Self-Defense and Mutual Combat in Massachusetts Domestic Violence Cases

Two partners who live together argue in the kitchen of their apartment. When one partner grabs the second partner by the arm, the second partner pushes the first partner away to break free. When the police arrive, both partners have marks on their arms. The officers will sometimes arrest who they surmise was the “first aggressor” partner, or the officers may arrest both partners. They then face a charge of assault and battery on a family or household member, even though the evidence may show that the accused person acted in self-defense.

Once the evidence at trial raises self-defense, the Commonwealth must prove beyond a reasonable doubt that the defendant did not act in self-defense. Commonwealth v. King, 460 Mass. 80, 83 (2011). The sections below explain how self-defense applies when both people used force in a domestic incident, what mutual combat means, how a person must try to avoid a fight in a shared home, and what evidence can show who started the fight and who acted in self-defense.

Attorney Joe Serpa has practiced Massachusetts criminal defense since 1995. He defends people charged with assault and battery on a family or household member and other domestic violence offenses in the district courts and the Boston Municipal Court.

Self-Defense Is a Complete Defense to a Domestic Assault Charge

Self-defense is a trial issue. At trial, the judge instructs the jury on self-defense when any view of the evidence, taken in the light most favorable to the defendant, supports a reasonable doubt about whether the defendant acted in self-defense. Commonwealth v. Pike, 428 Mass. 393, 395 (1998). King, 460 Mass. at 83.

When self-defense is an issue at trial, the defendant has no burden to prove self-defense. The Commonwealth must prove beyond a reasonable doubt that the defendant did not act in self-defense. If the Commonwealth fails to prove that the defendant did not act in self-defense, the jury must find the defendant not guilty.

The defendant does not have to testify at trial in order to raise self-defense. To raise self-defense, the defendant may rely on the testimony of the Commonwealth’s own witnesses, defense witnesses, or on evidence the defense presents, or on both kinds of evidence. Commonwealth v. Galvin, 56 Mass. App. Ct. 698, 699 (2002). Commonwealth v. Toon, 55 Mass. App. Ct. 642, 650-651 (2002). Very often, however, the defendant is the only other witness. The client must make the very difficult decision whether to testify, after advice from counsel.

The firm’s page on self-defense in Massachusetts explains the general rules, including defense of property and force against a police officer.

What the Commonwealth Must Prove for Nondeadly Force

Most domestic assault charges involve pushing, grabbing, or hitting, which is nondeadly force. To defeat a claim of self-defense with nondeadly force, the Commonwealth must prove at least one of the following five facts beyond a reasonable doubt. District Court Model Jury Instruction 9.261 (rev. Feb. 2026).

• The defendant did not actually have a concern for the defendant’s own immediate safety.
• A reasonable person in the defendant’s circumstances would not have had that concern.
• The defendant did not take all reasonable steps to avoid physical combat before using force.
• The defendant used more force than was reasonably necessary.
• The defendant was the first to use or threaten force and did not withdraw in good faith and clearly communicate, by words or conduct, the intention to end the confrontation.

In a domestic case, the verdict often depends on whether the defendant could have walked away before using force and whether the defendant used more force than the situation required.

Deadly force is force intended or likely to cause death or serious bodily harm, such as the use of a knife or a firearm. A person may use deadly force in self-defense only if the person reasonably believed that he or she was in imminent danger of death or serious bodily harm and that no other means would prevent that harm. Pike, 428 Mass. at 396. District Court Model Jury Instruction 9.262 (rev. Feb. 2026).

When Both People Used Force or Both Were Arrested

The police officer at the scene decides only whether there is probable cause to make an arrest. A judge or jury will later decide whether the Commonwealth has proved beyond a reasonable doubt that the defendant did not act in self-defense.

When no restraining order is in effect, G.L. c. 209A, § 6(7) provides that arrest is the preferred response when an officer has probable cause to believe that a person committed an assault and battery or another misdemeanor involving abuse. An officer who arrests both people must submit a detailed written report setting out the grounds for each arrest. Id. The state’s Public Safety Office guidelines instructs officers to identify the dominant aggressor and strongly discourage dual arrests. Executive Office of Public Safety and Security, Domestic Violence Law Enforcement Guidelines § 8, at 28 (2017).

When both people were arrested, defense counsel reviews the officer’s written report for statements that may show that the other person started the fight.

