This episode offers a comprehensive overview of criminal law in the United States, distinguishing it from civil law and outlining its foundational principles. They clarify key components necessary for proving criminal liability, such as actus reus (the guilty act) and mens rea (the guilty mind), explaining that a voluntary act and a culpable mental state are generally required for conviction. The texts also detail various categories of substantive crimes, including different degrees of homicide, property crimes like robbery and burglary, and crimes against persons such as assault and rape, often contrasting common law definitions with modern statutory interpretations. Furthermore, the sources cover essential criminal defenses like self-defense, duress, mistake of fact or law, and insanity, discussing the legal standards and burdens of proof associated with each. Finally, the materials touch upon the purposes of punishment within the justice system and explore the complexities of conspiracy laws and corporate criminal liability.

Criminal law addresses crimes and their consequences, where society as a whole is theoretically damaged and responsible for prosecution. Civil law, in contrast, handles non-criminal disputes between private parties. An overarching purpose of criminal law is to prevent conduct that causes or may cause harm to people or society.

The "voluntary act" requirement (actus reus) ensures that a conviction is based on an action willingly taken and attributable to the defendant's voluntary efforts. A "status," such as being addicted to illegal drugs, cannot be criminalized; rather, it is the voluntary use of drugs that is punishable.

Mens rea, or "guilty mind," describes the expected mental state of an accused at the time of the criminal act. Acting "purposely" means the defendant's conscious objective was to cause the criminal conduct or result, while acting "knowingly" means the defendant was aware that their conduct was practically certain to cause the result.

Concurrence occurs when the actus reus (the criminal act) and mens rea (the criminal intent) are present and linked. This means the defendant's physical action must reflect their criminal mental state for a crime to be established.

An accomplice is a "principal in the second degree" who aids, counsels, assists, or encourages the person who commits the crime. For a party to be considered an accomplice, presence (which can be constructive) and an affirmative action taken with the requisite criminal intent are typically required.

Inchoate crimes are offenses that are preparatory or incomplete, meaning the criminal act has not yet been fully carried out. Two examples are "attempt" and "solicitation."

Robbery is classified as a crime against persons, unlike other theft crimes which are typically against property. This distinction arises because robbery involves the use or threat of force against a person, making the victim's safety and well-being central to the offense.

The M'Naghten test for insanity focuses on whether, at the time of the criminal act, the defendant suffered from a "disease of the mind" that prevented them from either knowing the nature and quality of their act or knowing that the act was wrong. It is primarily a cognitive test.

Intoxication can serve as a defense if it is involuntary and causes a complete lack of capacity, similar to insanity. Voluntary intoxication, however, typically only negates specific intent crimes but not general intent crimes.

A "mistake of fact" occurs when a defendant misunderstands a fact that negates an element of the crime, and this mistake must be honest and reasonable. A "mistake of law" involves misunderstanding the legal status of one's actions, and is generally not a defense unless based on an official statement of the law. Mistake of fact is generally more successful as a defense.