[Janq]

As per the recent dog related issues as posted in OT I wondered what the legal position and precedents might be in MA toward dogs that attack.

Below is what I found:

Commonwealth v. Fettes, 64 Mass.App.Ct. 917 (October 18, 2005). "A dog can be a dangerous weapon. "A dangerous weapon is 'any instrument or instrumentality so constructed or so used as to be likely to produce death or great bodily harm.' Commonwealth v. Farrell, 322 Mass. 606, 614-615 (1948). See also Anderson, Wharton's Criminal Law and Procedure, § 361. There can be little doubt that a dog . . . used for the purpose of intimidation or attack falls within this definition." Commonwealth v. Tarrant, 2 Mass. App. Ct. 483, 486 (1974)."

http://www.lawlib.state.ma.us/guns.html

"Assault and Battery by Means of a Dangerous Weapon. Dangerous Weapon. Dog.
Convicted of assault and battery by means of a dangerous weapon, an eight month old pit bull terrier, on a person sixty years or older, the defendant argues that it was error to deny his motion for a required finding of not guilty made at the close of the Commonwealth's case and renewed at the close of all the evidence. We affirm the judgment."

http://www.masslaw.com/signup/opinion.cfm?page=ma/opin/coa/1121305.htm

As a citizen and dad who takes his family to public areas & trails where there are many folks with all manner of dogs (some off leash) I'd have no compulsion to hurt if not kill an animal/dog if it were trying to harm me or mine.
While as a CCW the above statements and judgement by the Commonwealth of MA support legal use of a weapon (e.g. firearm, pepper spray, single edged folding knife) in a non-property defense. Non property meaning not in the defense of a pet or livestock as they are in this state considered to be 'property' (as is the case in most other states) and by law use of a weapon is not allowed in defense of property.

Just an FYI for MA folks to know & memorize while others might do similar research toward their own state.
Of course defense with a weapon applies only to those MA citizens legally licensed to possess a given defensive product.
Laws toward defensive weapons and possesion do vary state to state.

- Janq