Self-Defense in Massachusetts | Reasonable Force, Duty to Retreat, and Adjutant Evidence

Self-defense is not an excuse. It is a complete defense to crimes of violence. It is also a legal justification the Commonwealth must disprove; a defendant who properly puts the issue before a jury or trial judge has no burden to prove self-defense. Again, when self-defense is properly raised in a Massachusetts criminal case, the burden never shifts to the accused. The prosecution must prove, beyond a reasonable doubt, that the defendant did not act in self-defense, and if it fails to do so on even one element, the defendant is entitled to an acquittal. Commonwealth v. A Juvenile, 396 Mass. 108, 113 to 114 (1985).

This critical principle reshapes the entire case, because it means a successful self-defense case is often built not by proving what happened, but by making the Commonwealth’s account of what happened impossible to sustain to a certainty. Serpa Law Office has raised and won self-defense in assault, assault and battery, weapons, and homicide-adjacent cases across the Massachusetts District, Boston Municipal, and Superior Courts for thirty years.

The Three Elements of Self-Defense

Massachusetts self-defense is a common-law doctrine, delivered to juries through the Model Jury Instructions rather than a single statute. For a case involving non-deadly force, a defendant is entitled to a self-defense instruction if any view of the evidence would support a reasonable doubt that: first, the defendant had a reasonable concern for personal safety; second, the defendant used all reasonable means to avoid physical combat; and third, the degree of force used was reasonable in the circumstances, with proportionality being the touchstone for assessing reasonableness. Commonwealth v. Franchino, 61 Mass. App. Ct. 367, 368 to 369 (2004); Commonwealth v. King, 460 Mass. 80, 83 (2011). The evidence is viewed in the light most favorable to the defendant when the judge decides whether the instruction must be given, which is why preserving the right to that instruction is a central task of the defense from the first witness forward.

The concern for safety must be grounded in an overt act by the other person, a blow, a gesture, a movement, not in words alone. Commonwealth v. Harris, 464 Mass. 425, 433 to 436 (2013), cautions that instructions treating a person who provokes a confrontation as forfeiting self-defense are overbroad unless they make clear that nonthreatening words alone do not qualify a defendant as the first aggressor. The distinction matters in the ordinary argument-that-turned-physical case, because the Commonwealth will often try to cast the person who spoke first, or loudest, as the aggressor who gave up the right to defend himself.

Deadly Force and Non-Deadly Force Are Different Standards

Massachusetts treats the two levels of force under separate and mutually exclusive standards, and the difference is decisive. Commonwealth v. Walker, 443 Mass. 213, 217 (2005). Non-deadly force, a push, a shove, a punch, is justified at a lower level of danger: a genuine and reasonable concern over personal safety. Commonwealth v. Baseler, 419 Mass. 500, 502 to 503 (1995). Deadly force, meaning force intended or likely to cause death or great bodily harm, is justified only where the defendant actually and reasonably believed he was in imminent danger of death or serious bodily injury and could save himself only by using that force. Commonwealth v. Grassie, 476 Mass. 202, 210 (2017); Commonwealth v. Pike, 428 Mass. 393, 396 (1998).

Because the standards are mutually exclusive, it is reversible error for a judge to give a deadly-force instruction where the evidence called for a non-deadly-force instruction, since doing so wrongly raises the danger threshold and lowers the Commonwealth’s burden to disprove the defense. Baseler, 419 Mass. at 503 to 504. Getting the court to charge the jury on the correct standard is frequently the whole contest in an assault and battery trial, because a client who threw a single punch in response to being grabbed is entitled to be judged by the reasonable-concern standard, not the imminent-death standard the Commonwealth would prefer the jury apply.

