The dog didn't pick up the profusely bleeding male's chin blood anywhere else- apart from behind the sofa.
We either have to accept that the dogs picked up scent where it was in relation to the exercise OR dismiss them out of hand.
a( If agree the dogs did pick up scent then we should agree that the places where the profusely bleeding man, bled; would be highlighted by the dog.
b) If we disagree, why bother to mention the bleeding man at all, as we don't believe the dog did pick up any scent.
Finding Maddie's blood would have to be further investigated as to why it was there, in the particular place. If she had a nose bleed-would there not be traces in other places? There could be an innocent explanation-or not.
Having a suspicion needs to be moved on to proof of a scenario.
With regards to the cadaver... a dog cannot smell any individual persons death. The dog will highlight a dead person was here, It cannot distinguish if the dead person was male, female, child or adult.