Do you know that it would be unusual to detect footprints on a tile floor in a place where no crime had occurred? I honestly don't know, but the results from Raffaele's apartment suggest it might not be unusual.
Keep in mind that not only did the police do a TMB test that came back negative on every one of the bare footprints, they also did DNA tests, and Meredith's DNA did not show up in any of them. You are taking the position that the defense must explain how the footprints were made in order to establish a reasonable doubt. That is absurd. The forensic test results, in and of themselves, go far beyond establishing a reasonable doubt. They constitute strong evidence that the footprints were not made with Meredith's blood. Factor in the random locations of the prints and the lack of evidence that anyone with bare feet stepped in blood inside Meredith's room, and the net result is a practical certainty that these footprints have nothing whatsoever to do with the crime. They are random artifacts.
We are talking about footrints matching Amanda's feet on ascene where a crime occurred and where there are isolated bare footprints in diluted blood.
These footprints form a system showing non-random features.
Footprints all around the house, footprints forming a trail wpuld be a random artifact. It is not likely that only part of the trail is cleaned as thye wash the floor, because usually, in a normal routine, people clean the hole floor, not pieces of floor here and there. If part of the trail was cleaned in an operation of cleaning only part of the floor, you would see footprints cleaned by half, pieces of footprint left and remains.
The artifact in question doesn't have this random features, by which we could try to link it to "old" remains of normal operations. You cannot assert that you can expect to randomly find isolated footprints of a right-foot reacting to lumiol, and overlook any need of explanation for it.
Moreover the finding shows multiple footprints in Amanda's room, and no other similar "random artifact" in other rooms in the house.
About the TMB test, the fact is all literature says it shall not be used as confirmatory test, nor posively neither negatively. The TMB test used in this case is indirect, it requires the collection of a liquid sample from the stain, and this operation is itself an information filter. You know that Mederith's DNA did show in some of the luminol artifacts, and was also mixed with Amanda's. Some are in places where they should not be, like Filomena's room. How would you expect to find Amanda's and Meredith's DNA mixed on spot that reacts to luminol in someone else's room? How many odds do you think you have? We also know that Meredith's DNA did not show up in some traces that were visible and were blood for sure. And we know that DNA test may be not that sensitive and subject to deterioration when exposed for long to bacteria and agents (we are talking about samples collected several weeks later). This is expecially true if DNA is from white cell nucleus (very fragile) instead of epithelial cells. We also know that there were blood traces that showed
only Amanda's DNA, primarily the blood drop on the faucet. This is highly significant, even if it is not Meredith's DNA. Bear in mind that I'm looking for evidence of Amanda's
presence on the scene of murder, not specifically for Meredith's DNA.