Drug sniffing dogs are trained to sniff out a specific terpene that occurs in cannabis.
The thing is, it is present in many other foods and plants too.
I believe drug sniffing dogs at traffic stops should be illegal. A random guess has the same or better probability of being correct.
Terpene... shmerpene.
A dog will get excited if it pleases his master, if a bitch runs across his path, or ... if he smells a ham sandwich.
As you pointed out, there’s a lot of false positives.