what the dogs picked up would very much depend on what sent they were given to track.
These two dogs, Eddie and Keela, are not tracker dogs in that they are not trained to follow the scent of a person. Keela has been trained to detect only human blood even after items have been cleaned or washed many times. The other dog, Eddie, has been trained to detect human remains and cadaver odour. They have been used in hundreds of cases. Obviously, they can't denote who the person was and are just a tool to be used alongside all other evidence.
The interesting thing about them being used in this case is that they alerted to two places in the holiday apartment -both of them behind the sofa, with just Eddie alerting at the wardrobe in the parents' bedroom. He also alerted at the flower bed outside.
Other places they alerted to were an item of Madeleine's clothing, the cuddle cat, Kate's trousers, the luggage area of the hire car and the car keys.
Kate's response was that she had worn the trousers to work the previous week leading up to the holiday, where she was present at six deaths of patients during her work as a part-time GP, and that she had also taken the soft toy to work with her. The smell in the boot of car was put down to 'dirty nappies'.