Assault with a weapon is defined in MCA § 45-5-213. Like aggravated assault, it is a general statute that says nothing about partners or family members, but it is one of the charges prosecutors use when a domestic incident involved an object the State calls a weapon. It carries up to 20 years in the state prison. This page covers the elements, the code's definition of a weapon, and what changes when the other person is a partner or family member. It is part of our Montana Domestic Violence Guide.
The Elements
A person commits assault with a weapon by purposely or knowingly causing either of two things (MCA § 45-5-213(1)):
- bodily injury to another with a weapon, or
- reasonable apprehension of serious bodily injury in another by use of a weapon or what reasonably appears to be a weapon.
Notice the difference between the two. With actual injury, ordinary bodily injury is enough, which the code defines to include physical pain (MCA § 45-2-101). With apprehension alone, the fear must be of serious bodily injury. Those terms are explained in what bodily injury means and in our page on aggravated assault on a partner.
What Counts as a Weapon
The definition is in MCA § 45-2-101: a weapon is "an instrument, article, or substance that, regardless of its primary function, is readily capable of being used to produce death or serious bodily injury."
Three things follow from that wording. The definition is not limited to firearms and knives. An object's ordinary purpose does not settle the question, because the statute says "regardless of its primary function." And the test is capability: whether the thing is readily capable of producing death or serious bodily injury. Whether a particular object meets that test in a particular case is decided on the evidence, including how the State says it was used.
The second version of the offense reaches further, to "what reasonably appears to be a weapon."
Weapon Allegations Under PFMA and Under § 45-5-213
The PFMA statute has its own weapon clause, and the mental state is what separates the two.
| What the State alleges | Offense | Penalty in the statute |
|---|---|---|
| Purposely or knowingly causes bodily injury with a weapon | Assault with a weapon, § 45-5-213(1)(a) | State prison up to 20 years, a fine up to $50,000, or both |
| Purposely or knowingly causes reasonable apprehension of serious bodily injury by use of a weapon, or what reasonably appears to be one | Assault with a weapon, § 45-5-213(1)(b) | State prison up to 20 years, a fine up to $50,000, or both |
| Negligently causes bodily injury to a partner or family member with a weapon | PFMA, § 45-5-206(1)(b) | First offense: 24 hours to 1 year in county jail and a fine of $100 to $1,000 |
| Purposely or knowingly causes reasonable apprehension of bodily injury in a partner or family member, no weapon alleged | PFMA, § 45-5-206(1)(c) | First offense: 24 hours to 1 year in county jail and a fine of $100 to $1,000 |
See purposely, knowingly, and negligently for how Montana defines each mental state.
The Penalty
A person convicted of assault with a weapon "shall be imprisoned in the state prison for a term not to exceed 20 years or be fined not more than $50,000, or both" (MCA § 45-5-213(2)(a)). The statute sets no minimum term.
If the person convicted is a partner or family member of the victim, the court must also require the person to pay for and complete the counseling assessment described in the PFMA statute (MCA § 45-5-213(2)(b)). Our PFMA counseling requirement page explains what that involves.
When the Other Person Is a Partner or Family Member
- No contact order. MCA § 45-5-209 applies to a § 45-5-213 charge when the alleged victim is a partner or family member. An order can be served at arrest, lasts 72 hours or until the first appearance, and can be continued or reissued by the court.
- PFMA priors. A conviction counts toward the number of prior convictions if a PFMA is ever sentenced later (MCA § 45-5-206(3)(b)(iv)).
- Children present. An added charge of endangering the welfare of children is possible under MCA § 45-5-622(4).
Firearms and a Pending or Past Charge
Federal law prohibits firearm and ammunition possession by a person convicted of a crime punishable by imprisonment for more than one year (18 U.S.C. § 922(g)(1)). Assault with a weapon is such a crime. Release conditions and court orders may restrict firearms much earlier, while the case is still pending. If any order or condition restricts firearms, follow it exactly. Our pages on firearms while the case is pending and felony convictions and firearms go into detail.
A&M Law defends these charges in Western Montana. See our assault 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.