When the Commonwealth charges both people, each person may also have a privilege against self-incrimination. A complaining witness charged based on the same incident may refuse to answer questions that could incriminate themselves. Mass. G. Evid. § 511(b). The Commonwealth may still go forward with other evidence, such as a 911 recording or body camera video. The firm’s page on when the alleged victim will not testify explains how the Commonwealth proceeds without the alleged victim’s testimony.

Mutual Combat Means an Agreement to Fight

In Massachusetts self-defense law, mutual combat means a fight that both people intentionally and voluntarily took part in. When two people mutually engage in a fistfight, neither one is ordinarily acting in self-defense because neither one used all reasonable means to avoid combat. District Court Model Jury Instruction 9.260A, note 13 (rev. Oct. 2024). Commonwealth v. Bertrand, 385 Mass. 356, 362 (1982).

An attack and a defensive response is different. Self-defense, not mutual combat, occurs when one partner attacks their partner, and the other partner pushes back to get free or avoid more violence. When a domestic violence trial has such evidence, the jury decides whether the two people were in a mutual fight or whether one person attacked first and the other person defended themselves.

Withdrawal and Escalation to Deadly Force

Ordinarily, a person who is the first aggressor cannot claim self-defense. Sometimes, however, a person who started the confrontation can regain the right of self-defense. That person must withdraw from the conflict in good faith and clearly communicate, by words or conduct, the intention to end the confrontation. Commonwealth v. Maguire, 375 Mass. 768, 772 (1978). District Court Model Jury Instruction 9.261. If the other person continues the attack after the withdrawal, the person who withdrew may use reasonable force to defend against the continued attack. That second escalation of violence then permits the initial aggressor to claim self-defense.

Likewise, a person in mutual combat can also use self-defense when the other person escalates the fight to a higher level of violence, such as deadly force. Self-defense can be used if the escalation is contrary to the original understanding between the two people.

If the person who agreed to the fistfight reasonably believes that the other person has escalated the fight to deadly force, usually by introducing a weapon, self-defense is a valid and lawful response. Commonwealth v. Barber, 18 Mass. App. Ct. 460, 463 (1984), S.C., 394 Mass. 1013 (1985).

In Barber, the Supreme Judicial Court held that the defendant was entitled to a self-defense instruction because the jury could find that the fight had escalated from a fistfight to a fight in which the defendant’s use of a knife was warranted. The defendant must still have been unable to avoid the combat and must have used no more force than necessary. Barber, 18 Mass. App. Ct. at 464.

Self-Defense in a Shared Home

A person attacked at home by a partner who also lives there must still take all reasonable steps to avoid physical combat before using force. Under the castle doctrine, G.L. c. 278, § 8A, a resident has no duty to retreat unless the attacker is unlawfully in the home. Commonwealth v. Peloquin, 437 Mass. 204, 208 (2002).

When both people live in the home lawfully, the ordinary rule applies to a fight between the two people who live there. Commonwealth v. Shaffer, 367 Mass. 508, 511 (1975). In other words, a co-resident must still take every measure to avoid the fight and may not “stand their ground” simply because they are at home.

The duty to avoid combat requires only action that is reasonable in the circumstances. A person does not have to retreat at the risk of their own safety. Shaffer, 367 Mass. at 511-512. The judge should also instruct the jury that the location of the assault, in the defendant’s own home, is a factor of major importance in deciding whether the defendant used all proper means to avoid using deadly force. Id. The firm’s page on self-defense in Massachusetts explains the castle law in more detail.

Battered Women: Evidence of Past Abuse Under G.L. c. 233, § 23F

A defendant who raises self-defense may offer evidence that the defendant has been the victim of physical, sexual, or psychological abuse, including duress. G.L. c. 233, § 23F. This defense is not limited to women, but was popularly referred to as battered woman syndrome. The defendant may also offer expert testimony about the common pattern in abusive relationships and the effects of abuse on the fight-or-flight response of a person who has been formerly abused. Id.

The jury may consider the evidence of past abuse and the expert testimony to answer three questions. First, did the defendant reasonably fear imminent death or serious bodily injury. Second question did the defendant reasonably believe that they had tried every means of avoiding physical combat. Third question, did the defendant reasonably assess and use only the reasonably necessary amount of force. Id.

