becomes useful in certain cases, such as sexual assault, in which a struggle may leave traces of a suspect's DNA underneath the fingernails of the victim. Touch DNA, used in cases where no fluids are available to analyze, use traces of skin cells that may be left at a crime scene."
And since the DA already formed the opinion that it was a male intruder, that's what they'd look for.
As this passage confirms:
"Ian Rodway, chief deputy attorney for the Commonwealth of Virginia, said DNA evidence could be very useful when given the right context.
'That's not to say it doesn't have its limits. Finding traces of a person's DNA or fingerprints on the rearview mirror of a car, for instance,
doesn't automatically implicate a person in that crime.'"
Isn't that interesting? Like I keep saying: it's the DA's imagination that gives this "evidence" it's power.