In self-defense law, the term “third party” comes up often — but what does it actually mean, and how does it apply when force or deadly force is used?
Whether you’re a CCW holder, security guard, or armed citizen, it’s important to understand that using force to defend yourself is not the same as using force to defend someone else. The law treats those situations very differently, and the stakes are high when you decide to step in to protect another person.
In this article, we break down what “third party” means under Colorado Revised Statutes (CRS), how it fits into lawful use of force, and when it can — and cannot — justify your actions in a violent encounter.
What Does “Third Party” Mean?
In simple terms, a third party is any person other than yourself.
Under self-defense laws, if you’re intervening to protect someone else from being harmed — whether it’s a friend, family member, coworker, or even a complete stranger — you are engaging in what’s legally referred to as defense of a third party.
You’re not defending your own body or property. You’re stepping in on someone else’s behalf. And when you do, the law holds you to a very specific standard.
Colorado Law: CRS § 18-1-705 – Use of Force in Defense of a Third Person
Colorado law allows you to defend a third party, but only under specific conditions.
CRS § 18-1-705 states:
“A person is justified in using physical force upon another person in order to defend a third person from what he or she reasonably believes to be the use or imminent use of unlawful physical force by such other person, and he or she may use a degree of force which he or she reasonably believes to be necessary for that purpose.”
But there’s a catch:
“A person is justified in using deadly physical force only if the person defended would have been justified in using such deadly physical force.”
In Plain English:
You step into the shoes of the person you’re defending. If they would have had the legal right to use force or deadly force — then you may be justified in using it on their behalf.
But if they weren’t legally justified (for example, they were the initial aggressor or provoked the fight), then you aren’t justified either.
Why It Matters
This concept is crucial for armed citizens and professionals. If you decide to intervene to protect a third party, you’re not just risking your life — you’re also taking on the legal consequences of their actions. You don’t get to use force based on how you feel — it’s based on what the person you’re defending was legally entitled to do.
Real-World Examples
✅ Lawful Third-Party Defense:
A man is assaulting a woman in a parking lot — punching her, trying to drag her toward a vehicle. She’s screaming and trying to escape. Based on your observations, you reasonably believe she’s the victim of a kidnapping or assault.
In this case, she would likely be justified in using deadly force to stop the attack. Because of that, you could be justified in using deadly force to defend her under CRS § 18-1-705.
❌ Unlawful Third-Party Defense:
You walk into a bar and see two men fighting — one of them is your friend. Without asking questions, you pull your firearm and threaten the other person to “protect” your buddy.
But what if your friend started the fight? What if he threw the first punch? If he wasn’t legally justified in using force, you have no legal standing to defend him. You could be criminally charged or sued in civil court for your actions.
Mutual Combat and Provocation
Two key things that disqualify a person from lawful self-defense (and therefore disqualify you from third-party defense):
- Mutual Combat – If both parties willingly engage in a fight, they generally lose the legal protection of self-defense.
- Provocation – If the person you’re defending started the confrontation or provoked the attack, they may not have a legal right to use force — and neither do you.
Reasonable Belief Still Matters
CRS § 18-1-705 uses the phrase “reasonably believes”, meaning your belief that the third party was under threat doesn’t have to be perfect — but it does have to be reasonable to an average person under the same circumstances.
This means acting on limited or wrong information can still get you into legal trouble if your belief wasn’t reasonable in the eyes of the law.
Conclusion: Know Who You’re Defending
Using force to defend a third party can be justified — but it’s a legal minefield if you don’t understand the rules. Before intervening, ask yourself:
- Would the person I’m helping be legally justified in using force?
- Am I reasonably sure they’re not the initial aggressor?
- Do I fully understand the situation — or am I jumping in blind?
The bottom line: a third party is anyone other than you. But defending them legally means accepting the full legal responsibility for what happens next.
Learn More About the Law
Our certified CCW and armed security classes cover third-party defense, Colorado Revised Statutes, and real-world scenarios in detail. We prepare our students not just to shoot — but to think critically under pressure.
This article is for informational purposes only and does not constitute legal advice. Always consult a qualified attorney regarding self-defense laws in your state. Concealed Carry Classes of Denver LLC is not a law firm and does not offer legal services.
