Study guide
8.4 Mistake of Fact, Mistake of Law & Concurrence
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1 Introduction & FYLSE Examination Guide
1.1 FYLSE Exam Structure, Passing Standard & Administration 1.2 Study Method, Pacing & MBE-Style Technique
2 Contracts: Mutual Assent, Capacity & Contract Formation
2.1 The Offer & Objective Theory of Assent 2.2 Termination & Irrevocability of Offers 2.3 Acceptance & the Mailbox Rule 2.4 Mirror Image Rule & UCC 2-207 Battle of the Forms 2.5 Mistake in Contract Formation 2.6 Fraud, Duress, Undue Influence & Illegality 2.7 Capacity to Contract
3 Contracts: Consideration, Estoppel & Implied Obligations
3.1 Consideration & the Bargained-For Exchange 3.2 Past & Moral Consideration, Pre-Existing Duty & Modification 3.3 Promissory Estoppel & Detrimental Reliance 3.4 Implied-in-Fact Contracts & Quasi-Contract 3.5 Implied Covenant of Good Faith, Fair Dealing & Indefinite Terms
4 Contracts: Third-Party Beneficiaries, Assignment & Delegation
4.1 Third-Party Beneficiary Contracts 4.2 Assignment of Rights 4.3 Delegation of Duties
5 Contracts: Statute of Frauds, Parol Evidence & Interpretation
5.1 Statute of Frauds: Contracts Within the Statute 5.2 Satisfying the Statute: Writing, Signature & Exceptions 5.3 The Parol Evidence Rule 5.4 Contract Interpretation & Canons of Construction
6 Contracts: Performance, Conditions, UCC Warranties & Breach
6.1 Conditions: Express, Constructive & Excuse 6.2 Substantial Performance vs. Perfect Tender 6.3 Cure, Rejection, Revocation & Installment Contracts 6.4 UCC Article 2 Warranties & Risk of Loss 6.5 Anticipatory Repudiation & Insecurity
7 Contracts: Remedies, Discharge & Changed Circumstances
7.1 Expectation Damages & Their Limitations 7.2 Reliance, Restitution & Liquidated Damages 7.3 Specific Performance & Injunctive Relief 7.4 UCC Article 2 Buyer's and Seller's Remedies 7.5 Impossibility, Impracticability & Frustration of Purpose 7.6 Discharge by Agreement: Rescission, Novation & Accord and Satisfaction
8 Criminal Law: Principles of Criminal Liability & Mens Rea
8.1 Actus Reus, Voluntary Acts & Omissions 8.2 Criminal Causation & Intervening Causes 8.3 Common Law & Model Penal Code Mens Rea 8.4 Mistake of Fact, Mistake of Law & Concurrence
9 Criminal Law: Inchoate Offenses & Accomplice Liability
9.1 Criminal Attempt & Impossibility 9.2 Solicitation & the Merger Doctrine 9.3 Conspiracy & Merger Doctrine 9.4 Accomplice Liability: Actus Reus & Mens Rea 9.5 Scope of Accomplice Liability, Withdrawal & Parties to Crime
10 Criminal Law: Homicide & Crimes Against the Person
10.1 Common Law Murder & Malice Aforethought 10.2 Degrees of Murder, Premeditation & Deliberation 10.3 The Felony Murder Rule & Its Limitations 10.4 Voluntary & Involuntary Manslaughter 10.5 Non-Homicide Crimes Against the Person
11 Criminal Law: Property Crimes, Theft & Habitation
11.1 Common Law Larceny 11.2 Embezzlement & False Pretenses 11.3 Robbery & Extortion 11.4 Receiving Stolen Property 11.5 Burglary 11.6 Arson
12 Criminal Law: Defenses: Capacity, Justification & Excuse
12.1 Insanity: The Four Legal Tests 12.2 Intoxication, Diminished Capacity & Infancy 12.3 Self-Defense & Defense of Others 12.4 Defense of Property, Habitation & Law Enforcement Privileges 12.5 Duress & Necessity 12.6 Entrapment & Mistake as an Excuse
13 Torts: Intentional Torts to Persons & Property
13.1 Intent, Motive & Incapacity in Intentional Torts 13.2 Transferred Intent 13.3 Battery & Assault 13.4 False Imprisonment 13.5 Trespass to Land 13.6 Trespass to Chattels & Conversion
14 Torts: Privileges & Defenses to Intentional Torts
