Although states vary in their definitions, the majority of states define homicide is the unlawful killing of a human being. Killing a person in self-defense is a lawful killing of another person. Therefore, it is not a homicide.
There are four degrees of homicide which vary according to the actor’s state of mind when he or she commits an act that causes the death of another person. The four degrees of homicide are:
1. Murder in the First Degree (premeditated intent to kill another person). Note that premeditation is defined as forming the specific intent to kill before committing the act that causes the death of another person. There is no established minimum amount of time, but the actor must have had an opportunity to reflect on the decision to kill before committing the act that causes death.
2. Murder in the Second Degree (intentional murder). In effect, the actor forms the specific intent to kill another person and acts immediately such that the formation of intent and the act occur simultaneously or so close together that there is no opportunity to reflect on the decision. Murder in the Second Degree typically involves killing another person in the heat of passion.
3. Manslaughter in the First Degree (reckless killing). The actor engages in conduct knowing that there is a substantial risk that the conduct will cause the death of another person. The typical example is playing Russian Roulette with another person. There is no intent to kill, but a death results nevertheless.
4. Manslaughter in the Second Degree (criminally negligent killing). The actor causes the death of another person while committing an act that he should have known would likely cause the death of another person and his failure to know that constitutes a gross deviation from the standard to act with due care to avoid injuring others.
Depending on whether a state has the death penalty, there is another category called Aggravated Murder, which is a premeditated murder with aggravating circumstances.
Aggravating circumstances are defined by statute and typically include the premeditated killing of another person to conceal the commission of another crime. For example, a rapist kills the victim to prevent her from reporting the crime and identifying him. Other examples include the premeditated murder of a cop or a judge. In each case the aggravating circumstance is the purpose behind the premeditated intent to kill.
The death penalty is not automatically imposed upon conviction of aggravated murder, no matter how heinous or depraved. Instead, a sentencing hearing is held after the jury convicts the defendant of aggravated murder in which the same jury that convicted him considers evidence submitted by the prosecution in aggravation of the offense and evidence offered by the defense in mitigation of the offense.
Evidence in aggravation includes the evidence the jury already heard about the offense in the guilt phase, a statement from a friend of the victim or member of the victim’s family who testifies regarding the impact of the victim’s death on the witness or family, and evidence of the defendant’s prior record of criminal convictions, if any exists.
Evidence in mitigation is evidence about the defendant, such as organic brain disorder, limited intellectual functioning, mental illness, victim of childhood sexual abuse or assault, or the defendant’s role in committing the murder (e.g., an accomplice who assisted another person to commit the murder but who did not commit the murder and may not have even been present when it occurred) that in fairness or mercy warrants a sentence of life without possibility of parole instead of the death penalty.
In Washington State where I handled all of my death penalty cases, the final instruction given to the jury after both sides rest in the penalty phase is as follows:
Having in mind the crime of which the defendant has been convicted, are you convinced beyond a reasonable doubt that there are not sufficient mitigating circumstances to merit a sentence of less than death?
The jury also is instructed that the law presumes that the appropriate sentence is life without possibility of parole unless the prosecution overcomes that presumption with proof beyond a reasonable doubt that there are not sufficient mitigating circumstances to merit the life without parole sentence.
The jury must be unanimous to impose the death sentence.