The Duty to Retreat

Massachusetts is not a stand-your-ground state. Outside the home, a person must use every reasonable avenue of escape available before resorting to force, and the failure to retreat when a safe path was available can defeat the defense. Commonwealth v. Pike, 428 Mass. 393, 399 (1998); Commonwealth v. Mercado, 456 Mass. 198, 209 (2010). This is not an absolute duty: a person need not place himself in additional danger, exhaust every conceivable escape route, or use every means of flight short of death before defending himself. Commonwealth v. Benoit, 452 Mass. 212, 226 to 227 (2008). But if a safe exit was reasonably available and the defendant did not take it, the Commonwealth will use that fact to argue the force was not justified. The Appeals Court applied the rule starkly in Commonwealth v. Leoner-Aguirre, 94 Mass. App. Ct. 581 (2018), where a defendant who shot a victim in the back as the victim fled a public street lost his self-defense claim precisely because he had a clear opportunity to retreat and did not.

Whether a defendant availed himself of all reasonable means to avoid combat is decided on the totality of the circumstances, and the relevant considerations include how close the threat was, the relative size and number of the participants, the presence of weapons, the location, and whether summoning help or simply walking away would have ended the danger. The retreat question is where many otherwise strong self-defense cases are won or lost, and it is the point on which the defense investigation, the scene, the exits, the distances, the timing, does the most work.

The Castle Law: No Duty to Retreat in the Home

The single statutory exception to the duty to retreat is the castle law, G.L. c. 278, § 8A. It provides that where an occupant of a dwelling is charged with killing or injuring a person who was unlawfully in that dwelling, it is a defense that the occupant was in the dwelling, reasonably believed the intruder was about to inflict great bodily injury or death on the occupant or another person lawfully present, and used reasonable means to defend against that threat. The statute states plainly that there is no duty on the occupant to retreat from a person unlawfully in the dwelling. The reasonableness and proportionality requirements still apply; what the castle law removes is only the obligation to flee first.

The doctrine is narrower than most people assume, and three limits recur in real cases. First, it protects against unlawful intruders only. It does not eliminate the duty to retreat from a person who is lawfully in the home, a guest, a family member, a cohabitant, even when that person launches a life-threatening attack. Commonwealth v. Peloquin, 437 Mass. 204, 208 (2002). A person who entered lawfully but then refuses a demand to leave can become a trespasser under G.L. c. 266, § 120, which can change the analysis, but that determination is rarely clean in the middle of a violent encounter. Second, “dwelling” means the space a person actually occupies and exclusively controls; Massachusetts courts have held that common hallways, shared stairwells, porches, and driveways in multi-unit housing fall outside the castle law’s protection, so the confrontation’s exact location can decide whether the duty to retreat applied. Third, the belief in the threat must still be reasonable and the force still proportional; the castle law is not a license to use deadly force against every unwanted entry.

Self-Defense in Domestic Violence Cases

Nowhere does self-defense arise more often, or with more complexity, than in domestic violence prosecutions. The person who called the police is not always the person who started the violence, and the person arrested is not always the aggressor. Massachusetts law gives the defense in these cases tools that exist in few other contexts, and using them well can be the difference between a conviction that ends a career or an immigration status and an acquittal or a dismissal.

The starting point is the same burden that governs every self-defense case: the Commonwealth must disprove self-defense beyond a reasonable doubt, and in a household case that often means disproving it against a history the prosecution would rather the jury never hear. Where the client acted with non-deadly force, the reasonable-concern standard governs, and a genuine and reasonable fear for immediate personal safety, formed against a background of prior abuse, is exactly what the defense is entitled to place before the jury.

Two bodies of law do the heavy lifting. The first is the defendant’s knowledge of the complainant’s prior violence and threats. To show the reasonableness of the defendant’s apprehension, the defense may introduce the complainant’s prior acts of violence, prior threats against the defendant, and reputation for violence, provided the defendant knew of them at the time. Commonwealth v. Pidge, 400 Mass. 350, 353 (1987); Commonwealth v. Edmonds, 365 Mass. 496, 499 to 501 (1974); Mass. G. Evid. § 404(a)(2)(C). In a relationship marked by escalating abuse, that history is not background; it is the reason a reasonable person in the defendant’s position perceived danger in a movement an outsider might read as harmless.

