Homicide is one human being causing the death of another. However, determining whether a human being has been killed is not as straightforward as it seems. The definition of “human being” varies by jurisdiction. Some require being born alive in order to be considered a human being, while others permit fetuses in gestation to be considered a human being. The definition of “death” also varies by jurisdiction. Death may be complete cessation of respiratory function, or cardiac function, or brain activity, or some combination of these. Therefore what sounds like a simple definition is actually quite complicated under the law. It requires establishing that a homicide even occurred, which may be difficult if it involves a more detailed exploration of a complex scenario involving things like pregnancy or life-support measures.

7.4.1 Causation

Causation is what led up to the crime itself. Because homicide requires the killing of one human being by another, it is vital to demonstrate that the killing of a human being was actually directly caused by another. This can get surprisingly tricky. There are two types of causations: factual and legal. Causation in fact means that one individual started a chain of events that led to the eventual death of another person. In more technical language, the Model Penal Code states, “Conduct is the cause of a result when…(a) it is an antecedent but for which the result in question would not have occurred” (Model Penal Code § 2.03(1)(a)). Basically, if the one person did not do what they did, the other person would still be alive.

Legal causation means that one individual did something they should have known would lead to the death of another person. Technically, the Model Penal Code states, the actual result cannot be “too remote or accidental in its occurrence to have a [just] bearing on the actor’s liability” (Model Penal Code § 2.03 (2) (b)). This means, it must be clear enough of a connection or outcome that a reasonable person could have foreseen or predicted that the end result would occur. This is called objective foreseeability.

There are additional legal rules and paths that make causation and assigning blame (criminal liability) far more complicated than can be summarized here. The extent of the criminal code is beyond the scope of this one book and this one class. For here and now, we are sticking to the basics to form a foundational understanding.

7.4.2 Non Criminal Homicide

It is important to note that homicide is not always criminal. For example, a lawful execution pursuant to the death penalty is not a criminal act. Also, a fully justified killing in self-defense is technically homicide, but it is not criminal homicide. Noncriminal homicides are considered either justifiable or excusable when one person admits to killing another, but meets the qualifications of either the appropriate actus reus or mens rea.

7.4.2.1 Justifiable Homicide

A justifiable homicide claim centers on the conduct of the person who committed the killing. In other words, it is all about the criminal action or actus reus. For example, in a case of legitimate self-defense, one person admits to killing another, but their criminal action was justified by the threat they believed to exist against themselves or someone else.

7.4.2.2 Excusable Homicide

An excusable homicide claim centers on the person’s mental state, or mens rea, when they committed the killing. For example, they admit to killing the victim, but can show their mental state was lacking due to some mental incapacity. You may have heard of this in cases where the defense claims the person’s act should be excused because of insanity.

As I am sure you can imagine, or have seen in movies and television shows, proving in court that a homicide was either justifiable or excusable is extremely difficult. Most homicides are considered criminal.