14.1 Consent: Express, Implied & Capacity 14.2 Exceeding & Vitiating Consent 14.3 Self-Defense & Defense of Others (Tort) 14.4 Defense of Property & Recapture of Chattels 14.5 Public & Private Necessity 14.6 The Shopkeeper's Privilege
15 Torts: Negligence — Duty of Care & Breach
15.1 Duty of Care & the Foreseeable Plaintiff 15.2 Affirmative Duties to Act & Special Relationships 15.3 Standard of Care: The Reasonable Person & Children 15.4 Professional Negligence, Informed Consent & Negligence Per Se 15.5 Land Possessor Liability & Premises Duties 15.6 Breach of Duty & Res Ipsa Loquitur
16 Torts: Causation, Defenses, Multiple Tortfeasors, Wrongful Death & Damages
16.1 Cause in Fact & Multiple Actors 16.2 Proximate Cause & Intervening Forces 16.3 Contributory, Comparative Negligence & Assumption of Risk 16.4 Joint and Several Liability, Contribution & Indemnity 16.5 Vicarious Liability & Non-Delegable Duties 16.6 Wrongful Death & Survival Actions 16.7 Statute of Limitations & Claim Accrual 16.8 Tort Damages: Compensatory, Nominal, Punitive & Mitigation
17 Torts: Strict Liability & Products Liability
17.1 Strict Liability for Animals 17.2 Abnormally Dangerous Activities & Scope of Risk 17.3 Strict Products Liability & Defect Categories 17.4 Products Liability Under Negligence, Warranty & Misrepresentation 17.5 Defenses to Products Liability
18 Torts: Emotional Distress, Defamation, Privacy & Economic Torts
18.1 Intentional Infliction of Emotional Distress 18.2 Negligent Infliction of Emotional Distress 18.3 Common Law Defamation: Elements, Libel & Slander 18.4 Constitutional Limits, Privileges & Defenses to Defamation 18.5 Invasion of Privacy 18.6 Nuisance & Economic Torts
8.4 Mistake of Fact, Mistake of Law & Concurrence
Key Takeaways Explain This Topic AI
For a specific intent crime any honest mistake of fact negates intent, even if the mistake was unreasonable.
For a general intent or malice crime a mistake of fact must be both honest and objectively reasonable to excuse.
Mistake of fact is never a defense to a strict liability offense.
Ignorance of the law is generally no excuse, with narrow exceptions for reliance on an official statement of law later held invalid, lack of reasonable notice of the law, and mistakes negating a specific intent element.
Concurrence requires that the mens rea actually prompt the actus reus, so forming the intent after the act is complete does not create liability.
Last updated: September 2026
- Mistake of Fact, Mistake of Law & Concurrence
- 1. Mistake of Fact: Specific Intent vs. General Intent
- The Doctrinal Mechanics
Mistake of fact is not an affirmative defense in the traditional sense; rather, it is a defense because it negates the mental state (mens rea) required for the commission of the charged crime. The validity of the defense depends strictly on the category of the offense: Does Mistake Negate Mens Rea?
- ├── Specific Intent Offense ──▶ ANY Honest Mistake (Reasonable OR Unreasonable) Excuses Liability
- ├── General Intent Offense ──▶ ONLY an Honest AND REASONABLE Mistake Excuses Liability
- ├── Malice Offense ──▶ ONLY an Honest AND REASONABLE Mistake Excuses Liability
- └── Strict Liability ──▶ NEVER a Defense (Mistake of Fact Completely Irrelevant)
- The FYLSE "Claim of Right" Trap in Theft Crimes
Larceny requires the trespassory taking and carrying away of the personal property of another with the specific intent to permanently deprive the owner thereof ( animus furandi ). If a defendant takes an item under an honest, good-faith belief that the property belongs to them, or that they have a legal right to take possession of it, the defendant lacks the specific intent to steal.
