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Criminal Law: Home

A guide designed for first year law students on the MU Law Library's resources regarding Criminal Law

Subject Explanation


criminal law: an overview

Criminal law involves prosecution by the government of a person for an act that has been classified as a crime. Civil cases, on the other hand, involve individuals and organizations seeking to resolve legal disputes. In a criminal case, the state, through a prosecutor, initiates the suit, while in a civil case the victim brings the suit. Persons convicted of a crime may be incarcerated, fined, or both. However, persons found liable in a civil case may only have to give up property or pay money, but are not incarcerated.

A "crime" is any act or omission (of an act) in violation of a public law forbidding or commanding it. Though there are some common law crimes, most crimes in the United States are established by local, state, and federal governments. Criminal laws vary significantly from state to state. 

Crimes include both felonies (more serious offenses -- like murder or rape) and misdemeanors (less serious offenses -- like petty theft or jaywalking). Felonies are usually crimes punishable by imprisonment of a year or more, while misdemeanors are crimes punishable by less than a year. However, no act is a crime if it has not been previously established as such either by statute or common law. Recently, the list of Federal crimes dealing with activities extending beyond state boundaries or having special impact on federal operations, has grown. See Title 18.

All statutes describing criminal behavior can be broken down into their various elements. Most crimes (with the exception of strict-liability crimes) consist of two elements: an act, or "actus reus," and a mental state, or "mens rea". Prosecutors have to prove each and every element of the crime to yield a conviction. Furthermore, the prosecutor must persuade the jury or judge "beyond a reasonable doubt" of every fact necessary to constitute the crime charged. In civil cases, the plaintiff needs to show a defendant is liable only by a "preponderance of the evidence," or more than 50%.

Text and links copied from LII's (Cornell University Law School) Criminal Law page.  Links will take you to definitions and/or further explanations of the terms highlighted by Cornell Law





Databases and Electronic Resources

There is good information to be had online through WestlawNext and Lexis Advance, as well as other providers.  Though this list should in no way be considered comprehensive, a few of the best are listed below:


Wharton's Criminal Law

Missouri Practice Series, Criminal Law



Missouri Bar CLE on Criminal Practice



Study Aids


CALI (Computer Assisted Legal Instruction) has several good interactive lessons pertaining to Criminal Law available here.

You will need your student password, which can be obtained at the reference desk or computer lab or IT help desks. 

Below is a list of subjects which may help you in your classwork, along with their links.  Many more subjects are available at the CALI link above.

Lessons: Criminal Law

Actus Reus
40 minutes

35 minutes

Constitutional Limitations: 8th Amendment
35 minutes
Defense of Others
25 minutes

Duty to Retreat

25 minutes
Excuses II: Insanity and Infancy
30 minutes

Homicide (Causation)
Homicide (Causation - Part II)
45 minutes (25 minutes without the essay)
Homicide (Felony Murder)
45 minutes (25 minutes without the essay)
Homicide (Involuntary Manslaughter)
45 minutes (25 minutes without the essay)
Homicide (Murder by Degrees)
45 minutes (25 minutes without the essay)
Homicide (Murder)
35 minutes (20 minutes without the essay)
Homicide (Unlawful Act Manslaughter)
40 minutes (25 minutes without the essay)
Introduction to Homicide
25 minutes
Justification Defenses: Excuse Defenses Distinguished
30 minutes
Mistake as to the Law Defining the Offense
25 minutes
Punishment: Theories
30 minutes
25 minutes
Sources of Criminal Law
10 minutes
The Mens Rea of Attempts
20 minutes
The Mens Rea of Knowledge
20 minutes
The Mens Rea of Negligence
20 minutes
Lesson Completion Time: 20 minutes