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Overview of Criminal Law - Module 1 of 5

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Module 1: Overview of Criminal Law


Reasons for Punishing Crime

            When we think about crime, we instinctively understand the need for punishment and accountability. After all, without recognized rules of behavior and systems for dealing with rule-breakers, societies could not maintain order. Still, reasons for criminal laws and criminal punishments can be broken down into five categories: 


2.    Deterrence

3.    Incapacitation

4.    Rehabilitation

5.    Restitution


            When someone is victimized by crime, a feeling or need to exact revenge is often invoked.  This need for revenge is often felt by the victim, the victim’s friends and family and even by members of society at large, especially when they learn the details of a particularly infamous or cruel crime. When a government adequately punishes criminals, victims feel satisfied and society gains trust in the criminal justice system to do its job. Many of the justifications for the death penalty boil down, in one form or another, to retribution.


            Deterrence is the idea that crime can be prevented if people are afraid of the consequences. It can apply to a single defendant who may be deterred from committing a particular crime for a second time if he is adequately punished the first time, a phenomenon known as “special” or “specific” deterrence. It can also apply to society as a whole by making an example out of one defendant to deter others from committing similar acts. This is known as “general deterrence.”


            Incapacitation removes criminals from society altogether and makes it impossible or more difficult for a criminal to commit future crimes for a period of time. For example, while a bank robber is incarcerated, he is unable to commit more bank robberies. Execution, of course, results in permanent incapacitation, though punishments short of death (such as life imprisonment) can typically also incapacitate. As such, incapacitation is not generally thought of as justification for the death penalty.


            Often, criminals are able to change their behavior to conform to the rules of society. Counseling, drug and alcohol treatment and vocational training may be offered to criminals or may be ordered as alternatives to incarceration if a court believes a defendant can be reformed. The goals of these programs are to prepare and equip defendants to lead crime-free lives.


            Restitution is a payment the court orders a defendant to pay to a victim. These payments are designed to compensate a victim for physical injury, monetary loss, property loss or other distress. Fines may also be imposed to recoup court costs and other expenses. The simplest example of restitution, which is universally ordered as part of sentences, would be the order for a convicted thief to repay the money she stole.

Components of Crimes

Criminal acts can be broken down into two major components: actus reus and mens rea.  Actus reus is a Latin term meaning “guilty act” and mens rea is a Latin term meaning “guilty mind.”

            In order to punish, our criminal justice system typically requires proof of both components. A defendant must commit the criminal act and do so with a culpable mental state. The only exception is for strict liability crimes (such as traffic infractions and other typically minor crimes), which do not require proof of a specific mental state. 

Actus Reus

A criminal act must be voluntary[1]. If a defendant’s conduct is the result of a spasm, reflex, or other unconscious movement, it is not an actus reus.[2] However, a failure to act, in some cases, can form the basis of actus reus if the law imposes a legal duty to act or if the omission is included in the definition of the offense[3].

For example, if a person suffers a seizure and involuntarily hits another person next to him on the street, he has not committed assault. Even aside from his innocent mental state, he has not voluntarily committed any act at all. He therefore cannot be found guilty of a crime. However, if he had a history of seizures and was instructed never to operate a car, but he did drive, suffered a seizure and injured someone, he could be found guilty of a crime. The actus reus would be driving the car in the first place, not necessarily the involuntary motions undertaken while stricken with the seizure.  

Let’s look at another example. Assume an expert swimmer is at a public swimming pool and no lifeguard is on duty. The swimmer sees a child flailing around in the deep end of the pool and does nothing to help, allowing the child to drown. In nearly every jurisdiction, failure to rescue is not a crime. Thus, she would not be guilty of a crime. However, the law or an agreement does sometimes impose a duty of care, as in the case of a parent-child or babysitter-charge. If the expert swimmer was the child’s mother or babysitter, for example, failing to rescue the child may be considered manslaughter.

A small number of states have “duty to assist” laws that require a bystander to assist someone in need of rescue. In those jurisdictions, the failure to act could serve as the basis for an actus reus.[4]

Mens Rea

            Mens rea refers to criminal intent in committing an act. Precise definitions may vary from state to state, but the following levels and definitions of mens rea are generally accepted[5]:

Negligence – A person knew, or should have known, of a substantial risk that the illegal or dangerous conduct would occur and acted in the risky manner nonetheless

Recklessness – A person consciously disregarded a substantial risk

Knowledge – A person is aware that conduct will cause an illegal or dangerous result

Purpose – A person acts with intent that his action causes a particular result.

