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Matthew A. Radefeld and Daniel A. Juengel

Voluntary manslaughter defenses in St. Louis, MO

On Behalf of | Feb 8, 2022 | Homicide |

Voluntary manslaughter is when an individual deliberately kills another because of anger or passion. The killing must have happened before the perpetrator had time to “calm down” or “cool off.” If there was no emotional excitement that caused anger, the killing is defined as a murder instead. Missouri law also recognizes knowingly helping another person cause “self-murder” as voluntary manslaughter (better known in other jurisdictions as “assisted suicide”).

In Missouri, voluntary manslaughter is classified as a Class B felony, and the penalty includes 5-15 years in prison and a fine of up to $5,000. However, a person charged with manslaughter has a right to defend themselves or justify their actions. Below are some effective defenses against a voluntary manslaughter charge.

Actual innocence

The prosecutors have the burden of proving that the defendant committed the crime and is guilty beyond a reasonable doubt. In their defense, the defendant may prove that the evidence against them is not valid or could claim an alibi. The jury may return an acquittal if the defendant provides a reasonable doubt about their guilt.


For the court to consider the killing was a result of self-defense, the defendant must show that there was a reasonable need for deadly force to protect their life or the life of someone else.

Accidental killing

Proving that the homicide was the result of an accident is another valid defense against voluntary manslaughter charges. This claim also has the potential to reduce the charge to involuntary manslaughter, which is caused by negligent or reckless behavior. The defendant carries the burden of showing that the victim’s death did not result from an intentional act.

Involuntary intoxication

Intoxication is not a valid excuse for criminal behavior unless the defendant was drugged against their will. A successful intoxication defense may cause the court to reduce the charge to involuntary manslaughter or drop it altogether.


A defendant may choose to defend themselves by proving or showing that they lacked the mental capacity to commit voluntary manslaughter. However, if the defendant is found not guilty because of insanity, the court may send them to a mental health institution for treatment if they are considered a danger to the community.

Some states do not explicitly allow for an insanity defense, but Missouri does. The insanity defense is outlined by the M’Naghten Rule. Under this statute, the court can determine that a suspect did not understand what they were doing because of a “disease of their mind.”