Exam Application: Even if the defendant's belief was completely foolish, irrational, or negligent (e.g., taking an umbrella that looks completely different from their own, or seizing a television from a debtor under the erroneous belief that self-help repossession without a court order is legal), the honest belief negates specific intent , barring a conviction for larceny or robbery.
- 2. Mistake of Law & The Advice of Counsel Trap
- The Baseline: Ignorantia Juris Non Excusat
The ancient common-law rule ignorantia juris non excusat (ignorance of the law is no excuse) remains a pillar of criminal jurisprudence. A defendant cannot avoid criminal liability by demonstrating that they were unaware that their conduct was prohibited by the penal code, or that they misunderstood the legal scope of a criminal statute, even if their ignorance was entirely reasonable and held in good faith.
The Three Narrow Recognized Exceptions
A mistake of law will excuse a defendant only under three highly specific, narrow exceptions:
Statute Not Published or Reasonably Made Available: Due process guarantees fair notice. If a penal statute or administrative regulation was not published, promulgated, or reasonably made available to the public prior to the defendant's conduct, prosecution is unconstitutional ( Lambert v. California , 355 U.S. 225 (1957)).
Reasonable Reliance on an Official Statement of Law: The defendant engaged in conduct in reasonable reliance upon an official, authoritative statement of the law afterward determined to be invalid or erroneous, contained in:
An official statute or judicial decision of the highest appellate court in the jurisdiction;
An official written interpretation issued by the public officer or administrative agency charged by law with enforcing or interpreting the statute (e.g., a formal written opinion issued by the State Attorney General).
Collateral Mistake of Law Negating Specific Mens Rea: Where the definition of a specific intent offense incorporates a non-penal legal standard, an honest mistake concerning that collateral civil law negates the specific intent required by the penal statute (e.g., a defendant who fails to file a tax return because of an honest, good-faith misunderstanding of complex federal tax regulations lacks the required "willfulness" for criminal tax evasion).
The Fatal FYLSE Trap: Reliance on Private Legal Counsel
Examiners constantly test examinees with fact patterns where a defendant consults a licensed, experienced private attorney, receives explicit formal written advice that a planned business operation is completely lawful under state criminal statutes, relies on that advice in good faith, and is subsequently arrested.
THE HARD RULE: Reliance on the advice of a private attorney is NEVER a valid defense of mistake of law . Private attorneys are not government officials, and their legal opinions do not constitute an official statement of the law. The defendant acts at their own peril.
- 3. The Concurrence Principle
- Temporal and Motivational Coincidence
To establish criminal guilt, the prosecution must prove the concurrence principle : the required mental state ( mens rea ) must actuate and coincide temporally with the physical conduct ( actus reus ). The mental state must be the moving force that triggers the physical act that causes the prohibited harm.
Recurring Concurrence Traps on the FYLSE
Antecedent Intent Abandoned Before the Act: A defendant forms a premeditated intent to murder their business rival, purchases a gun, but subsequently experiences remorse and abandons the murder plan entirely. Three weeks later, while driving safely and obeying all traffic laws, the defendant accidentally strikes a pedestrian who darted into traffic. The pedestrian is discovered to be the business rival. The defendant is not guilty of murder because the prior intent did not actuate or coincide with the accidental physical collision.
Subsequent Intent Formed After the Physical Act: A defendant accidentally backs his car out of a driveway and strikes a pedestrian, causing fatal head trauma. Upon exiting the vehicle, the defendant discovers that the deceased pedestrian is his bitter mortal enemy, and the defendant dances with joy and proclaims his happiness that the victim is dead. The defendant is not guilty of murder because the malicious intent arose after the physical actus reus had already occurred.
The Continuing Trespass Exception in Larceny: A narrow common-law exception exists for theft crimes under the doctrine of continuing trespass . If a defendant takes another's personal property without permission (a trespassory taking) but without an initial intent to steal (e.g., intending only to borrow the item temporarily), and later decides to keep the property permanently, the original trespassory taking is deemed to "continue" in the eyes of the law until the intent to permanently deprive is formed, thereby satisfying the concurrence requirement for common-law larceny.