US Criminal Law

From Wikibooks, open books for an open world
Jump to: navigation, search

All crimes have the following four elements in common:

  1. a voluntary act known as actus reus.
  2. a culpable state of mind known as mens rea.
  3. “concurrence” between the mens rea and the actus reus.
  4. causation of harm (or risk).

Actus Reus[edit]


Actus Reus (Latin word for "guilty act") is the physical aspect of the crime. It can be an act or a failure to act where the person is required to act (e.g., a parent failing to protect their child). For example, the actus reus of battery is the physical contact between the assailant and victim. (except, please note that simple battery (without intent to do a further crime) is a tort, not a crime, so do not confuse these).

Another example would be theft. The crime of theft requires physically taking something away (the actus reus) along with the intent to deprive the owner of the property indefinitely (the mens rea).

1. Which of the following aspect of actus reus is not required?

(A) causation

(B) voluntariness

(C) intention

(D) physical capability

2. Which of the following could potentially constitute an actus reus?

(A) Uploading spyware in order to harm your friend's computer

(B) Hurting someone in the dream

(C) An assassin with a plan to kill someone but failed to act on the plan

Some special "act" such as possession can be actus reus.

For Example, possession of drug is a serious crime in many countries around the world. If possession is deemed a crime, the act of possession always is conscious possession- you need to be aware of the fact that there is cocaine in your bag. So here comes the "voluntary" aspect. An act cannot satisfy the actus reus requirement unless it is voluntary.

3. Does an act of reflex or convulsion give rise to criminal liability? No. (It is not voluntary.)

4. Does an act performed during a state of unconsciousness meet the actus reus requirement? No. (It is not voluntary.)

5. How about the acts performed under hypnosis? The court is split about this issue. The Model Penal Code considers conduct under hypnosis as involuntary.

Example: Mike Bookie, while taking the Criminal Law final exam, is stricken by epileptic convulsions and strikes John Wikie in the face. Since D did not hit John voluntarily, he does not have criminal liability. Some acts are not actus reus because they are not physical.

  1. Thoughts, words, possession and status

We cannot punish someone for mere thoughts of doing something harmful. For instance, I write here, "I intend to burn all the WikiBooks." This does not constitute arson nor any crime.


Two main types of causation exist, therefore two tests are applied:

  • 1. Was the criminal act foreseeable?
  • 2. But for the act of someone else, the criminal act would not have occurred.

Mens Rea[edit]

Mens Rea ("guilty mind") is the mental aspect of a crime that describes the criminal defendant's state of mind. The Model Penal Code gives four mens rea categories: purposely, knowingly, recklessly, negligently. While not used everywhere, those categories are typical. Some crimes (e.g., statutory rape) do not have a mens rea element because they are strict liability crimes.

Mens Rea (evil intent) is the mental aspect of a crime that describes the criminal defendant's necessary state of mind to constitute a conviction. There are Specific Intent (to commit the crime)(eg. assault with intent to commit murder), General Intent (most crimes - to do an act that constitutes a crime, a negligent act which leads to the commission of a crime - like speeding which leads to an accident which then results in death or injury to another), and violation per se/no intent (such as driving (not recklessly or negligently) above a posted speed limit).

Coincidence of Mens Rea & Actus Reus[edit]

Transferred Malice[edit]

In both criminal and tort (civil wrong) law, when an intent to cause harm to one person results in harm to another person instead of the intended target, the law transfers the intent to the actual harm. So, if Joe meant to kill James, but James ducked and Joe's bullet hits Sue, Joe can be charged with and found guilty beyond a reasonable doubt of the murder of Sue, though he intended to kill James.


Liability of Omissions[edit]

In Criminal law, people may be guilty of a crime based on their failure to act. For example, for failing to stop or report sexual abuse; also, one's failure to report a felony may be a criminal act. A person may also be charged with conspiracy unless he completely and voluntarily renounces participation in that conspiracy. This is a slightly different operation of criminal guilt by omission because the actor is engaged in a conspiracy until he completely and voluntarily renounces his participation. In some jurisdictions, the person may avoid criminal liability by stopping the conspiracy from achieving its aims.


