All crimes have certain elements (“Criminal Law,” 2008, p.4). It is not material whether it is a crime against person, a crime against property or a crime against public order. These crimes in general have certain elements which must be proven in court before a conviction will follow.
The first element is the existence of a law which is based on the maxim that nullum crimen nulla poena sine lege. A person cannot be punished for his act or omission if there is no law which defines and punishes such act or omission.
Thus, there have been instances in the past where persons were not charged for a crime because there was no long punishing it. The requirement of a pre-existing law which defines and punishes an act or omission is also in accordance with Article 1 Section 9 of the US Constitution which provides that no bill of attainder or ex post facto law shall be passed. An Ex Post Facto Law is a law passed by the Legislature which makes criminal an act done before the passage of the law and which was innocent when done, and punishes such action.
The second element of a crime is that there must be criminal act or omission. Under existing laws, unless a person translates his thoughts into actions, his thoughts are beyond the reach of the criminal laws. The law requires that an act must be committed first and that the act must be one which the law considers as criminal. Moreover, the failure to do something may in certain instances be considered as a crime. There crimes are called illegal omissions which are simply “the failure to do what is required by law” (Patricia Smith, 2002, p.1). Thus, if under a law a person is required to wear clothing in public then failure to wear clothes in public is a crime. If under the law a person is required to protect or care for another person then failure to do so may subject him to criminal liability (“Criminal Law,” 2008, p.1).
The third element of a crime is intent. For a person to be held guilty of a crime it must be proved that he had the intent to act in a harmful way. Intent pertains to the state of mind or mental attitude of the person at the time of the criminal act. It is also called mens rea or guilty mind. Thus, it is common for crimes to be defined as intentionally, knowingly, maliciously, willfully, recklessly, or negligently bringing about a result or consequence of an act. Thus, when a person died by stepping on a wet cloth which caused him to slip and fall head first into the pavement, no crime is committed by the person leaving the wet cloth on the floor as it is not a criminal act. However, when a person drives recklessly into the highway and accidentally hits a pedestrian, a crime is committed regardless whether the driver had the criminal intent to kill the pedestrian as reckless driving is in itself a crime.
The fourth element of the crime is that the act and intent must occur at the same time. Thus, a wife who purchases a poison to kill her husband shall not be guilty of murder if she accidentally feeds him with spoiled food leading to his death. In this case, there was no intent to kill yet as feeding somebody with food is not in itself a crime.
All these elements must be established by the prosecution before an accused can be held guilty of a crime in a court of law and punished for the crime committed. If any of the elements of this crime is not proved then the accused is entitled to acquittal. Thus, the first defense available to the accused is to prove that any of the elements of the crime is lacking. If, on the other hand, the accused fails to establish the absence of any of these elements, there are other affirmative defenses that he can use.