EXPERTS say sniffer dogs can play a vital role in fighting crime ' but warn it is 'madness' to rely on their findings.

The animals are used to lead police to evidence, but do not provide evidence themselves.

One expert told The Sun: 'The dogs can identify traces of blood, but it's crazy to draw major conclusions just from what they find.

'Any evidence they find should be used as a starting point. It's madness just to rely on the findings of the sniffer dogs.'

Handler Martin Grimes, who worked with his dogs on the Maddie case, admitted the animals offered no more than 'a guide'.

He said: 'They can identify traces of blood and detect the smell of a decomposing body, but that is as far as they go.'

Martin said his dogs Keela and Eddie would only give him an indication when they find what they are trained to detect.

Unreliable

He said: 'Blood could be invisible to the naked eye, but Keela will detect it. It doesn't matter if it's hundreds of years old.

'Eddie smells for the scent of a decomposing human body. He can detect any part of a human body that is decomposing ' hair, bones, flesh, anything.

'The smell of a decomposing body is very difficult to get rid of. It can easily be transferred to clothing and on to a person.'

A spokesman for the McCanns said: 'Dog alerts can be unreliable. The handler himself makes it clear in the police report that such alerts are meaningless without corroborative evidence. There was no such evidence.

'Gerry and Kate are not interested in dwelling on mistakes that were made. They and their investigation team wish to focus entirely on finding Maddie.'