Memory tricks for mens rea, actus reus, crimes & defenses
Criminal law is the state versus the individual — and every crime has elements the prosecution must prove beyond a reasonable doubt. From mens rea and actus reus to homicide degrees to defenses like insanity and self-defense, these memory tricks lock in the criminal law framework fast.
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Elements of Crime
MA + AC
Mens Rea · Actus Reus + Attendant Circumstances · Causation
The Building Blocks of Every Crime
Every crime requires a guilty mind (mens rea) plus a guilty act (actus reus). MA + AC: Mens Rea (criminal intent) · Actus Reus (voluntary act or omission) · Attendant Circumstances (required facts) · Causation (for result crimes). The prosecution must prove every element beyond a reasonable doubt.
Mens rea
Guilty mind — the mental state required. MPC levels: purposely, knowingly, recklessly, negligently. Common law: specific vs. general intent.
Actus reus
Voluntary act or culpable omission. Reflex actions, sleepwalking, and acts under duress are NOT voluntary — no actus reus.
Attendant circumstances
Required facts that must exist — e.g., for statutory rape, the victim must be under the age of consent.
Omission liability
Failure to act is criminal only with a legal duty: statute, contract, relationship (parent/child), voluntary assumption, or creation of peril.
Mens Rea Levels
PKRN
Purposely · Knowingly · Recklessly · Negligently
MPC's 4 Levels of Criminal Intent
The Model Penal Code ranks criminal intent from most to least culpable. PKRN — think of it as descending: Purposely (your conscious goal) → Knowingly (aware it will happen) → Recklessly (conscious disregard of risk) → Negligently (should have known the risk). Higher mens rea = harsher punishment.
Purposely
Conscious object to engage in the conduct or cause the result. The most culpable level — "I meant to do it."
Knowingly
Aware that the conduct is of that nature or that the result is practically certain to follow. "I knew it would happen."
Recklessly
Consciously disregards a substantial and unjustifiable risk. "I knew there was a serious risk and ignored it."
Negligently
Should have been aware of a substantial risk but wasn't. Objective standard — "a reasonable person would have known."
Homicide is the killing of one human by another — not all are criminal, and criminal homicides vary widely in severity. 1st degree murder requires premeditation + deliberation. 2nd degree is intentional but unplanned. Voluntary manslaughter is heat of passion. Involuntary is reckless or negligent killing.
Murder 1st degree
Premeditated + deliberate killing. "I planned it." Also includes felony murder during specified dangerous felonies (BARRK: Burglary, Arson, Rape, Robbery, Kidnapping).
Murder 2nd degree
Intentional killing without premeditation, or killing with extreme recklessness (depraved heart). Unplanned but intentional.
Voluntary manslaughter
Heat of passion killing — adequate provocation, no cooling-off period, causal link between provocation and killing.
Involuntary manslaughter
Reckless or criminally negligent killing — no intent to kill. DUI death is a common example.
Theft crimes look similar but have critical distinctions examiners love to test. LEFT·B·R: Larceny (trespassory taking) · Embezzlement (lawful possession then convert) · False pretenses (title through fraud) · Theft by trick (possession through fraud) · Burglary (breaking and entering) · Robbery (larceny + force or fear).
Larceny
Trespassory taking and carrying away of another's personal property with intent to permanently deprive. The baseline theft offense.
Embezzlement
Fraudulent conversion of property by someone who lawfully possessed it — e.g., an employee stealing from the register.
False pretenses
Obtaining title to property through a false representation of a material past or present fact. Victim passes title voluntarily.
Robbery
Larceny + force or intimidation from the victim's person or presence. Aggravated robbery involves a deadly weapon.
Burglary
Common law: breaking and entering a dwelling of another at nighttime with intent to commit a felony inside. Modern statutes broader.
SIDED covers the defenses most tested in criminal law. Some are complete defenses (acquittal) while others only reduce the charge or sentence. Self-defense and duress are justifications — the act was right. Insanity and diminished capacity are excuses — the act was wrong but defendant lacked culpability.
Self-defense
Reasonable belief of imminent unlawful force. Must use proportionate force. Initial aggressors generally cannot claim self-defense.
