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 condu