Missouri First Degree Murder Lawyers

Quick Reference for RSMo 565.020

Element	Details
Classification	Class A felony (Missouri’s most serious homicide offense)
Sentence (offender 18 or older)	Death or life imprisonment without eligibility for probation, parole, or release except by act of the governor
Sentence (offender under 18)	Governed by § 565.033, RSMo
Distinguishing element	Deliberation, meaning cool reflection for any length of time
Death-penalty eligibility	Requires at least one statutory aggravating circumstance under § 565.032, RSMo
Penalty procedure	Bifurcated: separate guilt phase and penalty phase in capital cases
Offender status	No Three-Strikes analog; capital scheme applies, not § 558.016 ranges
Statute of limitations	None

What first degree murder means under Missouri law

First degree murder is knowingly causing the death of another person after deliberation upon the matter. That one added word, deliberation, is what makes this the most serious homicide charge Missouri recognizes.

“A person commits the offense of murder in the first degree if he or she knowingly causes the death of another person after deliberation upon the matter. The offense of murder in the first degree is a class A felony, and, if a person is eighteen years of age or older at the time of the offense, the punishment shall be either death or imprisonment for life without eligibility for probation or parole, or release except by act of the governor.”¹

In plain terms, the State must show two mental states, not one. You knowingly caused the death, meaning you were aware your conduct was practically certain to kill, and you acted after deliberation, meaning you reflected on it coolly before you acted.

Second degree murder involves the same death and the same knowing mental state. It simply lacks deliberation.² That is the entire dividing line. A killing that is knowing but impulsive, or done in sudden passion, is not first degree murder no matter how tragic the result.

What the prosecution has to prove

To convict you of first degree murder, the State must prove each of the following beyond a reasonable doubt.³ If it cannot prove even one, the charge fails.

You caused the death by the means used. The State must connect your conduct to the death itself. This is the causation element, and it is not automatic. Where a medical complication, a third party, or an intervening event contributed to the death, the chain the State needs can break. Causation is contested more often than people expect.

You acted knowingly, or with the purpose to cause death. The State must prove you knew your conduct was causing or was practically certain to cause death, or that causing death was your actual purpose. Recklessness or negligence does not satisfy this element. A death caused by carelessness, however serious, is a different offense entirely.

You acted after deliberation. Deliberation means cool reflection upon the matter for any length of time, no matter how brief. It does not require planning over days. But it does require reflection, not reaction. A killing born of sudden anger, provocation, or panic is by definition not deliberate. This is the element that carries the whole charge.

You were eighteen or older at the time of the offense. Age determines the sentencing scheme. An offender who had not reached eighteen at the time of the offense is sentenced under § 565.033, RSMo, not the adult death or life-without-parole terms.⁴

Each element is a separate question the State has to answer, and each one is a place the defense goes to work. Where deliberation is thin, the offense drops. That is where the contest usually begins.

Deliberation and the line between first and second degree

Here is what most people misunderstand about this charge. They assume “premeditation” means a long plan, weeks of scheming, a diagram on a wall. Missouri law asks far less. Deliberation can form in a moment, so long as it was cool reflection rather than a reaction in the grip of passion.

But that low bar cuts both ways. Because deliberation can be brief, the State often tries to infer it from the circumstances, the number of wounds, the choice of weapon, a pause between acts. Inference is not proof. When the evidence shows a killing that erupted suddenly, that followed provocation, or that happened in a haze of intoxication or fear, the deliberation theory weakens.

This is the reframe that matters in these cases. The question is rarely whether someone died. It is what the State can prove about your state of mind in the seconds or minutes that led to the death. Sudden passion from adequate cause points toward voluntary manslaughter. A knowing but impulsive act points toward second degree murder. Reflection is what the State needs, and reflection is what it most often cannot prove.

We have seen prosecutors commit early to a deliberation narrative built on inference, then struggle when the timeline and the physical evidence tell a different story. That version has gaps. Finding them is the work.

Degrees of homicide and related charges

First degree murder sits at the top of a ladder of Missouri homicide offenses, each defined by a different mental state.

Murder in the second degree (§ 565.021, RSMo). A knowing killing without deliberation, or a death caused during the commission of a felony (felony murder). This is the most common step-down from a first degree charge when deliberation cannot be proven.²

Voluntary manslaughter (§ 565.023, RSMo). A knowing killing committed under the influence of sudden passion arising from adequate cause. When provocation is real and the reaction immediate, this offense recognizes that the killing, while unlawful, was not the product of cool reflection.⁵

Involuntary manslaughter (§ 565.024, RSMo). A reckless killing. The mental state is lower still, and the offense reflects conduct that caused death without the awareness first and second degree require.⁶

First degree murder cases also frequently carry co-charges. Armed criminal action (§ 571.015, RSMo) is common where a deadly weapon was used.⁷ Robbery, burglary, or kidnapping may appear as predicate felonies supporting a felony-murder theory or a death-penalty aggravator.

Penalties and what a conviction means

For an offender eighteen or older at the time of the offense, first degree murder carries only two possible sentences on conviction.

Circumstance	Sentence
Offender 18 or older	Death, or life imprisonment without eligibility for probation, parole, or release except by act of the governor¹
Offender under 18	Punishment as provided under § 565.033, RSMo⁴

There is no term of years. There is no parole. Life without parole means exactly that. The only path out is an act of the governor, which is not a sentencing option a court weighs.

