If it wasn't on a leash, probably yes. If it WAS on a leash and you didn't control it (which you obviously didn't, since it succeeded in biting someone), probably yes. If the neighbor approached the dog in a way that the dog could have interpreted as threatening to the dog -- like running up to pet it -- the neighbor would have to share some of the blame. This is in my opinion. I am not a lawyer. But you read about this stuff all the time, and it seems like a person is often held liable and sued successfully for some very minor things. So I wouldn't be surprised if you were considered to be at fault.

You might be. When people sue in cases like this, they are encouraged by their attorney's to go after everyone involved most of the time. However, you do have some defense options. Since the dog is not yours, you might claim you were unaware of it's antagonistic behavior and was just trying to help your girlfriend by taking it out for a walk. Since it wasn't your dog you had no way of knowing that "Fluffy" (or whatever its name is) was likely to bite anyone and that you feel bad. Say you wished your girlfriend had told you about it before you kindly offered to walk the dog. Look sweet and pitiful if you can. Now, you're out of luck if you walked the dog frequently and knew it was snippy from your own observations. You might still be able to wriggle out of liability though since you are not the dog owner. One of the other answers talked about your responsibilty to restrain the dog, which you should have done. IF (IF!!!) you had sufficient time to react. If not, make that very clear. If the dog was off the leash and there are leash laws. . .well, you know what they say. . .bottom line, ignorance of the law will not do you any good. However, she is more likely to be liable than you since the care, training, and knowledge of the dog in question is all hers. From now on, let your girlfriends walk their own pooches though :) Good luck.

You both are liable. i hope the dog was on a leash. this will be in your defense. if not, it compounds the situation, that now includes a leash law violation. walking someone's pet, is just like driving someone's automobile. if you are in control of the vehicle or pet, then, you are responsible for the actions of the pet or automobile.