The Portuguese Police thought the dogs were 100% accurate.
It is evident that the Portuguese changed tactics following the introduction of the cadaver dogs into the equation. In the following article Kate explains how they were effectively tricked into allowing their possessions and the car hire to be submitted to forensic examination.
Ricardo Paiva (Portuguese Police liaison officer) played a more prominent role in the interrogation this time, giving me his spiel about the dogs. “These dogs have a 100 per cent success rate,” he said.
“Two hundred cases and they’ve never failed.” I just stared at him, unable to hide my contempt. These dogs had never been used in Portugal before, and he knew little more about them than I did.
Could the police have been so naive?

Anguish ... Kate, with Cuddle Cat, and Gerry in tearful appeal for help days after disappearance.
KATE McCann tells today how she wrecked a bed as she kicked out in rage after the first day of the shambolic police hunt for her abducted daughter Madeleine.
http://www.thesun.co.uk/sol/homepage/news/3569557/Kate-McCann-I-smashed-bed-in-rage-at-cops.html
The accuracy of the dogs was sold to the portuguese police by the british, why should they doubt the reports that were presented to them?
The Media had a regal feast bashing the portuguese for not taking the offer of UK dogs for the searches (at the time it was searching dogs that we have plenty and with lots of prizes national and international), later on they diminish the EVRD dogs that were initially announced as top of the world.
Alleging that the recovery of the material was badly conducted is bogus. PT Scientific Police has a very intensive theoretical and practical training in College and on the field - never less than 6 years. In any case if you read the report, if the contamination of the material was true, it points out to have occurred during the lab analysis.
The PT President of the Forensic National Lab was in UK and left quite unimpressed with his colleagues.
Saying the police believed the dogs may be true, because that's what they were told by their british counterparts, but is that a reason to undermine their work?
More telling than the PT PJ using the dogs's indications in their investigation was the complete lack of response from the parents.
How can the father of a missing child respond "Ask the dogs" to a journalist?! How can he be so unconcerned for the possibility that his child could have died? In my opinion, only if he knew what had happened.