Consider the following scenarios:

1.    Joe is angry with Mike and decides to kill him.  Joe deliberately purchases a gun, lies in wait and shoots Mike in the head, intending to kill him. Joe has acted purposefully.

2.   Joe is angry with Mike and decides to kill him. Joe obtains a car bomb to plant on Joe’s car, intending to kill him. Joe knows that Mike’s son, Timmy, will also be in the car, but plants the car bomb anyway. Joe has acted purposefully to kill Mike, but not purposefully to kill Timmy. Mike’s intent was not to kill Timmy, but he was aware that his conduct would kill Timmy. Thus, his action towards Timmy is considered “knowingly.”

3.   Joe and Mike are neighbors. Joe knows that Mike often jogs through the neighborhood. Joe decides to drag race in the street against his friend, Jane. While racing, Joe hits and kills Mike. Joe has acted recklessly because he disregarded a substantial risk when he chose to drag race on a populated street.

4.    Joe drives 20 miles per hour over the speed limit down his street. He loses control of his car and accidentally hits and kills Mike. Joe has acted negligently because he should have been aware of a substantial risk of speeding in a populated neighborhood.

Many criminal statutes specify the required level of mens rea for the statute to apply. For example, an involuntary manslaughter statute might specify that the defendant must behave recklessly or with criminal negligence. In Arizona, for example, murder in the first degree must be intentional or knowing.[6] Thus, a negligent or reckless mental state will not support a conviction for first degree murder. Manslaughter, however, is defined as “recklessly causing the death of another person.”[7] Thus, a reckless mental state will support a conviction for manslaughter, but negligence will not.

If the statute does not specify, the requisite mental state must be established by case law, where courts will infer the requisite level of mens rea from ascertainable legislative intent, the common law definitions of the relevant crimes and general principles of criminal law.


            There must be concurrence between the actus reus and mens rea, which means that the two components must occur simultaneously. Consider the following example: Joe accidentally (without negligence or recklessness) struck and injured a jogger- Mike- with his vehicle. Once Joe realized he had injured Mike, he expressed glee because Mike was his sworn enemy, and expressed happiness that Mike is hurt and the wish that Mike die from his injuries. No crime occurred because there was no concurrence between the actus reus and the mens rea.


            Causation is another necessary element to convict a defendant of a crime. Causation consists of the elements of actual cause and proximate cause. Actual cause is sometimes referred to as “cause-in-fact” or “but-for” cause. A defendant is the actual cause if “but for” his conduct, the result would not have occurred. Proximate cause is sometimes known as “legal cause” and requires that a result be a foreseeable consequence of the defendant’s conduct.  Consider the following example: Joe intentionally struck Mike with a bat and injured him. While Mike was in the hospital, Nurse Nancy entered Mike’s room and injected Mike with the wrong amount of pain medication and Mike died of an overdose.  Joe’s act was the but-for cause, but not the proximate cause of Mike’s death, as gross medical malpractice is not generally foreseeable.


Constitutional Limitations

Principle of Legality and Fair Notice

            That an act may be immoral or unethical is not enough for it to be considered criminal. Conduct must be defined as a crime at the time it is performed to be punishable. The statute defining the crime must be clear so that a person of ordinary intelligence could understand its meaning and what conduct it prohibits. If a statute is too vague or overbroad, it may be struck down as unconstitutional. Further, the wording must not make it vulnerable to discriminatory enforcement.[8]

Ex Post Facto Laws

            Legislatures are not allowed to enact laws that punish conduct retroactively. For example, if a law is passed today that forbids dumping hazardous waste into a local river, a person cannot be prosecuted for dumping hazardous waste the day before the statute was signed into law, even if the same reasons that the action was wrong existed the day before the law was signed as the day after, and the rule applies even if it was apparent that the law would be signed at the time of the action. Similarly, legislatures are not allowed to increase the punishment for offenses retroactively. The statutory maximum sentence as of the date of the offense is the maximum punishment that can be meted out.

Punishing a Status

            A person may not be punished for a status. For example, it is unconstitutional to criminalize drug addiction or alcoholism. It is constitutional to punish certain behaviors, however, such as public intoxication, drunk driving or possession of illegal drugs, even if those actions arose from or were caused by status, addiction or dependence.

