Montana Domestic Violence Guide

The Six Predominant Aggressor Factors in Montana

When both people appear to have used force, Montana law tells the officer to work out who the predominant aggressor is. Here is each consideration.

Written by

Ashley Hurlbert, Partner, A&M Law

Licensed Montana attorney and co-founder of A&M Law. 18 years of experience as lead counsel in 50+ jury and bench trials. A Certified Mediator and Certified Guardian ad Litem focusing on family law, criminal defense, and DUI defense.

18 yearsReviewed by Misty GaubatzLast reviewed: September 2, 2026

Key Takeaways: The Six Predominant Aggressor Factors in Montana

The predominant aggressor review applies when an officer responds to a PFMA complaint and it appears the parties were involved in mutual aggression (MCA § 46-6-311(2)(b)).
The officer must evaluate who the predominant aggressor is. If the officer determines that one person is, the officer may arrest only that person.
The six considerations apply regardless of who was the first aggressor. Who started it does not decide the question.
The list is not exclusive. The determination must be based on the six considerations but is not limited to them.
Self-defense is one of the six, so an officer is supposed to consider it at the scene.
The officer's determination is an arrest decision. It is not a finding of guilt, and a court is not bound by it.

When Montana officers arrive at a domestic call and find that both people appear to have used force, they are not supposed to simply arrest whoever admits to a push, or arrest both. The statute requires an evaluation of who the predominant aggressor is, and it lists six considerations for making that call. This page takes them one at a time. It is part of our Montana Domestic Violence Guide.

The Text of the Rule

MCA § 46-6-311(2)(b) reads, in relevant part: when a peace officer responds to a partner or family member assault complaint "and if it appears that the parties were involved in mutual aggression, the officer shall evaluate the situation to determine who is the predominant aggressor. If, based on the officer's evaluation, the officer determines that one person is the predominant aggressor, the officer may arrest only the predominant aggressor."

Three things about that text are worth noticing. The evaluation is required ("shall"). The list that follows is a floor, because the determination "must be based on but is not limited to" the six considerations. And all of it applies "regardless of who was the first aggressor."

The Six Considerations

§ 46-6-311(2)(b)	Consideration in the statute	Kinds of information that bear on it
(i)	Prior history of violence between the partners or family members, if that information is available to the officer	Earlier calls to the address, prior charges, existing orders, and what each person says about the past
(ii)	Relative severity of injuries received by each person	Photographs, descriptions of marks, complaints of pain, medical attention
(iii)	Whether an act of or threat of violence was taken in self-defense	Each person's account of who did what and why, and whether injuries fit that account
(iv)	Relative sizes and apparent strength of each person	The officer's own observations of each person
(v)	Apparent fear or lack of fear between the partners or family members	Demeanor, as the officer describes it
(vi)	Statements made by witnesses	Children, neighbors, relatives, the 911 caller

The middle column is the statute. The right column is our description of the kinds of information that relate to each one. It is not a statutory checklist.

History, Injuries, and Self-Defense

Prior history of violence.The statute adds a condition: "if information about the prior history is available to the officer." An officer on a doorstep at night may know only what dispatch relays and what the two people say. History can point either way, and it can be incomplete.

Relative severity of injuries. The comparison is between the injuries "received by each person." An injury may not be visible in the first hour, and a visible mark can be defensive. A scratch on one person and a complaint of throat pain from the other are not weighed by counting marks. Our page on photos and medical records covers how injuries are documented.

Self-defense. Montana law justifies the use of force when and to the extent a person reasonably believes it is necessary to defend against another's imminent use of unlawful force (MCA § 45-3-102). The arrest statute makes the officer consider that at the scene. A separate statute says that when an incident appears or is alleged to have involved justifiable use of force, the investigation "must be conducted so as to disclose all evidence," including evidence that might support the justification (MCA § 45-3-112). See self-defense in a PFMA case.

