A number of people find my blog by searching for something like "do service dogs bite" or "when service dogs bite" or "what if a service dog bites."
Well, a service dog is still a dog, and I imagine any dog will bite if sufficiently provoked.
The thing about a service dog, though, a properly selected and trained service dog, is that he would require a lot of provocation before he would bite.
Service dogs should have a certain kind of temperament. When a professional service dog trainer or an animal behaviorist evaluates a dog to see if he might make a good service dog, they do things like touch the dog all over to see if the dog tolerates it. Of course, there is a lot more to an assessment than just that. That's why, even if someone plans to train their own service dog, it's a very good idea to have a professional at least help in the selection process. When I was having trouble finding a service dog program and thinking of training my own service dog (with lots and lots of help from a professional trainer), the trainer I was talking to was going to help me choose the dog.
But anyway. A dog that is quick to be startled or upset or that is really sensitive to being touched in certain ways or certain places probably wouldn't make a good service dog. A service dog should have a pretty easy-going temperament and not be quick to growl or snap or bite, even if he really doesn't like something.
Like Isaac. I think, for Isaac to be provoked into biting someone, you would have to restrain him so that he couldn't get away from you and then do something that didn't just bug him but that was pretty painful or otherwise unpleasant.
If Isaac doesn't like something, his first reaction is typically to try to move away from it. He doesn't necessarily try to even get away from the person doing it, just to move that part of his body out of reach. For instance, he doesn't really like his feet handled a lot. He is happy to shake hands, but if you want to touch his toes a lot, he will try to pull his paw away. He doesn't try to walk away, he still wants attention and wants you to pet him and play with him and stuff, he just prefers you stop touching his toes. Or, he doesn't like his talk messed with very much, either. You can pet it a little but if you try to play with it a lot, he will turn his body so his head is closer to you and his tail is further away. Then he will probably try to kiss you. Because he's not mad at you for touching his tail, he'd just rather you scratch behind his ears.
As long as you're not really hurting him, though, he will tolerate you doing something he doesn't like. He allows me to hold his foot and cut his toenails, even though he'd rather I didn't. He will attempt to pull his foot away sometimes but I just tell him to stay and he sits there and holds still. He just gives me the sad puppy eyes about it.
But he's been trained to cooperate. So in addition to having the right sort of temperament, he has training that makes him unlikely to bite.
There is a man at the nursing home we visit that likes to pet Isaac. He doesn't pet very gently, though. Now, Isaac is not real picky about how he gets petted. Cayenne sure is! Probably most cats are pickier than most dogs, but she is really picky. If you don't do it right, she just won't let you pet her at all. But Isaac doesn't much care. He has favorite places and ways to be petted, but he is happy with almost any sort of petting. But this particular man has trouble stroking. He doesn't pat, either. He kind of scrunches his fingers together and sometimes he sort of pinches. I don't think he means to and I don't think he understands what he's doing, but Isaac doesn't much like it. He will tolerate it for a minute or so, but when it gets too pinchy, he backs away.
How long would Isaac tolerate it if I didn't allow him to back away? I don't know.
And that's the other thing about service dogs and making sure they don't bite. The owner has to pay attention. When Isaac backs away, especially if he does it more than once, he is saying, "Hey, I don't like this." He would probably stand still for it if I told him to, at least for a while. But if I didn't listen when he told me he really doesn't like something, he might start telling me in a louder, more insistent way. He might growl, for instance. Or snap at the man. And if that didn't work, he might feel he had no other choice but to bite. That would be his last resort, though, and I would consider that my fault.