What a fascinating link.
It is quite informative and at 2011 more recent than most. It is actually a fascinating subject which I find very interesting but the consensus is that it is not an exact science; although the skills of the dogs are never in question just our interpretation of them maybe.
Anecdotal evidence about a dog's nose:
I placed an unopened pack of dog chocolate treats on top of a large bookcase;when my labrador came through the doorway she immediately whirled, sat down with nose in the air pointing at the treats which she could not see but certainly could smell because I had never put anything edible in that place before.
They can be trained to sniff out specifics such as bed bug infestations which have become a big problem in America ... I don't think there is much their noses can't tell them ... but in criminal cases their indications must be backed up with evidence and that is right and proper.