THE MISTAKEN LAW OF MISTAKES OF LAW:
MISTAKES NEGATING CULPABILITY UNDER THE MODEL
PENAL CODE
Scott England*
ABSTRACT
This Article examines the relationship between two core principles of American
criminal law. On one hand, ignorance of the law is no excuse. On the other hand,
criminal liability requires not just a guilty act but also a guilty mind. As the crimi-
nal law has become more complex, criminal offenses have increasingly raised
issues about whether they require culpability as to issues of law, often bringing
culpability requirements and the ignorance maxim into apparent conflict.
In 1962, the American Law Institute published the Model Penal Code (“MPC”
or “the Code”). The MPC changed American criminal law significantly, and the
Code’s culpability provisions are commonly recognized as the project’s greatest
contribution to American law. The Code includes a version of the ignorance maxim,
under which a defendant need not be culpable as to whether conduct constitutes an
offense. Importantly, however, the Code requires culpability for each element of an
offense, and the drafters recognized that offense elements can raise legal issues
about laws other than offenses themselves. Hence, the Code requires culpability for
countless collateral issues of law that arise under modern statutes, including
offenses that require one to violate a civil statute or court order, fail to perform a
legal duty, or engage in certain conduct after being convicted of a felony.
Unfortunately, the overwhelming majority of MPC states have undermined the
Code’s norm of requiring culpability for offense elements that raise collateral issues
of law. Many MPC states decline to exculpate for mistakes of law that negate culpa-
bility requirements, and courts often impose strict liability because they confuse mis-
takes as to offense elements with mistakes about criminality. As a result, MPC states
have thwarted some of the Code’s most important provisions. This Article concludes
by recommending ways to prevent strict liability for issues of law in MPC states.
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
I. HISTORIC BACKGROUND: MISTAKES OF LAW UNDER ROMAN LAW AND THE
COMMON LAW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
A. Roman Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
* Professor of Law & Regents’ Lecturer, University of New Mexico School of Law. I thank my wife, Heather
Mechler, for her support and encouragement. I also thank my colleagues Dean Camille Carey, George Bach,
Christy DeSanctis, Steven Homer, John Kang, Joshua Kastenberg, Nathalie Martin, Serge Martinez, Jennifer
Moore, Sergio Pareja, and David Stout. My work was supported by a summer research grant from the University
of New Mexico School of Law, for which I am grateful. © 2024, Scott England.
203
B. English Common Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
C. American Common Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
II. MISTAKES OF LAW UNDER THE MODEL PENAL CODE . . . . . . . . . . . . . . 212
A. Requiring Culpability for Collateral Issues of Law . . . . . . . . . 213
1. Overview of the Code’s Culpability Rules . . . . . . . . . . . . 213
2. Material Elements Include Collateral Issues of Law . . . . . 215
B. Mistakes of Law Negating Culpability . . . . . . . . . . . . . . . . . . 219
C. Mistakes about Criminality . . . . . . . . . . . . . . . . . . . . . . . . . . 223
D. Reasons for Requiring Culpability for Collateral Issues of Law 227
III. PROBLEMS WITH MISTAKES OF LAW IN MODEL PENAL CODE STATES . . . . 229
A. Failing to Require Culpability for Issues of Law. . . . . . . . . . . 232
1. Problems with Stated Culpability Requirements . . . . . . . . 232
2. Problems with Default Culpability Requirements . . . . . . . 235
B. Ignoring the Relationship Between Mistakes and Culpability
Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
C. Confusing Mistakes as to Elements with Mistakes about
Criminality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
IV. AVOIDING MISTAKES ABOUT MISTAKES OF LAW . . . . . . . . . . . . . . . . . . 244
A. Starting with Culpability Requirements . . . . . . . . . . . . . . . . . 245
B. Resolving Apparent Ambiguity about Mistakes of Law . . . . . . 246
C. Limiting the Ignorance Maxim to Mistakes about Criminality . 248
CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
INTRODUCTION
This Article examines the relationship between two of the most revered princi-
ples in criminal law. On one hand, ignorance of the law is no excuse.
1
Put differ-
ently, the criminal law generally provides no defense for even a reasonable
mistake about criminality—that is, “the meaning or existence of the criminal law
itself.”
2
On the other hand, it is an equally hallowed principle that criminal liability
1. JOSHUA DRESSLER, UNDERSTANDING CRIMINAL LAW § 13.01(A) (9th ed. 2022) (observing that the
ignorance maxim “is deeply embedded in Anglo-American jurisprudence”); Sharon L. Davies, The
Jurisprudence of Willfulness: An Evolving Theory of Excusable Ignorance, 48 DUKE L.J. 341, 342 (1998)
(“The principle of ignorantia legis non excusat—ignorance of the law does not excuse—is perhaps the most
well-rooted maxim in Anglo-American criminal law.”); Paul J. Larkin Jr., Taking Mistakes Seriously, 28
BYU J. PUB. L. 71, 75 (2013) (“The proposition that ignorance or mistake of the law is no excuse to a crime is
as firmly settled a legal doctrine as any rule could hope to be.”).