Recklessness is one of the three mental states that constitute mens rea. Recklessness shows less w:culpability than intention and knowledge, but more culpability than criminal negligence. The test of any mens rea element is always based on an assessment of whether the accused had foresight of the prohibited consequences and desired to cause those consequences to occur. The three types of test are:

  1. subjective where the court attempts to establish what the accused was actually thinking at the time the actus reus was caused;
  2. objective where the court imputes mens rea elements on the basis that a reasonable person with the same general knowledge and abilities as the accused would have had those elements; or
  3. hybrid, i.e. the test is both subjective and objective.

The most culpable mens rea elements will have both foresight and desire on a subjective basis.

Recklessness usually arises when a person is aware of the potentially adverse consequences to the planned actions, but chooses to proceed anyway, exposing others to the risk of suffering the foreseen harm but not actually desiring that the victim be hurt.

Strict Liability[edit]

In general, Strict Liability is rarely imposed in criminal law. There has been some debate regarding strict liability for criminal offenses, as it removes the mental state (mens rea) as an element of the offense. Several strict liability criminal offenses, however, have been widely approved, such as driving while intoxicated and speeding. The basic point (and underlying societal judgment) is that proof of the act itself beyond a reasonable doubt is sufficient to show criminality.

Similarly, in civil law, strict liability will be imposed when an act is itself so hazardous to the community that intent is not a factor in determining if the perpetrator is to be held to account. If one engages in blasting and damages another's property it does not matter that there was no intention to do damage, nor that great care was exercised in planning and executing the blasting, the person doing the blasting is liable.


In Criminal law those who can be held accountable are those who perpetrate the unlawful act (the perpetrator), and those who somehow aid, promote or encourage the unlawful act (an accessory or aider and abetter). To be guilty as an "aider and abetter" one must somehow, with knowledge of the unlawful purpose of the perpetrator, aid promote or encourage the act. Both then are principals in the act and can each be held accountable for the acts of the other. A common example is the robbery and get away driver. Both are principals. If the inside man shot someone in the course and scope of the robbery, the get away driver is also responsible for the shooting, even though he never anticipated the shooting. Principals of Conspiracy permeate this concept.

Preliminary Offenses[edit]

Conspiracy & Incitement[edit]

A conspiracy involves an agreement to commit an unlawful act, and an act in furtherance of that unlawful act. A person found guilty of conspiracy to engage in a crime is generally less-harshly punished than one found guilty of that crime in itself. For example, robbery may be a second-degree felony where conspiracy to commit robbery would be a third-degree felony. In this way, conspiracies are like attempt crimes, which are also generally of a lesser degree. (Disagree with above). Conspiracy to commit a crime (an agreement + an act infurtherance of unlawful act) causes the conspirator to be culpable for the completed act unless there is a clear expression of a withdrawal from the conspiracy. Thus, in a conspiracy to commit murder where, for example, a car is provided to the co-conspirator, with the knowledge that the co-conspirator is going to commit the murder is sufficient for both to be sentenced for murder.

Due process[edit]

Due process is a legal concept that when followed helps protect the people's fundamental rights in their dealings with the legal system. Due process is guaranteed by the Fifth Amendment and Fourteenth Amendment. Both state "No person shall be deprived of life, liberty, or property, without due process of law."

"Due process" includes (1) the right to be notified of charges or proceedings (2) the right to be tried by an impartial judge, magistrate or jury (3) the right to defend oneself in a court of law (4) the right to a trial under the established procedures and (5) the right to be cleared of charges if not convicted. Additionally, due process requires that a person cannot be charged under a law that does not exist. The Bill of Rights defines the minimum standards of due process that is required of the government.

