Light transference of cadaver odour???? After that length of time? What are the McCann's supposed to have wrapped Madeleine in? Where was she kept? It's nonsense.
After three weeks the body would be in stage four -
https://www.futurelearn.com/info/courses/forensic-archaeology-and-anthropology/0/steps/67858
Lace, you've not been paying attention. She was supposed to have been kept in a fridge belonging to one of the group's mystery friends who lived in PdL and who didn't mind helping out or having their petit pois nestling up against a child's corpse for a few weeks. Then, when the coast was clear the McCs went to this Mystery Friend's house and asked for the body back, which they then allowed to thaw out on a trip to Huelva (under the curious gaze of film crew and accompanying media). Somehow the McCs managed to smuggle said rapidly defrosting corpse out of the car and into its final resting place all without anyone noticing, but unfortunately by this point the car was full of defrosted bodily fluids and smelt rank so they had to drive home with the windows open and made a big show of airing the car by leaving its boot open when they got home, for all to see. And that my friend is why the dog alerted (though not to the boot where the body and fluids were sloshing about but to the key fob and the door). Hope that all makes sense now.
Note to Mods: this is satirical and not libel, as clearly I don't believe this happened and have written it tongue in cheek to show how farcical this whole theory is, hope that's OK.