From the legal summary:
"These dogs, which had already been used on multiple occasions by the Scotland Yard and by the FBI with positive results, are evidence collection means and do not serve as evidence; any residue, even if invisible to the naked eye, which is collected using this type of dogs, has to be subject to forensics testing in a credentialed laboratory.
Martin Grime, the dogs' instructor himself [20], mentions in his report: "Whereas there may be no retrievable evidence for court purposes this may well assist intelligence gathering in Major Crime investigations"; or scientist Dr John Lowe [21] who refers that the FSS has no scientific support about the use of the dogs as a fundament for the collection of biological residues and that normally take the handler's word for certification, that asserts that the dogs are more sensitive than any chemical technique or other techniques that are normally used by crime scene sector experts.
In that sense, forensic examinations were performed in the areas and on the objects that were marked and signalled by the blood dog, especially in a credentialed British lab (Forensic Science Service - cf. Appendixes I and VII - FSS Final Report), and also, some of them, at the National Institute for Legal Medicine (cf. Appendix I), whose final results failed to corroborate the canine markings, that is to say that cellular material was collected, which was nevertheless not identified as belonging to a specific person, and it was not even possible to establish said material's quality (namely if it could be blood or another type of bodily fluid)."
What I notice they don't admit that a speck of blood even if it was confirmed to be from Madeleine would NOT indicate that any crime has been committed.