Dogs are used around the world.
Why ?
because they do the job their trained for.
SY used them in Portugal.
So when don't they work ?
the mccanns.....
and gerry boy says they're no good, and you got to believe him, cus he knows everthing. 
The dogs which are used around the world do the job they are trained to do which in the case of cadaver and CSI dogs is to indicate areas of interest from which evidence may be gathered for forensic testing; and which may be later used in court.
This can be anything from a corpse to parts of a corpse or blood splatter even if an attempt has been made to 'clean up'.
The cadaver dog if trained using pig, will react to pig.
It will also react to every substance expelled from a living human body such as spit, fingernails, blood, excrement … as these all begin to decay immediately on separation.
When the dogs worked in Portugal … nothing evidential was found.
They found no trace at all of Madeleine McCann and certainly no proof of her death.
However if you refuse to take Martin Grime’s word for it, you will hardly take mine. But your stance tends to make you look rather ill informed.
"So when don’t they work? The mccanns" … absolutely incorrect, there are very many occasions when unfortunately they don’t "work" otherwise there would be no such thing as a victim’s body lying undisturbed for many years despite intensive searching.
In the case of Suzanne Pilley from Edinburgh ... despite her body not being found yet ... a conviction was enabled helped by the use of a cadaver dog. Not only the VRD indications , but on a trail of evidence in which the dog alert played a part; without further substantial supportive evidence the dog alert on 'cadaver scent' would not have got the suspect to court because it is not evidence of anything on its own.
