The fact remains that the dogs could find neither the explosive or residual scent ... nothing is reported about fully trained animals being brought in ... but I bet they were.
Perhaps there was no residual scent in a freight station? As in, the C-4 was placed in a lorry container, which had been driven off-site.
Or it had never been placed in the first instance?
I enjoy watching programmes about all sorts of dog uses. Australia and NZ use them to screen incoming passengers and mail.
It's amazing how many times a dog alerts. The passenger then denies any drug use or possession. The officers then use various tools to screen for drugs. The results come up positive. The passenger then changes his story, either to yes he has used drugs recently, or to yes he has been in contact with people using drugs.
What happens thereafter is simple. If the officer find drugs, the person is charged. If the officer does not find drugs, the person is free to go.
I have somewhat more confidence in the dogs and the screening tools than I have with someone who lies with as many teeth ....