Missouri First-Degree Murder

Created by FindLaw's team of legal writers and editors | Last reviewed June 20, 2016

First degree murder is the most serious of the homicide crimes in Missouri. In order to prove that the defendant committed first degree murder, the prosecutor must show beyond a reasonable doubt that the defendant intentionally and deliberately killed a person without a legally justified reason (such as a police officer shooting an armed bank robber with hostages). Serial murderers who kill for fun and individuals who plot and execute a revenge killing of someone who allegedly slighted them would both be examples of first-degree murder.

Missouri first degree murder laws treat the offense as a very serious crime. The penalties are based on the circumstances of the crime. If the criteria for first degree murder isn't met, the defendant may still be found guilty of a lesser murder charge, such as: second degree murder (killing without premeditation), voluntary manslaughter ("heat of passion murder"), or involuntary manslaughter (an accidental killing).

Defenses to Murder Charges

Some defenses to first degree murder are complete, meaning the person walks free if believed by the court. For example, innocence is a complete defense, as potentially lack of intent or lack of knowledge could be. However, others defenses, such as self-defense, insanity, or intoxication are often only partial. Partial defenses may only reduce the crime to a lower murder charge, such as manslaughter.

Penalties and Sentences

Missouri law permits capital punishment, or the death penalty. A capital murder case is bifurcated. First, the issue of guilt is determined. Then a second phase of the trial on sentencing begins. At the sentencing hearing, the judge or jury hears evidence on both aggravating and mitigating factors involved in the crime and issues a penalty, including death, based on those factors. Aggravating circumstances show maliciousness, insult, lack of remorse, etc. and increase penalties, while mitigating circumstances decrease criminal responsibility or bear on why the crime was committed (such as years of abuse at hands of the murder victim), thereby making a less severe sentence reasonable.

Missouri law dictates what can be considered as aggravating and mitigating factors. The aggravating factors that can be presented by the prosecutor are:

The murder was committed:
- In an outrageous, vile, or depraved manner or involved torture
- While committing or attempting another homicide
- While creating a significant risk of death to more than one person because of the weapon or device used (i.e. a bomb)
- For money (i.e. paid hitman or kills spouse for life insurance funds)
- While committing or attempting rape, sodomy, burglary, robbery, kidnapping, or a felony drug offense
- To conceal a drug-related felony offense
- To avoid arrest
- To stop a person from aiding in a drug felony offense prosecution
- During the commission of a "criminal street gang activity" crime
The victim was:
- A judge, prosecutor, peace officer, or elected official
- A police officer or fireman in the line of duty
- A corrections employee or an inmate
- Killed because he or she witness in an investigation or prosecution
- Killed due to a hijacking
The defendant:
- Had prior murder or serious assault convictions
- Directed another to commit the murder or committed murder for another
- Was escaping jail or prison when he or she killed the victim

The mitigating circumstances that can be considered are:

That the defendant:
- Has no significant history of prior criminal activity
- Was a minor accomplice to a murder committed by another
- Acted under extreme duress or under the control of another
- Lacked the capacity to appreciate his or her conduct and the law
- Was young at the time of the crime
- Was under extreme mental or emotional disturbance
That the victim:
- Consented or participated in the defendant's act