If your dog is on the property and they were not invited I don't see how you could be held for anything.
But, if your dog runs into the road to bite and the people were invited on your property you are liable.
Check your township or city ordances on trespassing dogs and trespassing people.
Then check to see if your dog can protect his property
Many townships and cities have the same laws but you better double check.
A police report to the incident is wise to do. especially if you have a witness with you that can verify this is what happened.
I would fence in the yard

Dieta answered on 2/28/10. Helpful? / 1

Definetly not, their dog is on your property, where it obviously had no business, it's not your problem.

Buddy answered on 6/4/10. Helpful? / 0