Their test for blood was negative, as was Stefanoni's test. They did not have a chance to test the bra clasp, because it was incomprehensibly stored in the presence of extraction buffer, causing it to rot and rust. They made the correct decision not to amplify the DNA sample that they did find IMO. That noted, the fact that Amanda's DNA was later identified actually strengthens the case that Meredith's profile arose from a source that is unrelated to the crime. How can one clean a bloody knife so thoroughly that it escapes the limit of detection (at least one part in 500,000) yet leave DNA in two places and starch in at least one? It is absurd.