ehat test did they use and what are the possible false positives for the "presumptive test"?
I'm WAAAAAAY behind today, but I saw your post about the "blood" on DAW's jacket and motorhome carpet. Since this is something I've been researching a bit, I thought I'd chime in. :o)
The presumptive test uses a little reactive plastic stick sometimes called a Hemostix. It indicates a positive reading for anything with oxygen in it, including blood, saliva, mucus (snot), non-human-provided rust, even insect droppings or squished fly guts. Further testing would be required to determine that the stain is actually blood, and even FURTHER tests to determine if it is indeed human blood--tests which the SDPD did not perform.
In addition, blood can react positively and provide a full DNA profile after 30 years, and a partial profile after more than 50 years. Saliva, even when diluted to 1 part in 100 (like washed or wiped off or dry-cleaned, perhaps), also reacts with a positive reading with the hemostix and provides a full DNA profile even when the stain is more than a dozen years old.
I find it quite odd that a savagely brutal rape and murder provided such tiny remnants of evidence, the same evidence which could have been left in those two locations YEARS earlier (Danielle moved to the Sabre Springs home two years earlier, and that's about how long DAW had that motorhome).
My .02, you understand, but something that certainly seems to indicate a perfectly innocent explanation for Danielle's DNA on DAW's jacket and a tiny spot on the MH carpet. Perhaps a sneeze that sprayed droplets of DNA in a wide radius while she went into the MH to retrieve a wayward Layla, stopping for just a moment to look out the window or regain her balance and leaving a fingerprint on the side of the cabinet.