30 Section 3.3: Elements of Crimes

The legal definitions of all crimes contain certain elements. If the government cannot prove the existence of these elements, it cannot obtain a conviction in a court of law. Other elements are not part of all crimes, but are only found in crimes that prohibit a particular harm. Often, a difference in one particular element of a crime can distinguish it from another related offense, or a particular degree of the same offense. At common law, for example, manslaughter was distinguished from murder by the mental element of malice aforethought.

  The Criminal Act

Nobody can read minds, and the First Amendment means that people can say pretty much whatever they want. What you think and say (within limits) is protected. It is what you do-your behaviors-that the criminal law seeks to regulate. Lawyers use the legal Latin phraseactus reus to describe this element of a crime. It is commonly translated into English as the guilty act. The term act can be a bit confusing. Most people tend to think of the term act as an action verb-it is something that people do. The criminal law often seeks to punish people for things that they did not do. When the law commands people to take a particular action and they do not take the commanded action, it is known as an omission. The law commands that people feed and shelter their children. Those who do not are guilty of an offense based on the omission. The law commands that people pay their income taxes; if they do not pay their taxes, the omission can be criminal. Threatening to act or attempting an act can also be the actus reus element of an offense.

In addition to acts and omissions, possession of something can be a criminal offense. The possession of certain weapons, illicit drugs, burglary tools, and so forth are all guilty acts as far as the criminal law is concerned. Actual possession is the legal idea that most closely coincides with the everyday use of the term. Actual possession refers to a person having physical control or custody of an object. In addition to actual possession, there is the idea of constructive possession. Constructive possession is the legal idea that the person had knowledge of the object, as well as the ability to exercise control over it.

  Criminal Intent

A fundamental principle of law is that to be convicted of a crime, there must be a guilty act (the actus reus) and a culpable mental state. Recall that culpability means blameworthiness. In other words, there are literally hundreds of legal terms that describe mental states that are worthy of blame. The most common is intent. The Model Penal Code boils all of these different terms into four basic culpable mental states: purposely, knowingly, recklessly, and negligently.

Purposely . According to the Model Penal Code, a person acts purposely when “it is his conscious object to engage in conduct of that nature….”

Knowingly . A person acts knowingly if “he is aware that it is practically certain that his conduct will cause such a result.” In other words, the prohibited result was not the actor’s purpose, but he knew it would happen.

Recklessly . A person acts recklessly if “he consciously disregards a substantial and unjustifiable risk.” Further, “The risk must be of such a nature and degree that, considering the nature and purpose of the actor’s conduct and the circumstances known to him, its disregard involves a gross deviation from the standard of conduct that a law-abiding person would observe in the actor’s situation.”

Negligently . A person acts negligently when “he should be aware of a substantial and unjustifiable risk that the material element exists or will result from his conduct.” The idea is that a reasonably carefully person would have seen the danger, but the actor did not.

At times, the legislature will purposely exclude the mens rea element from a criminal offense. This leaves only the guilty act to define the crime. Crimes with no culpable mental state are known as strict liability offenses. Most of the time, such crimes are mere violations such as speeding. An officer does not have to give evidence that you were speeding purposely, just that you were speeding. If violations such as this had a mental element, it would put an undue burden on law enforcement and the lower courts. There are a few instances where serious felony crimes are strict liability, such as the statutory rape laws of many states.


For an act to be a crime, the act must be brought on by the criminal intent. In most cases, concurrence is obvious and does not enter into the legal arguments. A classic example is an individual who breaks into a cabin in the woods to escape the deadly cold outside. After entering, the person decides to steal the owner’s property. This would not be a burglary (at common law) since burglary requires a breaking and entering with the intent to commit a felony therein. Upon entry, the intent was to escape the cold, not to steal. Thus, there was no concurrence between the guilty mind and the guilty act.

  Criminal Harm and Causation

In criminal law, causation refers to the relationship between a person’s behavior and a negative outcome. Some crimes, such as murder, require a prohibited outcome. There is no murder if no one has died (although there may be an attempt). In crimes that require such a prohibited harm, the actus reus must have caused that harm.

Key Terms

Actual Possession, Actus Reus, Causation, Concurrence, Constructive Possession, Elements (of crimes), Harm, Knowingly, Malice Aforethought, Model Penal Code, Negligently, Omission, Possession, Purposely, Recklessly


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