There's only one thing dogs CAN sniff for: A person's scent.
The Newsweek story said the FBI had gotten Dr. Hatfill's scent off the anthrax envelopes.
That was about as dumb an article as we've seen the media print about this case.
In my book I suggest that the bloodhounds had actually been GIVEN Dr. Hatfill's scent because the FBI had lost their tail on Dr. Hatfill at a critical time and needed to determine where he'd been during the period he was missing. The bloodhounds began their sniffing at a Denny's restaurant in Louisiana and checked other spots between there and Dr. Hatfill's apartment, where the dogs were finally allowed to "find" their prey.
Huh? I don't know if dogs can smell anthrax, but I know that they can be trained to sniff for things other than a human scent. The dogs you see in airports can sniff for things such as contraband food items and certain types of chemical explosive compounds.