We are training out dogs using birch and cloves. But having been trained to sniff anything out they are much more aware of other smells and their possibilities of earning a reward. Dogs can even be trained to sniff out cancer cells.
But to be useful in law enforcement the dog needs a handler who knows what his dog is looking for, finds rewarding, and need to be looking in the right places. Looking for the scent of a missing child in the child's home makes no sense unless the dog is able to distinguish only cadaver smell. If it also hits on poop... no go. Also, the cadaver smell doesn't get interesting until the person has been dead for a while, so... Casey's trunk? Sure. A floor where a body lay for 1/2 hour or so? No.