I must say having read through the posts that I agree with Dave in that a failed identification is seldom recorded. One classic failure to detect the scent of death however was in the Adrian Prout case where the dogs were brought in but failed to identify the burial site even when taken to the very spot. The dogs weren't infallible by any means but merely a means to an end.
Martin Grime couldn't state that Eddie alerted to cadaver scent at the McCann's hire car, to Kate's clothing, the shelf in the bedroom wardrobe or to cuddlecat because as he stated himself on many occasions, the dog alerts are 'meaningless' without forensic corroboration. Since that corroboration did not materialise in the Madeleine investigation we are left with dog alerts which are for all intents and purposes, meaningless.
The dogs did not fail to find Kate Prouts body. They would never have found her body no matter how many times they were taken there. Why is that? It's because she was wrapped in carpet and then wrapped in plastic sheeting..... which is an impermeable membrane.
"Detective inspector Steve Bean of Gloucestershire Police told the inquest that Prout confessed to wrapping the body in a carpet and plastic sheeting and putting it in his Range Rover."
http://www.worcesternews.co.uk/news/9687871.print/ How do you think test materials are transported for testing cadaver dogs? In non permeable containers or they would be alerting all over the place whilst in transit.
Dogs are trained not to scent impermeable membranes. When providing training samples for dogs such odours have to be contained, in gas impermeable containers. This has presented problems in that trainee dogs might begin to identify the scent of container (neoprene, plastic type etc) so they are now deconditioned to alert to such.
By the same token an EVRD which responds to human trace odours only will not identify odour of impermeable membrane around a body So, with right 'wrapping' or containment, dogs can miss cadaver as not trained to scent impermeable membrane.
Eddie alerted in the living room at the Prout house and he was proven correct when Prout eventually confessed to murdering his wife.
Given the dogs training regarding not scenting to impermeables and that Eddie alerted in the living room to where Kate's body had lain, I do not consider that to be a fail by Eddie by any stretch of the imagination.