Former abuse evidence in self-defense is not limited to abuse from the alleged victim in the new case. Commonwealth v. Anestal, 463 Mass. 655, 675-676 (2012). Abuse from any other person can be relevant to the fight or flight response in self-defense. Also, a defendant does not have to present evidence of prior abuse before offering expert testimony about the effects of duress or fear of abuse in self-defense under § 23F. Commonwealth v. Asenjo, 477 Mass. 599, 605-606 (2017).

The Alleged Victim’s History of Violence

Evidence of an alleged victim’s past violence can help show who more likely started the fight currently on trial. When the parties dispute who started the fight, the judge may admit evidence of specific violent acts that the alleged victim has engaged in previously, even if the defendant did not know about those acts. Commonwealth v. Adjutant, 443 Mass. 649, 654-655, 664 (2005). The same rule applies when the dispute is about who first used or threatened deadly force. Commonwealth v. Chambers, 465 Mass. 520, 529-530 (2013).

Separately, an alleged victim’s violent acts that the defendant knew about can be admitted to show the defendant’s state of mind. Commonwealth v. Fontes, 396 Mass. 733, 735-736 (1986). This evidence is important to show that the defendant knew that the alleged victim had the propensity to be violent, and that they need to use force to avoid what they feared would be new violence.

The defense must give the prosecutor written notice of first-aggressor evidence no later than 21 days after the pretrial hearing, unless the judge sets another time for good cause. Mass. R. Crim. P. 14.3(c)(1). When the defense offers that evidence, the Commonwealth may answer with its own specific violent acts of the defendant. Commonwealth v. Morales, 464 Mass. 302, 309-310 (2013). The firm’s page on Adjutant evidence and prosecution rebuttal explains the notice, the judge’s balancing test, and the limiting instruction.

Defense of Another Person

A person may also use reasonable force to protect another person, such as a child in the home. The force is justified when a reasonable person in the defendant’s position would believe that intervening was necessary to protect the other person. The same preliminary standard of self-defense applies here. The third-party that the defendant protected must have been entitled to use the same force in self-defense to justify the defendant’s use of force. Commonwealth v. Martin, 369 Mass. 640, 649 (1976). District Court Model Jury Instruction 9.264 (rev. Oct. 2024).

Evidence That Shows Who Started the Fight

The jury’s decision on self-defense usually depends on the sequence of events. A 911 recording can show who called for help, what each person said and did before the police arrived, and whether either account changed afterwards. Body camera video can show each person’s injuries, demeanor, and statements close in time to the incident, along with the layout and any damage or disarray in the room where the fight happened.

Photographs of injuries taken promptly and from more than one angle can show whether a person received an injury while attacking or while defending. Scratches on the forearms, for example, can show that a person was blocking blows. Medical records can also help to show whether a person received an injury while attacking or while defending themselves.

Text messages and other messages sent before and after the incident can also show who was initially aggressive or angry and who tried to placate or leave the situation. Defense counsel should always obtain and preserve a complete message thread rather than single screenshots, so that the jury sees every message sent before and after the incident in its proper context.

Contact With the Alleged Victim While the Case Is Pending

A defendant should not discuss a pending case with the alleged victim. At arraignment, the judge often orders the defendant, as a condition of release, to have no contact with the alleged victim. A defendant who has contact with the alleged victim can also violate a 209A restraining order, even if the alleged victim initiated the contact. The firm’s pages on no contact orders as conditions of release and intimidation of a witness explain the consequences of contact.

Preparing a Domestic Self-Defense Case

Attorney Serpa obtains the 911 recording, the body camera video, the booking photographs, and the police reports early in the case. He documents the client’s injuries and collects the messages from before and after the incident. He investigates any prior violence by the alleged victim before deciding whether to give notice of first-aggressor evidence, because if the defense offers that evidence at trial, the Commonwealth may answer with specific violent acts of the client.

A person charged with domestic assault who acted in self-defense should speak with a lawyer before saying anything to the police or to the alleged victim. Request a consultation before the arraignment or the next court date.

Frequently Asked Questions

Related Serpa Law Office Resources

• Self-Defense in Massachusetts
• Adjutant Evidence and Rebuttal in Massachusetts Self-Defense Cases
• Assault and Battery on a Family or Household Member
• Falsely Accused of Domestic Violence in Massachusetts
• When the Alleged Victim Will Not Testify in a Massachusetts Domestic Violence Case
• No Contact Orders in Massachusetts Criminal Cases
• Strangulation or Suffocation in Massachusetts
• Assault and Battery with a Dangerous Weapon
• Boston Domestic Violence Defense Lawyer