Criminal Law and Procedure: Elements, Defenses, and the Fourth Amendment
Substantive criminal law
Every crime requires actus reus and mens rea, plus any attendant circumstances and a result. The mens rea levels to know are purpose, knowledge, recklessness, and negligence; questions often turn on which level attaches to which element. Transferred intent applies when the defendant intends harm to one person but harms another.
Inchoate offenses: attempt requires a substantial step plus specific intent; conspiracy requires an agreement plus an overt act in many jurisdictions, and the bilateral versus unilateral approach matters. Accomplice liability requires intent to aid and actual aid; mere presence is not enough.
Defenses
Self-defense requires reasonable belief in imminent unlawful force; imperfect self-defense mitigates rather than excuses. Insanity tests (M'Naghten, irresistible impulse, ALI) are frequently contrasted. Duress is generally not a defense to homicide.
Procedure and the Fourth Amendment
The exclusionary rule, the good faith exception, and standing are recurring traps. A search requires a warrant supported by probable cause unless an exception applies: search incident to arrest, automobile, plain view, consent, exigency, inventory, and stop-and-frisk (reasonable suspicion).
Miranda applies to custodial interrogation; the question is whether a reasonable person would feel free to leave. Confessions obtained in violation are excluded, but physical evidence derived from a voluntary statement may still be admissible.
Worked example
An officer stops a car for a broken taillight, smells marijuana, and searches the passenger compartment. That is a lawful automobile exception search if probable cause exists; a full search of the trunk requires probable cause to believe contraband is there.
Traps
- A Terry stop requires reasonable suspicion, not probable cause.
- Consent must be voluntary and may be limited in scope.
- The exclusionary rule does not apply to grand jury proceedings or civil proceedings.