2. Larry Alexander, Inculpatory and Exculpatory Mistakes and the Fact/Law Distinction: An Essay in
Memory of Myke Balyes, 12 L. & PHIL. 33, 34 (1993); see also DRESSLER, supra note 1, § 13.01(A) (“[N]either
knowledge nor recklessness or negligence as to whether conduct constitutes an offense, or as to its meaning,
ordinarily is an element of that offense; therefore, it follows that there typically is no mens rea element in an
offense capable of being negated by an actor’s ignorance or mistake of law.”). A mistake of law technically
differs from ignorance of the law because a mistake requires some awareness of a law’s existence. Davies, supra
note 1, at 344 n.9; see Edwin R. Keedy, Ignorance and Mistake in the Criminal Law, 22 HARV. L. REV. 75, 76
(1908); Rollin M. Perkins, Ignorance and Mistake in Criminal Law, 88 U. PA. L. REV. 35, 35 (1939).
Nevertheless, most courts and commentators use the terms interchangeably when discussing the ignorance
204 AMERICAN CRIMINAL LAW REVIEW [Vol. 61:203
requires not just a guilty act but also a guilty mind.
3
Hence, the criminal law ordi-
narily frowns upon strict liability because it punishes those who lack the blame-
worthiness required for the law’s formal condemnation.
4
As applied to modern American criminal law, both principles have roots in
English common law dating back to the High Middle Ages.
5
For centuries, the ig-
norance maxim—ignorantia legis non excusat
6
—peacefully coexisted with culpa-
bility requirements. Such harmony was possible because the criminal law, like
society, was once far simpler than it is now. Indeed, English common law tradi-
tionally recognized just nine felonies: murder, manslaughter, rape, sodomy, bur-
glary, robbery, larceny, arson, and mayhem.
7
Additionally, the common law
simply required mens rea, a state of mind that varied little between offenses and
demanded only a “vicious will” or an “intention to commit a crime.”
8
Given the
law’s simplicity, the ignorance maxim made some sense, grounded as it was in the
rationale that the law was “definite and knowable.”
9
People were presumed to
know the law’s commands,
10
and thus the common law refused to provide a gen-
eral defense for mistakes of law.
11
maxim. See Vera Bolga
´r, The Present Function of the Maxim Ignorantia Iuris Neminem Excusat—A
Comparative Study, 52 IOWA L. REV. 626, 636 (1967); Davies, supra note 1, at 344 n.9; Keedy, supra, at 76;
Perkins, supra, at 35. This Article generally adopts that practice.
3. DRESSLER, supra note 1, § 9.01(A); WAYNE R. LAFAVE, SUBSTANTIVE CRIMINAL LAW § 5.1 (3d ed. 2017);
Ian P. Farrell & Justin F. Marceau, Taking Voluntariness Seriously, 54 B.C. L. REV. 1545, 1548–49 (2013);
Rollin M. Perkins, A Rationale of Mens Rea, 52 HARV. L. REV. 905, 908 (1939).
4. Herbert L. Packer, Mens Rea and the Supreme Court, 1962 SUP. CT. REV. 107, 147–48 (1962) (“Few today
cavil at strict liability in tort . . . . But the transfer of money from one pocket to another is one thing, and the
judgment of community condemnation expressed in a criminal conviction is quite another. So long as that
sanction is resorted to, moral blameworthiness should be the indispensable condition precedent to its
application.”); Francis Bowes Sayre, Public Welfare Offenses, 33 COLUM. L. REV. 55, 72 (1933) (“To subject
defendants entirely free from moral blameworthiness to the possibility of prison sentences is revolting to the
community sense of justice; and no law which violates this fundamental instinct can long endure. Crimes
punishable with prison sentences, therefore, ordinarily require proof of a guilty intent.”).
5. English courts began applying the ignorance maxim in criminal cases as early as the eleventh century. Davies,
supra note 1, at 351 n.47. According to the most popular account, English common law likely began requiring
culpability around the middle of the thirteenth century. Martin R. Gardner, The Mens Rea Enigma: Observations on
the Role of Motive in the Criminal Law Past and Present, 1993 UTAH L. REV. 635, 655 (1993); see Laurie L.
Levenson, Good Faith Defenses: Reshaping Strict Liability Crimes, 78 CORNELL L. REV. 401, 435–36 (1993).
6. Translated to English, this version of the ignorance maxim states that “ignorance of the law does not
excuse.” There are several other Latin versions of the ignorance maxim. Others include “ignorantia legis
neminem excusat”; “ignorantia eorum, quae quis scire tenetur, non excusat”; “ignorantia juris, quod quisque
tenetur scire, neminem excusat”; and “ignorantia juris haud excusat.” Keedy, supra note 2, at 76 n.1.
7. Alice Ristroph, Farewell to the Felonry, 53 HARV. C.R.-C.L. L. REV. 563, 572 (2018); Will Tress,
Unintended Collateral Consequences: Defining Felony in the Early American Republic, 57 CLEV. STATE L. REV.
461, 464 (2009).
8. Scott England, Default Culpability Requirements: The Model Penal Code and Beyond, 99 OR. L. REV. 43,
44 (2020).
9. DRESSLER, supra note 1, § 13.01(B)(1); Davies, supra note 1, at 352.
10. Bolga
´r, supra note 2, at 635; Davies, supra note 1, at 352; Jens David Ohlin, WHARTON’S CRIMINAL LAW
§ 13:3 (16th ed. 2021).
11. Livingston Hall & Selig J. Seligman, Mistake of Law and Mens Rea, 8 U. CHI. L. REV. 641, 644 (1941).
Commentators have offered additional rationales for the ignorance maxim. For example, Oliver Wendell Holmes
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