Size, Fear, and Witnesses

Relative sizes and apparent strength.This is an observation, and the word "apparent" signals that it is the officer's impression. It is one consideration, not a presumption against the larger person.

Apparent fear or lack of fear.Again the word is "apparent." People show fear differently. Some go quiet, some are angry, and alcohol changes how anyone presents. An officer's reading of demeanor is recorded in the report as the officer saw it, and body camera footage, where it exists, lets others look at the same moments.

Statements made by witnesses. The statute does not limit who counts. Children in the home can be witnesses, which raises its own concerns, covered in children as witnesses. If you know of a witness, give the name to your lawyer. Do not contact witnesses yourself, and never contact a person protected by a no contact order.

How the Determination Shows Up on Paper

Montana law requires two documents that bear on this. A charge of PFMA "must be supported by a peace officer's affidavit of probable cause" (MCA § 45-5-209(3)). And when an officer responds to a reported incident of domestic violence and does not arrest, the officer must file a written report giving the reasons (MCA § 46-6-601).

Neither statute prescribes a form for the six considerations. A report may address each one in order or cover them in a narrative, and it may say a great deal about one consideration and nothing about another. When your lawyer receives the reports, recordings, and photographs through discovery, comparing them against the statutory list is a basic step: which considerations were addressed, what each conclusion rested on, and what the recordings show.

What the Determination Does and Does Not Decide

It decides who may be arrested at the scene. It does not decide the charge, which is the prosecutor's job, and it does not decide guilt. At trial the State must prove the elements of PFMA beyond a reasonable doubt, and when the defendant has offered evidence of justifiable use of force, the State has the burden of proving beyond a reasonable doubt that the defendant's actions were not justified (MCA § 46-16-131).

The statute also leaves a gap. It says what the officer may do after determining that one person is the predominant aggressor. It does not say what happens when the officer cannot tell. That is one way both people end up arrested. And if you were the one who called for help, see if you called the police and got arrested.

If you are in danger, call 911. The National Domestic Violence Hotline is 1-800-799-7233. For how A&M Law defends these charges, see our PFMA defense page.

This page explains Montana law in general as of the 2025 Montana Code Annotated. It is not legal advice about your specific case.

Montana Domestic Violence Guide Domestic Violence Defense Talking to Police at the Scene Police Entering Your Home Weapons Seized at the Scene The 911 Call as Evidence

FAQ

The Six Predominant Aggressor Factors in Montana FAQ

What does predominant aggressor mean in Montana?

The statute does not define the phrase. It tells the officer how to decide: by weighing six listed considerations, among others, "regardless of who was the first aggressor" (MCA § 46-6-311(2)(b)). In plain terms it asks who was the main source of the violence, not who touched whom first.

Does it matter who started the fight?

Not by itself. The statute says the determination is made "regardless of who was the first aggressor." Who acted first can still be relevant to the third consideration, whether an act or threat of violence was taken in self-defense.

I am bigger than my partner. Does that mean I get arrested?

Relative size and apparent strength is one consideration out of six, and the statute does not rank them. An officer is also required to consider injuries to each person, self-defense, prior history, apparent fear, and witness statements. How an officer weighed them in your case is a question to go over with your lawyer once the reports arrive.

Can I challenge the officer's predominant aggressor decision?

There is no separate hearing on that decision in the statute. What you can challenge is the case: whether there was probable cause, and whether the State can prove PFMA beyond a reasonable doubt and disprove self-defense if you raise it. The facts behind the six considerations are often the same facts that matter at trial.

Where do I see how the officer applied the factors?

In the officer's affidavit of probable cause, which must support the charge (MCA § 45-5-209(3)), and in the reports and recordings your lawyer requests from the prosecutor under MCA § 46-15-322. See discovery in a PFMA case.

Think the Officer Got It Wrong?

We compare the report to the six factors the statute requires. Call 406-830-3060 for a confidential consultation.

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