>Well, in the case of pups, there may have been more than one
>sire.

In the cases I'm talking about, the breeding is carefully controlled. There are not many dogs that have all the desirable traits to be a service dog, so when the breeders of them get those good traits, they don't let their bitch be mated with more than one sire.

Even under carefully controlled conditions, the bitch can still throw a dangerous dog irregardless of environment.