First degree murder is a Class A felony, but it does not follow the ordinary Class A imprisonment ranges of § 558.011, RSMo. It carries its own dedicated capital sentencing scheme.

Death-penalty eligibility is not automatic. It requires the State to prove at least one statutory aggravating circumstance under § 565.032, RSMo, litigated in a separate penalty phase.⁸ Missouri capital cases are bifurcated: a guilt phase decides whether the offense occurred, and a separate penalty phase weighs aggravating against mitigating circumstances (§ 565.030, RSMo).⁹

Missouri has no Three-Strikes analog. This charge is governed by its own scheme, not the prior, persistent, or dangerous-offender ranges of § 558.016, RSMo. There is also no statute of limitations on first degree murder; the State can bring the charge at any time.

For a charge with only these outcomes, prison is the consequence. Collateral effects on employment or licensing are beside the point. What the penalty phase decides is whether the outcome is death or life.

How these cases are defended

A first degree murder defense is built on two tracks at once: contesting the charge itself, and preparing for the penalty phase in case the guilt phase does not end the matter. Both begin immediately.

Attack deliberation. This is the defense that changes the charge. If the State cannot prove cool reflection, first degree murder is not the offense. Evidence of sudden passion, provocation, intoxication, or an impulsive act undermines deliberation and can move the case toward second degree murder or voluntary manslaughter. A killing that followed a heated confrontation, with no pause for reflection, is a different charge than the one the State filed.

Challenge the mental state. The State must prove you knew death was practically certain or acted with the purpose to kill. Where the facts show recklessness or a tragic accident rather than a knowing act, the required mental state is absent, and a lesser homicide offense fits the facts.

Self-defense or defense of others. Justification is a complete defense. Missouri law permits deadly force where a person reasonably believes it necessary to protect against death, serious physical injury, or certain forcible felonies (§ 563.031, RSMo).¹⁰ A death that occurred while lawfully defending yourself or another is not murder at all. Consider a person cornered in their own home by an armed intruder: the law does not require them to wait to be harmed first.

Contest identity and reconstruct the timeline. The State has to prove you were the person who caused the death. DNA, eyewitness reliability, surveillance timelines, and evidence of third-party culpability all come into play. Eyewitness identification, in particular, is far less reliable than juries assume.

Diminished capacity and mental disease or defect. Evidence of mental illness can negate the deliberation or knowing element, or support a defense of not guilty by reason of mental disease or defect under Chapter 552, RSMo.¹¹ Mental state is the heart of this charge, and mental health evidence goes directly to it.

Suppress unlawfully obtained evidence. Confessions taken in violation of Miranda, searches that breached the Fourth Amendment, and suggestive identification procedures can all be challenged. In a capital case, a single successful suppression motion can be dispositive.

Contest causation. Where an intervening cause, a medical complication or a third party’s conduct, contributed to the death, the State’s claim that your conduct caused it can be challenged directly.

Prepare penalty-phase mitigation. In a death-eligible case, a thorough mitigation investigation into mental health, trauma history, and background is not optional. It is often what secures life instead of death when the guilt phase ends unfavorably.

Where a St. Louis case is heard

First degree murder cases in the region are prosecuted through the circuit court’s felony division. St. Louis County cases proceed through the 21st Judicial Circuit in Clayton; cases arising in the City of St. Louis, a separate jurisdiction, proceed through the 22nd Judicial Circuit. Capital cases carry additional pretrial procedures, including the State’s notice of intent to seek death and the appointment of qualified capital counsel.

We defend homicide cases in both jurisdictions and know how these charges are actually built and tried here. That knowledge shapes the defense from the first interview forward.

Charged with first degree murder in St. Louis?

This is the most serious charge Missouri brings, and the defense should start now, while witnesses remember clearly and physical evidence can still be independently examined. The State committed to its version of events early. That version has gaps, and the earliest defense is the strongest one.

We build the case immediately, on both the guilt and penalty tracks, and hold the State to its burden at every stage. If you or a family member is facing a first degree murder charge, the next step is a direct conversation about the facts and the options.

Talk to our St. Louis homicide defense team.

References

1. § 565.020, RSMo [“A person commits the offense of murder in the first degree if he or she knowingly causes the death of another person after deliberation upon the matter… the punishment shall be either death or imprisonment for life without eligibility for probation or parole, or release except by act of the governor.”]

2. § 565.021, RSMo (murder in the second degree; knowing killing without deliberation, and felony murder).

3. MAI-CR 4th 414.02 (pattern jury instruction for murder in the first degree).

4. § 565.033, RSMo (sentencing for offenders under eighteen at the time of the offense; cf. § 558.047, RSMo; Miller v. Alabama, 567 U.S. 460 (2012)).

5. § 565.023, RSMo (voluntary manslaughter; knowing killing under sudden passion arising from adequate cause).

6. § 565.024, RSMo (involuntary manslaughter; reckless killing).

7. § 571.015, RSMo (armed criminal action).

8. § 565.032, RSMo (statutory aggravating circumstances required for death-penalty eligibility).

9. § 565.030, RSMo (bifurcated trial procedure; separate guilt and penalty phases in capital cases).

10. § 563.031, RSMo (use of force in defense of persons).

11. Chapter 552, RSMo (mental disease or defect excluding responsibility; diminished capacity).