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1.1 Introduction

Learning Objective

  1. Define a crime.

This textbook introduces you to our legal system in the United States, the basic elements of a crime, the specific elements of commonly encountered crimes, and most criminal defenses. Criminal law always involves the government and government action, so you will also review the pertinent sections of the United States Constitution and its principles as they apply to criminal law. By the end of the book, you will be comfortable with the legal framework that governs the careers of criminal justice professionals.

Definition of a Crime

Let’s begin at the beginning by defining a crimeAn act committed in violation of a law prohibiting it or omitted in violation of a law ordering it.. The most basic definition of a crime is “an act committed in violation of a law prohibiting it, or omitted in violation of a law ordering it.”, “Definition of Crime,” accessed August 15, 2010, You learn about criminal act and omission to act in Chapter 4 "The Elements of a Crime". For now, it is important to understand that criminal act, omission to act, and criminal intent are elements or parts of every crime. Illegality is also an element of every crime. Generally, the government must enact a criminal law specifying a crime and its elements before it can punish an individual for criminal behavior. Criminal laws are the primary focus of this book. As you slowly start to build your knowledge and understanding of criminal law, you will notice some unique characteristics of the United States’ legal system.

Laws differ significantly from state to state. Throughout the United States, each state and the federal government criminalize different behaviors. Although this plethora of laws makes American legal studies more complicated for teachers and students, the size, cultural makeup, and geographic variety of our country demand this type of legal system.

Laws in a democratic society, unlike laws of nature, are created by people and are founded in religious, cultural, and historical value systems. People from varying backgrounds live in different regions of this country. Thus you will see that different people enact distinct laws that best suit their needs. This book is intended for use in all states. However, the bulk of any criminal law overview is an examination of different crimes and their elements. To be accurate and representative, this book focuses on general principles that many states follow and provides frequent references to specific state laws for illustrative purposes. Always check the most current version of your state’s law because it may vary from the law presented in this book.

Laws are not static. As society changes, so do the laws that govern behavior. Evolving value systems naturally lead to new laws and regulations supporting modern beliefs. Although a certain stability is essential to the enforcement of rules, occasionally the rules must change.

Try to maintain an open mind when reviewing the different and often contradictory laws set forth in this book. Law is not exact, like science or math. Also try to become comfortable with the gray area, rather than viewing situations as black or white.

Key Takeaway

  • A crime is an act committed in violation of a law prohibiting it or omitted in violation of a law ordering it. In general, the criminal law must be enacted before the crime is committed.


Answer the following question. Check your answer using the answer key at the end of the chapter.

  1. Read Gonzales v. Oregon, 546 U.S. 243 (2006). Did the US Supreme Court preserve Oregon’s right to legalize physician-assisted suicide? The case is available at this link: