In Massachusetts, penalties are established for "assault" upon a person, but apparently there is no definition of "assault". So, what constitutes an assault could apparently be open to interpretation. For example, if a robber attacks a person and the victim injures the robber, we could envision the prosecutors indicting the robber's target because the robber being the one injured, would mean that the victim could be prosecuted for a higher charge.

In other words, why would a prosecutor charge a low class robber for simple assault, when they could charge the victim for assault and batter, or mayhem, much more serious charges? Or, imagine that the victim kills the robber. Now, the prosecutor cannot even charge robber, because he is dead, so what will the prosecutor do? Charge the victim for manslaughter of course, or even second degree murder!

The whole root of the problem seems to be that there is no legal definition of assault, at least that I could find, essentially allowing the prosecutor to invent whatever definition of assault he likes. Is there anything to prevent this?

  • Are you assuming that the statutes must contain definitions for all terms? So the question would be equally applicable to murder, manslaughter, rape.
    – user6726
    Feb 18, 2017 at 0:36

2 Answers 2


Assault is a common law crime, and while common law offenses cannot be recognized at the federal level (US v. Hudson and Goodwin, 11 U.S. 32), the states may abolish them or not. Massachusetts recognizes common law offenses, as well as General Laws offenses. The exact meaning of "assault" emerges from centuries of usage under law, and the crime of assault is not different from the tort of assault. The Restatements of Torts have suitable definitions of battery and assault, so that there isn't vast leeway to define a scowl as an assault. Drawing on these various definitions "out there", Massachusetts conveys the essential concepts to a jury in the form of instructions, saying

An assault may be committed in either of two ways. It is either an attempted battery or an immediately threatened battery. A battery is a harmful or an unpermitted touching of another person.

There is further elaboration (via jury instruction) here. In Commonwealth v. Burke, 390 Mass. 480, the court says "Our analysis demonstrates, by recourse to the common law, that a physically harmful touching is a battery, and consent is immaterial"; that is, the definition comes from the common law, not a statute (the penalty, though, comes from statute). Not all crimes are defined in common law, such as failure of a sex offender to register, which is criminalized in G.L c. 6, §178h(a).

The general scheme for the tort of battery is a bit convoluted, because it amounts to any touching, unless permitted, at which point there are a number of conditions that constitutes "being permitted". Self defense is one of those. Rather than build "self defense" into the definition of "battery", "battery" is left very simply, and the law prohibits unpermitted battery. The Massachusetts model instructions for self defense are here, again summarizing a few centuries of wisdom over what is and is not proper self-defense. A clear example would be that it is not self defense to intentionally kill a person who blocks your passage through a doorway. One of the conditions for using non-deadly force is that the Commonwealth must prove that "the defendant did not reasonably believe he (she) was being attacked or immediately about to be attacked, and that his (her) safety was in immediate danger"; they must also prove that you "did not do everything reasonable in the circumstances to avoid physical combat before resorting to force"; and "that the defendant used more force to defend himself (herself) than was reasonably necessary in the circumstances".

You can compare this to Washington state law which has a statutory statement of "self defense", which says that force is not unlawful

Whenever used by a party about to be injured, or by another lawfully aiding him or her, in preventing or attempting to prevent an offense against his or her person, or a malicious trespass, or other malicious interference with real or personal property lawfully in his or her possession, in case the force is not more than is necessary

This results in a particular set of jury instructions that correspond in various ways to the Massachusetts instruction; though I don't want to imply that they are the same. The Washington instruction refers to

such force and means as a reasonably prudent person would use under the same or similar conditions as they appeared to the person, taking into consideration all of the facts and circumstances known to the person at the time of [and prior to] the incident.

which is another way of slicing up the elements of the Massachusetts self defense defense.

  • My concern is that if I injured or killed someone who attacked me that I would be prosecuted and I am trying to figure out what there is in the law that would protect me from this outcome.
    – Cicero
    Feb 18, 2017 at 2:48
  • Yes, there is, but the protections are rather vague and amount to throwing yourself n the mercy of the court and jury.
    – user6726
    Feb 18, 2017 at 3:18
  • That is not a legal protection.
    – Cicero
    Feb 18, 2017 at 3:49

The legal definition of assault is:

  1. Intentionally putting another person in reasonable apprehension of an imminent harmful or offensive contact. No intent to cause physical injury needs to exist, and no physical injury needs to result. So defined in tort law and the criminal statutes of some states.

  2. With the intent to cause physical injury, making another person reasonably apprehend an imminent harmful or offensive contact. Essentially, an attempted battery. So defined in the criminal statutes of some states.

  3. With the intent to cause physical injury, actually causing such injury to another person. Essentially, the same as a battery. So defined in the criminal statutes of some states, and so understood in popular usage.

In your example, the victim was using self-dense against the robber, so the victim probably won't be charged for assault.

  • It doesn't say that in the laws. All that it says is that anybody who causes "bodily harm" to another can be put in jail for up to 3 years.
    – Cicero
    Feb 17, 2017 at 23:07

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