Jennifer Shen testified that the dirt was from the site where Danielle was found (see first and last excerpts below):
Q: IT APPEARS IN PHOTOGRAPH C ON THE FIBER FOUND ON DANIELLE'S NECKLACE THERE ARE BLACK SPOTS FOR LACK OF A BETTER TERM.
A: YES.
Q: TELL US ABOUT THAT.
A: WELL, THE FIBER THAT WAS REMOVED FROM THE NECKLACE, FIRST OF ALL, IT HAD TO BE UNTANGLED FROM THE HAIR AROUND THE NECKLACE, AND IT WAS COVERED IN DEBRIS AND KIND OF GRIME, DARK DEBRIS, SOME SOIL, AND IT WAS DIRTY. SO WHEN I TOOK THE FIBER OFF, I HAD TO CLEAN IT. AND WHEN I DID THAT, I REMOVED QUITE A BIT OF THE DIRT AND GRIME FROM THE FIBER, BUT THERE IS SOME DIRT AND DEBRIS LEFT ON IT. AND WHAT YOU ARE SEEING IN THAT PICTURE IS SOME OF THE DEBRIS THAT HAS NOT BEEN REMOVED FROM THE FIBER.
Q: SO NOT PART OF THE FIBER ITSELF.
A: CORRECT.
Then she describes the fiber tangled in hair in a large clump:
THE WITNESS: IN THE AREA WHERE THE HAIR IS CONCENTRATED IN A LARGE CLUMP, THAT IS WHERE I FOUND THE ORANGE FIBER. IT WAS TANGLED IN THE HAIR IN THAT AREA.
Finally, she states that the fiber likely came to be there close in time to her death due to the way it was tangled and the debris from the Dehesa site:
Q: MISS SHEN, I'LL ASK THE QUESTION AGAIN. AS FAR AS THE LOCATION OF THAT FIBER IN THE HAIR, TANGLED IN THE NECKLACE, IS THERE ANY SIGNIFICANCE TO ITS LOCATION AS OPPOSED TO IT BEING, FOR EXAMPLE, IN ANOTHER LOCATION ON THE NECKLACE?
A: THE SIGNIFICANCE I THINK OF THE FIBER TANGLED IN THE HAIR IS THAT BECAUSE IT WAS KNOTTED IN THE HAIR AND BECAUSE THE HAIR WAS KNOTTED IN THE NECKLACE AND BECAUSE THE FIBER IS COVERED IN DEBRIS AND THE HAIR AND THE NECKLACE ARE COVERED IN A SIMILAR DEBRIS, IT APPEARS THAT THE FIBER AND THE HAIR WERE ON THE BODY FROM THE TIME THAT IT WAS PLACED WHERE IT WAS FOUND VERSUS HAVING BEEN PLACED ON THE BODY AT SOME LATER TIME.IT ALSO IS REASONABLE I THINK TO CONCLUDE THAT THAT FIBER CAME IN CONTACT WITH THE BODY AND THE NECKLACE AT OR NEAR THE TIME OF HER DEATH.