Due process ensures that a person receives a fair trial and helps protect the innocent from being wrongly convicted.

Search and Seizure[edit]

The Fourth Amendment to the United States Constitution states “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue; but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.” The courts in interpreting this have determined that searches conducted with a search warrant are assumed to be reasonable and searches without a search warrant are assumed to be unreasonable and therefore illegal. However the courts have also determined several exceptions to the requirement of a search warrant. For a warrant to issue, there must be these five requirements:

(1) Probable cause (2) Oath or affirmation of probable cause (3) Particularly describing places to be searched, and what is to be searched for and/or seized (4) Signed by the Judicial Branch (a judge, essentially) (5) Executed by the Executive Branch (the police, in general)


There are four main types of legal defenses. They are Alibi, Justifications, Excuses and Procedural Defenses.


When a defendant uses an argument based upon an alibi they are not only saying they are not guilty, but they are claiming to be innocent. The alibi is based upon the idea that they could not have committed that crime because they were elsewhere when the crime was committed. Typically in a criminal trial, the defense will attempt to assert proof of an alibi. Such proof can come from documentation of the defendant's whereabouts or testimony of someone who was with the defendant at the relevant time.

In law school, this is commonly called the "SODDI" defense..."Some Other Dude Did It". Lawyers call it "alibi."


Justification defense requires the defendant to admit they committed the crime, but they are not guilty because committing the crime was the lesser of two evils. Self defense is the best known of this type of defense.

Excuse defenses[edit]

The Excuse defenses are based on the idea that the person, while they did commit the crime and the action was not justified, did not have the control or state of mind at the time the crime was committed to be held legally responsible for the crime. Insanity is the best known of the excuse defenses. Also, mitigating circumstances can lead to an acquittal, or a more lenient sentence, if convicted.

Procedural defenses[edit]

The fourth and least common of the main types of defenses are procedural defenses. Procedural defenses include things such as entrapment, police fraud, prosecutorial misconduct and denial of a speedy trial. These types of defenses argue that the legal system has failed and the person should therefore be released.

Innovative defenses[edit]

Innovative defenses are somewhat special types of defenses. They are relatively new and untried, with little or no precedent bearing upon them. Previously tried innovative defenses include "Twinkie defense", "black rage", Asperger's Syndrome and urban survival syndrome. Generally, defendants use these defenses to introduce reasonable doubt into the proceedings. Because of this, precedent could be developed, but probably only when judges refuse to admit evidence of these defenses. At that point, the question becomes one of relevance, and a holding on appeal that such evidence is or is not relevant almost always depends on the facts of the cases. As such, it should not be surprising that the reported cases discuss little of these theories.


Wikibooks contains books on many legal topics; however, no warranty whatsoever is made that any of the books are accurate. There is absolutely no assurance that any statement contained in an book touching on legal matters is true, correct, or precise. Law varies from place to place and it evolves over time—sometimes quite quickly. Even if a statement made about the law is accurate, it may only be accurate in the jurisdiction of the person posting the information; as well, the law may have changed, been modified or overturned by subsequent development since the entry was made on Wikibooks.

The legal information provided on Wikibooks is, at best, of a general nature and cannot substitute for the advice of a licensed professional, i.e., by a competent authority with specialized knowledge who can apply it to the particular circumstances of your case. Please contact a local bar association, law society or similar association of jurists in your legal jurisdiction to obtain a referral to a competent legal professional if you do not have other means of contacting an attorney-at-law, lawyer, civil law notary, barrister or solicitor.

Neither the individual contributors, system operators, developers, nor sponsors of Wikibooks nor anyone else connected to Wikibooks can take any responsibility for the results or consequences of any attempt to use or adopt any of the information or disinformation presented on this web site.

Nothing on or of any project of Wikimedia Foundation Inc., should be construed as an attempt to offer or render a legal opinion or otherwise engage in the practice of law.