CJ 100 Lecture Notes - Lecture 17: Mens Rea, Comprehensive Crime Control Act Of 1984
Legal Elements of a Crime
All crimes feature certain elements. Unless the government is able to prove the existence of these
elements, it can't obtain a conviction in a court of law.
No crime without law
There can be no crime without law. If an act is to be prohibited, a legally authoritative
body (such as Congress or a state legislature) must spell out in advance what behavior
is banned. The U.S. Constitution forbids ex post facto laws, which declare certain acts
to be illegal after the behavior occurs. The Constitution also requires that criminal laws
be written in precise terms so that a citizen can determine what conduct is illegal.
No crime without a criminal act
In American criminal justice, the government punishes people for what they do rather
than for what they think or say. The First Amendment protects an individual's freedom of
thought and speech. The failure to act, however, can be a crime in situations in which
an individual has a legal responsibility to do something. Tax laws and child neglect laws‐
are two examples. Threatening to act and attempting a criminal act can both be criminal
offenses. Similarly, conspiring to commit a crime is illegal. Conspiracy statutes
criminalize taking steps to carry out a plan to commit a crime.
No crime without intent
Intent pertains to the state of mind or mental attitude with which a person does an act. A
synonym for intent, mens rea, literally means “guilty mind”. The mental design or
purpose to commit a crime is the essence of intent.
No crime without concurrence
For an act to be a crime, both the act and the intent must occur at the same time.
Legal Defenses, Justifications for Crimes
For an act to be a crime, it must be not only intentional and in violation of a criminal law, but
also without defense or justification. Defense refers to situations that can mitigate guilt in a
criminal case. Two common defenses are insanity and entrapment. Justification is any just
cause for committing an act that otherwise would be a crime. Self‐defense is a prime example.
Insanity
Insanity is a legal term, not a medical term. It refers to any unsoundness of mind,
mental defect, or lack of reason that prevents people from distinguishing right from
wrong and from understanding the consequences of their actions. Guilty defendants can
be found “not guilty by reason of insanity” because of the belief that people should be
punished for their crimes only if they could control their behavior and knew what they
were doing was wrong. Otherwise, it is improper to hold people morally accountable for
criminal behavior.
Courts use several tests of insanity. Under the M'Naghten rule (1843), defendants are
considered not guilty by reason of insanity if at the time of the crime they were unable to
distinguish right from wrong. All federal courts and about half of the state courts have
the Model Penal Code's substantial capacity test. A person is not responsible for
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Document Summary
Unless the government is able to prove the existence of these elements, it can"t obtain a conviction in a court of law. If an act is to be prohibited, a legally authoritative body (such as congress or a state legislature) must spell out in advance what behavior is banned. The u. s. constitution forbids ex post facto laws, which declare certain acts to be illegal after the behavior occurs. The constitution also requires that criminal laws be written in precise terms so that a citizen can determine what conduct is illegal. In american criminal justice, the government punishes people for what they do rather than for what they think or say. The first amendment protects an individual"s freedom of thought and speech. The failure to act, however, can be a crime in situations in which an individual has a legal responsibility to do something. Tax laws and child neglect laws are two examples.
