I weep if Amber is really a govt lawyer...
How are we supposed to take seriously a book by a presumably educated lawyer and journalist who has never heard of the Stasi? And who goes on to assume her audience hasn't heard of it either?
The primary target of the passive dogs (usually Labradors) at tube and train stations is explosives, hence the huge increase in deployment since 7/7. The drugs and firearms that they also pick up are considered by the police an added bonus. Active dogs (usually Springer Spaniels) are used for searching trains, aircraft and cargo.
Training a sniffer dog is EASY. The dog is trained to associate the target smells with a reward (usually a brief play with a ball if he is successful). The passive dogs are trained for different responses such as sit next to a target on a drug mark but lie down on a firearms/explosives mark. There have been attempts to train on knives, but there are too many false positives on tools, bunches of keys etc.
What's really odd about this article is the seemingly complete ignorance of how dogs behave and are trained. Has Amber never owned a dog or had one as a pet as a child? And as for doubting that a dog can smell the difference between people of different races, this is simply ludicrous - they can easily identify relatives of their owners by smell for example.
Any dog owner will tell you how well they can distinguish based on smell - my own German Shepherd can easily tell the difference between his otherwise identical red and green ball based entirely on the fact that they smell slightly different - he obviously can't tell the difference on colour (being colour blind), and if both balls are hidden in a pitch black room he will find the one he is asked for with 100% accuracy.
Oh and Amber, the reason your pothead mate kept getting marked is because he stinks of cannabis - is that really so hard to understand? And as an officer of the court you really shouldn't be associating with habitual drug users.