Insanity
M'Naghten: didn't know nature of act OR didn't know it was wrong. MPC: lacked substantial capacity to appreciate criminality or conform conduct.
Duress
Imminent threat of death or serious bodily harm compelling the crime. NOT a defense to murder in most jurisdictions.
Entrapment
Government induced a crime the defendant was not predisposed to commit. Subjective test (predisposition) vs. objective test (police conduct).
Diminished capacity
Mental impairment negates specific intent — reduces murder to manslaughter. Not a full defense; recognized in about half of states.
Inchoate Crimes
ACS
Attempt · Conspiracy · Solicitation
Incomplete Crimes — Punished Before the Act
Inchoate crimes punish steps toward a crime even if the target offense never occurs. ACS: Attempt (substantial step toward commission) · Conspiracy (agreement between two+ to commit a crime) · Solicitation (asking another to commit a crime). All three require mens rea — you must intend the target offense.
Attempt
Specific intent + a substantial step beyond mere preparation. MPC: substantial step strongly corroborative of criminal purpose. Abandonment is a defense under MPC only.
Conspiracy
Agreement between two or more persons to commit a crime + an overt act (MPC/most states). Pinkerton rule: co-conspirators liable for foreseeable crimes of each other.
Solicitation
Asking, encouraging, or inducing another to commit a crime with intent they do so. Complete at the moment of asking — no acceptance needed.
Merger
Attempt and solicitation merge into the completed crime if it occurs — can't be convicted of both. Conspiracy does NOT merge.
4th & 5th Amendment
MIRANDA = Must Inform Rights Before Any Questioning
Must · Inform · Rights · Before · Any · Questioning
Miranda Rights — When & What
Miranda warnings are required before custodial interrogation. MIRANDA: police Must Inform you of your Rights Before Any Questioning while in custody. The four warnings: right to remain silent · anything said can be used against you · right to an attorney · if you can't afford one, one will be appointed.
Custody
Person is deprived of freedom in a significant way — under arrest or equivalent restraint. Traffic stops alone are NOT custody.
Interrogation
Express questioning OR words/actions police should know are reasonably likely to elicit an incriminating response.
Waiver
Rights can be waived if waiver is knowing, voluntary, and intelligent. Silence alone is NOT a waiver — must be affirmative.
Consequence of violation
Statements obtained without Miranda warning are inadmissible in the prosecution's case-in-chief. Physical evidence derived may still be admissible (US v. Patane).
Accomplice Liability
PAPA
Principal · Aider · Principal in 2nd degree · Accessory after the fact
Who Is Liable — Parties to a Crime
Criminal liability extends beyond the person who pulls the trigger. PAPA: Principal (commits the act) · Aider and abettor (assists with intent) · Principal in 2nd degree (present, aids at the scene) · Accessory after the fact (helps after crime is complete — lesser offense). Modern law largely collapses these into principal and accomplice.
Accomplice liability
Aider/abettor is liable as a principal — same crime, same punishment. Must have intent to assist AND intent the crime be committed.
Mere presence
Simply being at the scene is NOT enough for accomplice liability. Must actively aid, abet, counsel, or encourage.
Accessory after the fact
Knowingly helps a felon escape arrest, trial, or punishment after the crime. Separate, lesser offense — not liable for the underlying crime.
Withdrawal
Accomplice can withdraw before the crime is committed by repudiating prior aid, notifying police, or neutralizing prior assistance.
Felony Murder
BARRK
Burglary · Arson · Rape · Robbery · Kidnapping
Felony Murder Rule — The 5 Triggering Felonies
The felony murder rule holds all participants liable for murder if anyone dies during the commission of a dangerous felony — even accidentally. BARRK covers the five felonies that most commonly trigger the rule. If a getaway driver's accomplice kills someone inside the bank, the driver is guilty of murder too.
The rule
No separate mens rea needed for the killing — the intent to commit the underlying felony substitutes. Strict liability for the death.
Scope
Applies to all co-felons present. Death of a co-felon by a victim or police typically does NOT trigger felony murder (agency theory).
Merger limitation
Underlying felony must be independent of the killing — assault cannot merge into felony murder or every assault killing becomes 1st degree murder.
Defenses
Abandonment before death occurs · Unanticipated act of co-felon in some jurisdictions · Victim was a co-felon (most states).