The second is statutory. G.L. c. 233, § 23F specifically authorizes, in support of a claim of self-defense or defense of another, evidence that the defendant is or has been a victim of abuse, together with expert testimony on the common effects of abuse, sometimes described as battered-person syndrome. Section 23F allows the jury to understand why a person subjected to a pattern of abuse may perceive the imminence and severity of a threat differently than a stranger to the relationship would, and why that perception can be reasonable. This is powerful, humanizing evidence, and it is admitted on the defendant’s terms, but it requires early identification of the issue, the right expert, and careful groundwork, none of which can be assembled at the last minute.

Prior Aggression by the Alleged Victim: Adjutant Evidence

One of the most consequential developments in modern Massachusetts self-defense law addresses the situation where the defendant did not know of the complainant’s violent history at the time, or where what matters is not the defendant’s state of mind but the simple factual question of who started the fight. In Commonwealth v. Adjutant, 443 Mass. 649 (2005), the Supreme Judicial Court held that where a claim of self-defense is raised and the identity of the first aggressor is genuinely in dispute, the trial judge has discretion to admit evidence of the alleged victim’s specific prior acts of violence, whether or not the defendant knew of them at the time.

The logic is direct and, once stated, difficult to answer. A person with a documented history of initiating violence is more likely to have acted in conformity with that history and thrown the first blow. Adjutant, 443 Mass. at 664. Because that inference does not depend on what the defendant knew, the evidence is admitted for a distinct purpose from the reputation and knowledge evidence described above: not to show the reasonableness of the defendant’s fear, but to prove, as a matter of fact, that the complainant was the aggressor. The court favored concrete, specific acts of violence over general reputation evidence, reasoning that juries should be trusted to weigh real incidents in deciding who probably started the confrontation. Adjutant, 443 Mass. at 664 to 665.

The doctrine has grown in the two decades since, and the current contours matter to any real case:

The “first aggressor” includes the first to escalate to deadly force. The term is not limited to whoever threw the first punch. It reaches the person who first escalated a non-deadly confrontation into a deadly one by the threat or use of deadly force. Commonwealth v. Chambers, 465 Mass. 520, 528 to 530 (2013); Commonwealth v. Souza, 492 Mass. 615 (2023). So even where it is undisputed that the defendant swung first with his fists, Adjutant evidence can still be admissible on the separate question of who first reached for the knife or the gun.

The whole incident, not just the opening move, can come in. Where the victim initiated the violence, the entirety of the violent event the victim began is potentially admissible, so the jury sees a full picture rather than a fragment. Commonwealth v. Deconinck, 480 Mass. 254, 263 (2018); Souza, 492 Mass. at 617.

Acts before or after the charged offense qualify. The specific acts of violence admissible under the Adjutant rule may have occurred either before or after the offense on trial. Commonwealth v. Andrade, 496 Mass. 144, 147 to 148 (2025); see Commonwealth v. Chambers, 465 Mass. 520 (2013) (assault occurring after the charged incident admissible).

The judge’s discretion cuts both ways, and notice is mandatory. Adjutant evidence is admitted only in the trial judge’s discretion, after weighing probative value against prejudice, and a judge may exclude it even where the first-aggressor question is disputed. Souza, 492 Mass. at 626; Commonwealth v. Rateree, 495 Mass. 611, 621 (2025). A defendant who intends to offer it must give advance notice to the court and to the Commonwealth of the specific evidence, ordinarily through the pretrial conference report, so preserving the issue is a matter of procedure as much as proof.

The Commonwealth can rebut. If the defense opens the door with specific acts of the victim’s violence, the prosecution may answer with evidence of the victim’s reputation for peacefulness, Adjutant, 443 Mass. at 666 n.19, and with specific acts of the defendant’s own prior violence, Commonwealth v. Morales, 464 Mass. 302, 310 to 311 (2013). This is why the decision to pursue an Adjutant theory is a strategic one, taken with full knowledge of what it invites in response, and not a reflex.

