Procedure: Action of trespass for assault and battery. Plaintiff won in trial court. Defendant appealed to Mass SC.

Issue: How far can the party whose unconscious act of striking the P in the eye be responsible for it? Should have the jury been instructed D was responsible for his actions because separating the dogs was not necessary?

Rule: When actions such as this are truly unintentional in a lawful act, the defendant cannot be held liable.

Holding: D was engaged in a lawful act of trying to separate two fighting dogs and in no way intended to hit P. Because this battery was unintentional and result of pure accident, the defendant cannot be held liable.

Rationale: The jury should not have been instructed to assume that because separating the dogs was not a necessary act, D was liable for all accidents. Instead this should be seen as D performing a lawful act and P becoming an innocent victim. D must be charged with some fault such as negligence, carelessness, or want of prudence in order for P to sustain the burden of proof. Both D and P were using ordinary care: kind and degree of care which prudent and cautious men would use.