Cruel and Unusual Punishment

            The Eight Amendment to the Constitution prohibits cruel and unusual punishment. In the landmark case of Furman v. Georgia[9], the United States Supreme Court provided the following four ways in which punishment can be considered cruel and unusual:

  • The "essential predicate" is "that a punishment must not by its severity be degrading to human dignity," especially torture.
  • A punishment is cruel and unusual if it is “obviously inflicted in wholly arbitrary fashion."
  • A punishment is cruel and unusual if it "is clearly and totally rejected throughout society." and
  • A punishment is cruel and unusual if it "is patently unnecessary."

Sources of Criminal Law

Constitutional Law

            The highest source of law is the United States Constitution. It protects private individuals from governmental action and the Bill of Rights, its first 10 amendments, is the source of protection of many of our most basic individual rights. In addition to the U.S. Constitution, each state has a constitution. Most state constitutions are similar to the U.S. Constitution, but sometimes they provide additional protections for individuals. For example, the Vermont Constitution abolished slavery in 1777[10] and the U.S. Constitution did not do so until 1865.[11]

            Constitutions rarely establish crimes, but they are the primary sources of limitations on what governments can punish. The Bill of Rights contains a litany of criminal procedure rights, including the right to counsel, the right to trial by jury and protection from unreasonable searches and seizures.  

Statutory Law

            A statute is a written law passed by the legislature. On the federal level, that’s Congress, while state legislatures are their counterparts. Federal prosecutors – the Department of Justice, as represented by United States Attorneys in almost 100 federal districts around the country - prosecute defendants who commit federal crimes, while state governments – typically district attorneys - prosecute defendants for committing state crimes. While statutory law is an important component of almost all areas of law, it’s especially important in the context of criminal law. That is because, without exception, all criminal prosecutions must allege a violation of a specific piece of criminal law legislation. By contrast, in areas such as contracts or torts, applied law may be based on case or common law, without corresponding statutes.

Case Law

            Case law means law that is derived from judicial opinions. As the rulings become law, they set precedents for how similar cases will be decided in the future. This policy is called stare decisis. While courts are only bound by decisions of courts that are directly above them (for example, a Florida district court is bound by the decisions of the Florida Supreme Court, but not the decisions of the Georgia Supreme Court or even federal appellate courts in Florida), decisions from other cases may be accepted as persuasive authority.

Model Penal Code

            Criminal laws can vary widely among the states. As a result, a group of scholars got together in the 1960s to draft the Model Penal Code. The purpose was to provide a set of criminal statutes that states could adopt in order to provide more consistency in the criminal codes. While no state has adopted the Model Penal Code as its entire body of criminal law, many states have adopted at least parts of it and it has influenced other state laws and judicial interpretations.


            After a defendant pleads guilty or is found guilty by a jury, a judge must determine an appropriate sentence. Criminal laws provide ranges of possible sentences and the judge must determine where in the range the appropriate sentence lies. Judges are generally afforded great discretion in these determinations, though sentences, like criminal convictions, can be appealed.

            Note that, in death penalty cases, a jury must vote for the death sentence before a judge can impose it.[12]

            Sentences can range in severity from fines and probation to prison time and the death penalty. Sentencing laws and procedures vary depending on the jurisdiction. The federal government and some states have adopted sentencing guidelines[13] that assist the judge in determining the appropriate sentence, but because each state is independent, the content of these guidelines varies widely.

            The United States Sentencing Commission established the Federal Sentencing Guidelines for the purpose of reducing sentencing disparities among federal defendants. However, these guidelines are advisory only and federal judges are not required to follow them. In addition to the underlying criminal acts, the Guidelines call for the judge to consider factors such as the amount stolen in theft cases, the vulnerability of the victims, the level of planning and number of conspirators involved and the defendant’s criminal history.  They also provide for reduced sentences if a defendant accepts responsibility and cooperates with law enforcement.

            In our next module, we’ll focus on inchoate crimes, which are crimes that do not require completion of an act or result. This primarily includes attempt, conspiracy, criminal solicitation and liability as an accessory.

[8] See United States v. Nelson, 712 F.3d 498, 504 (11th Cir. 2013).

[9] Furman v. Georgia, 408 U.S. 238, 281 (1972).

[12] Ringv. Arizona, 536 U.S. 584, 609 (2002).

[13] 2018 Guidelines Manual, U.S. Sentencing Comm, https://www.ussc.gov/guidelines (Nov. 1, 2018).