The Adjutant Disclosure: Getting the Evidence Before the Jury

Adjutant evidence is worthless if it is not preserved, and preservation is a procedural discipline that begins long before trial. Because the rule requires the defense to notify the court and the Commonwealth in advance of the specific acts it intends to prove, the obligation is ordinarily satisfied through the pretrial conference report and, where needed, a motion in limine that identifies each incident with particularity. The groundwork is investigative: obtaining the complainant’s record of prior violent conduct, restraining orders taken out against the complainant by others, police reports of incidents in which the complainant was the aggressor, and witnesses to those incidents. Not all of it will be admissible, hearsay limits still apply, and a police report describing a prior incident is not automatically admissible merely because it is relevant under Adjutant, Commonwealth v. Deconinck, 480 Mass. at 263 to 264, but the incidents must be identified, investigated, and disclosed in time for the court to rule and the Commonwealth to respond. A defense that waits until trial to raise a victim’s violent history has usually already lost the ability to use it. Serpa Law Office builds the Adjutant record from the earliest stage of a self-defense case, because the disclosure deadline, like so much else in these cases, rewards the lawyer who prepared for trial from the first day.

Defense of Another

A person may use reasonable force to defend a third person under principles that track the law of self-defense: the defender may use the degree of force the person being protected would have been entitled to use, judged by what the defender reasonably believed was necessary. The same distinctions between deadly and non-deadly force, the same proportionality requirement, and the same burden on the Commonwealth to disprove the justification beyond a reasonable doubt all apply. Defense of another arises constantly in the real world of bar fights, family altercations, and street confrontations, and it is a distinct justification from self-defense, with its own instruction, that must be requested and preserved on its own terms.

The Offenses Where Self-Defense Applies

Self-defense and defense of another are potentially available across the full range of Massachusetts crimes that involve the use of force, and Serpa Law Office raises them wherever the facts support the instruction, including:

• Assault and battery on a family or household member under G.L. c. 265, § 13M, the charge in which self-defense, prior-abuse evidence, and Adjutant evidence most often converge.
• Simple assault and battery under G.L. c. 265, § 13A, the most common charge in which the reasonable-concern, non-deadly-force standard controls.
• Assault and battery with a dangerous weapon under G.L. c. 265, § 15A, where the deadly-force standard and the proportionality of the response are usually the whole case.
• Strangulation or suffocation under G.L. c. 265, § 15D, frequently charged in household cases where the question of who first became violent is genuinely disputed.
• Firearms and weapons charges, where the lawful defensive use of force can bear on the underlying conduct.
• Homicide offenses, including the manslaughter and murder cases in which the Adjutant rule itself was forged, where self-defense and defense of another are litigated at their highest stakes.

Why Early Defense Work Decides Self-Defense Cases

A self-defense case is not saved by an explanation offered at sentencing; it is built from the first hours. The scene changes, the exits and distances that decide the retreat question are best documented immediately, witnesses to the complainant’s aggression scatter, injuries on the defendant that corroborate a defensive account fade within days, and the Adjutant and § 23F records take time to assemble and must be disclosed on the court’s schedule. Just as important, what the client says to the police in the first hour can foreclose a self-defense claim that the facts would otherwise have supported, which is why the right to remain silent is never more valuable than in the aftermath of a violent encounter the client did not start. Serpa Law Office prepares every self-defense case as a trial case from the first day, because the Commonwealth’s burden to disprove the justification beyond a reasonable doubt is only leverage in the hands of a lawyer ready to make it try.

If you or a family member has been charged after defending yourself or another person, the account you give and the evidence you preserve in the first days will shape everything that follows. Call Serpa Law Office at 617.936.0201 for a free and confidential consultation. Boston office: 20 Park Plaza #400A. Quincy office: 500 Victory Rd., Suite 400A. Available 24 hours a day.

Related Serpa Law Office Resources

• Domestic Violence Defense in Massachusetts
• Assault and Battery on a Family or Household Member (G.L. c. 265, § 13M)
• Strangulation and Suffocation (G.L. c. 265, § 15D)
• Your Right to Remain Silent in Massachusetts
• Illegal Searches and Seizures
• Firearms and Weapons Charges
• Criminal Defense Practice Areas
• Massachusetts Criminal Defense Results
• Massachusetts District Courts and Boston Municipal Court