Dangerous dog laws, including the dog bite law, vary from state to state, with different definitions and outcomes for owners.

In Massachusetts, the dangerous dog laws are outlined under Massachusetts General Laws Chapter 140, Sections 136A-174F. These laws define a 'dangerous dog' as one that either without justification attacks a person or domestic animal causing physical injury or death, or behaves in a manner that a reasonable person would believe poses an unjustified imminent threat of physical injury or death to a person or domestic animal. The law does not apply to a dog that reacts to another animal or to a person if the dog is responding to pain or injury, or is protecting itself, its offspring, or its owner. If a dog is deemed dangerous, the owner may be ordered to take remedial actions, which can include confinement, restraint, or even euthanasia of the dog in extreme cases. Regarding dog bites, Massachusetts operates under a 'strict liability' statute, specifically Massachusetts General Laws Chapter 140, Section 155. This means that the owner or keeper of the dog is held liable for any damage caused by the dog biting a person, regardless of the dog's former viciousness or the owner's knowledge of such viciousness. There are exceptions to this rule, such as if the victim was trespassing, committing another tort, or teasing, tormenting, or abusing the dog. It's important for dog owners in Massachusetts to understand these laws to ensure they are in compliance and to understand their potential liability in the event their dog injures someone.