Where was the dog when he attacked?
Where was the people?
Why were they around the dog?
Was the dog supervised by you?
Did you have proper notification of beware of dog signs?
The main issue I see here is a "He said She said" thing............bascly it is your sons word against the other people. Since he had the dog out and about, the first thing the judge will ask is if you felt the dog may be a danger why was he not properly contained away from people. The actions you took warning people to stay away from the dog is admitting that you thought he may bite. In essence placing you in between a rock and a hard place.
The humane society followed there own rules and regulations by taking the dog since it was involved in two incidents. Caging dogs rarely cause increased aggression unless it is for a extended period of time with little or no contact so your dog is unlikely to become more aggressive based on his housing right now. So this may be of little concern to your family's wellbeing right now.
Basically what will happen is the humane society will run some exercises with the dog to determine if he is in fact aggressive. Once done they will supply a report to the judge who will decide the fate of the dog. Bear in mind the judge can issue for dog to be put to sleep if he feels the dog is a threat to society. You will likely be fined in both incidences....the second being a larger fine since you allowed the dog out once again after the first incident. The person that was bitten also has the right to file a civil suit against you for damages as well.
Right now you will want to stay in contact with the humane society to inquire as to your dogs status and to determine what the courts are going to do in this case.
I wish you the best,
DISCLAIMER: Answers from Experts on JustAnswer are not substitutes for the advice of an attorney. JustAnswer is a public forum and questions and responses are not private or confidential or protected by the attorney-client privilege. The Expert above is not your attorney, and the response above is not legal advice. You should not read this response to propose specific action or address specific circumstances, but only to give you a sense of general principles of law that might affect the situation you describe. Application of these general principles to particular circumstances must be done by a lawyer who has spoken with you in confidence, learned all relevant information, and explored various options. Before acting on these general principles, you should hire a lawyer licensed to practice law in the jurisdiction to which your question pertains.
The responses above are from individual Experts, not JustAnswer. The site and services are provided “as is”. To view the verified credential of an Expert, click on the “Verified” symbol in the Expert’s profile. This site is not for emergency questions which should be directed immediately by telephone or in-person to qualified professionals. Please carefully read the Terms of Service (last updated February 8, 2012).