Borzoid, it is a known fact that some dogs have an inborn sense for this, especially cancer and for seizures. No one can argue that fact. I have witnessed these dogs several times.
As for schH. I have trained 4 GSD's in that and I feel they are safer than your untrained dog. They do not decide for themselves to attack, they need a command or they do not pass. This is not to deny that some schH dogs are trained to detect danger and act on heir own.
As for self trained service dogs, I don't think I've ever heard of this, But I have a friend who works in service dog work for the Lion's Foundation and I can enquire about this. But if a dog is owner trained where would the test be passed? Even the pets and people that Wolfsoul was talking about is run by the Humane society and have the test printed right on their site. They do mention that it is a public access test and the applicants do recieve a certificate of pass or failure.
Bottom line is, if a dog shows any sign of aggression, like growling, biting,raising hackles, showing teeth, it is an automatic failure, regardless of performance.
I think this is the point we are trying to make, these dogs have to be proven for access rights.
But again, I think Fred lanting's books and sites say more than any of us could and prove without a doubt what we are discussing.