The American judicial system distinguishes between civil and criminal law. In a civil action the action is prosecuted by the injured party seeking redress for the wrong committed against him./her. The action is generally titled "John Smith vs. Betty Jones." In a criminal proceeding the action is prosecuted by the state by and agent of the government -specifically the district attorney. In a criminal proceeding the injured or aggrieved party  is only a witness. The injured  person is not a party to the legal  proceedings. In a criminal  proceeding the parties are the state and the person or persons charged with a criminal offense. The action is generally entitled "The People vs. John Smith"

Generally law schools make a distinction between criminal law and criminal procedure and they are often taught as two separate courses. Criminal Law deals with the "elements" of the offense, the conduct of the perpetrator, (acteus reus) "mens rea.",  the necessary mental state of mind  "mens rea.", and the defenses. Criminal Law for example deals whether the essential that are necessary to constitute the a particular crime. Criminal procedure on the other hand deals with the process by which the criminal action is prosecuted through court process for the purpose of establishing and proving the existence of the elements of the particular crime in question beginning with arrest, trial and the appellate process..

Common Law Defined:  When lawyers  and judges speak of "common law," they may mean either the law as it existed during the Common Law period in England or law that is derived from a process of judicial development.  The intended meaning frequently is evident from the context.  For example, the "common law process" typically refers to the process of judicial law-making, whether or not it occurs during the Common Law period.  "The Common Law rule" usually refers to the legal rule that existed in England during the Eighteenth Century.  On the other hand, a minority of states continue to rely upon judicially-modified variations of the original Common Law rule.  Such rules may be referred to as "common law" rules even if they are significantly different from the rule described by Blackstone. Paul H. Robinson, Fundamentals of Criminal Law, 2d ed., pg. 61,  Little Brown And Company (1995).

Current Role of Common Law:  While no state continues to permit judges to create crimes, the common law continues to be important for several reasons.  Some state criminal codes incorporate common law offenses by name, without defining them.  Under so-called "reception" statutes, judicial decisions must be relied upon to determine the requirements of a common law offense.  In addition, because some codes are simply codifications of the previously-existing common law doctrine, ambiguity in code language that calls for an examination of the drafters' intent may require review of the cases in which the doctrine was developed.  Similarly, the common law cases may be referred to because they tend to explain the rationale behind the original rule, where the codification of the rule frequently does not.  An attorney seeking to persuade a court of the wisdom, or folly, of the policy behind a particular interpretation of a statute may look to common law cases to establish and explain the policy.  An excellent discussion of  the rules and techniques of statutory interpretation can be found in  in Chapter 5, covering The Legality Principle, Fundamentals of Criminal Law. Paul H. Robinson, Fundamentals of Criminal Law, 2d ed., Little Brown And Company (1995).

A "crime" is any act or omission (of an act) in violation of a public law forbidding or commanding it. Crimes include both felonies (more serious offenses -- like murder or rape) and misdemeanors (like petty theft, or jaywalking). No act is a crime if it has not been previously established as such either by statute or common law.

Historically, most crimes have been established by state law, with laws varying significantly state to state. There is, however, a Model Penal Code (MPC) which serves as a good starting place to gain an understanding of the basic structure of criminal liability.

In recent years the list of Federal crimes has grown.

Federal Constitution and Statutes

• U.S. Constitution:
• Amendment IV - Search and Seizures
• Amendment VI - Criminal Prosecutions
• Amendment V - Due Process
• Amendment VIII - Excessive Bail and Cruel and Unusual Punishments 
• Amendment 14 - Equal Protection
• U.S. Code: 18 U.S.C., Part I - Crimes

Federal Agency Regulations

• Code of Federal Regulations: 28 C.F.R., Chapt. I - Dept. of Justice

Federal Judicial Decisions

• U.S. Supreme Court: Recent Criminal Law Decisions
• U.S. Circuit Courts of Appeals: Recent Criminal Law Decisions

State Statutes

• State Criminal Codes

• California Penal Code   

State Judicial Decisions

• N.Y. Court of Appeals:
• Criminal Law Decisions
• Sentencing Decisions
• Commentary from liibulletin-ny
• Appellate Decisions from Other States

Conventions and Treaties

• Dealing with Human Rights (Including in the Criminal Justice Context)

Key Internet Sources

• Federal Agencies:
• Federal Bureau of Investigation
• Drug Enforcement Administration
• Federal Bureau of Prisons
• Unites States Marshals Service
• Bureau of Alcohol, Tobacco, and Firearms
• U.S. Department of Justice
• House Committee on Government Reform, Subcommittee on Criminal Justice, Drug Policy and Human Resources
• House Judiciary Committee (includes information from Subcommittee on Crime)
• Buffalo Criminal Law Center
• Vera Institute Server
• United Nations Justice Network (UNCJIN)
• CopNet - Police Departments Around the Country and World
• Criminal Law Links (Emphasis on KY.)
• National Criminal Justice Reference Service
• Bureau of Justice Statistics
• Crime Statistics Links
• National Archive of Criminal Justice Data
• Nolo Legal Encyclopedia
• freeadvice.com
• ABA Criminal Justice Section
• National Criminal Justice Association
• Centre for Criminology Library, University of Toronto
• National Association of Criminal Defense Lawyers