It's also a fact that Eddie could not tell Grime how old the scent was, or whether it was from above or below ground, or whether the original source was at the spot where he barked or whether the scent had drifted there from elsewhere. Or even if it had been innocently transferred there from an outside source by cross contamination.
Hence his statement that the alerts are of no use unless they can be corroborated. Without corroboration there are just too many variances which could have nothing to do with Madeleine which could have resulted in an alert.
So ultimately - they add nothing to the investigation.
Quote from Amarals book:
Eddie is always the first to be brought onto a site. Once he has discerned the odour that he knows so well, it’s Keela’s turn to go into action, on the lookout for the slightest whiff of blood. The simultaneous presence of the two elements in a given place - blood and cavaver odours - is taken to indicate that a body has been there and that it’s probably there that the death occurred.
Unquote
Amaral was obviously unaware (or chose to ignore) that Eddie also alerted to blood - which included blood from living people - and so what he claims in his book is patently seriously flawed. I cannot help but wonder how many people who read it - believed what he claimed and judged the McCanns guilty as a result.