(Slip Opinion) OCTOBER TERM, 2014 1 

Syllabus 

NOTE: Where it is feasible, a syllabus (headnote) will be released, as is

being done in connection with this case, at the time the opinion is issued.

The syllabus constitutes no part of the opinion of the Court but has been

prepared by the Reporter of Decisions for the convenience of the reader. 

See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337. 

SUPREME COURT OF THE UNITED STATES 

Syllabus 

MCFADDEN v. UNITED STATES 

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR 

THE FOURTH CIRCUIT 

No. 14–378. Argued April 21, 2015—Decided June 18, 2015 

Petitioner McFadden was arrested and charged with distributing controlled substance analogues in violation of the federal Controlled

Substance Analogue Enforcement Act of 1986 (Analogue Act), which

identifies a category of substances substantially similar to those

listed on the federal controlled substances schedules, 21 U. S. C. 

§802(32)(A), and instructs courts to treat those analogues as schedule

I controlled substances if they are intended for human consumption,

§813. Arguing that he did not know the “bath salts” he was distributing were regulated as controlled substance analogues, McFadden

sought an instruction that would have prevented the jury from finding him guilty unless it found that he knew the substances he distributed had chemical structures and effects on the central nervous 

system substantially similar to those of controlled substances. Instead, the District Court instructed the jury that it need only find 

that McFadden knowingly and intentionally distributed a substance

with substantially similar effects on the central nervous system as a 

controlled substance and that he intended that substance to be consumed by humans. McFadden was convicted. The Fourth Circuit affirmed, holding that the Analogue Act’s intent element required only 

proof that McFadden intended the substance to be consumed by humans. 

Held: When a controlled substance is an analogue, §841(a)(1) requires

the Government to establish that the defendant knew he was dealing

with a substance regulated under the Controlled Substances Act or

Analogue Act. Pp. 4–11.

(a) In addressing the treatment of controlled substance analogues 

under federal law, one must look to the CSA, which, as relevant here, 

makes it “unlawful for any person knowingly . . . to distribute . . . a 
 

2 MCFADDEN v. UNITED STATES 

Syllabus 

controlled substance.” §841(a)(1). The ordinary meaning of that provision requires a defendant to know only that the substance he is distributing is some unspecified substance listed on the federal drug 

schedules. Thus, the Government must show either that the defendant knew he was distributing a substance listed on the schedules,

even if he did not know which substance it was, or that the defendant 

knew the identity of the substance he was distributing, even if he did

not know it was listed on the schedules. 

Because the Analogue Act extends that framework to analogous 

substances, the CSA’s mental-state requirement applies when the

controlled substance is, in fact, an analogue. It follows that the Government must prove that a defendant knew that the substance he 

was distributing was “a controlled substance,” even in prosecutions 

dealing with analogues. That knowledge requirement can be established in two ways: by evidence that a defendant knew that the substance he was distributing is controlled under the CSA or Analogue

Act, regardless of whether he knew the substance’s identity; or by evidence that the defendant knew the specific analogue he was distributing, even if he did not know its legal status as a controlled substance analogue. A defendant with knowledge of the features 

defining a substance as a controlled substance analogue, §802(32)(A),

knows all of the facts that make his conduct illegal. Pp. 4–8.

(b) The Fourth Circuit did not adhere to §813’s command to treat a

controlled substance analogue as a controlled substance listed in

schedule I by applying §841(a)(1)’s mental-state requirement. Instead, it concluded that the only mental-state requirement for analogue prosecutions is the one in §813—that an analogue be “intended

for human consumption.” That conclusion is inconsistent with the 

text and structure of the statutes. 

Neither the Government’s nor McFadden’s interpretation fares any 

better. The Government’s contention that §841(a)(1)’s knowledge requirement as applied to analogues is satisfied if the defendant knew 

he was dealing with a substance regulated under some law ignores 

§841(a)(1)’s requirement that a defendant know he was dealing with

“a controlled substance.” That term includes only drugs listed on the

federal drug schedules or treated as such by operation of the Analogue Act; it is not broad enough to include all substances regulated 

by any law. McFadden contends that a defendant must also know 

the substance’s features that cause it to fall within the scope of the

Analogue Act. But the key fact that brings a substance within the 

scope of the Analogue Act is that the substance is “controlled,” and

that fact can be established in the two ways previously identified. 

Staples v. United States, 511 U. S. 600, distinguished. Contrary to 

McFadden’s submission, the canon of constitutional avoidance “has 
Cite as: 576 U. S. ____ (2015) 3 

Syllabus 

no application” in the interpretation of an unambiguous statute such

as this one. Warger v. Shauers, 574 U. S. ___, ___. But even if the 

statute were ambiguous, the scienter requirement adopted here “alleviate[s] vagueness concerns” under this Court’s precedents. Gonzales v. Carhart, 550 U. S. 124, 149. Pp. 8–10. 

(c) The Government argues that no rational jury could have concluded that McFadden was unaware that the substances he was distributing were controlled under the CSA or Analogue Act and that

any error in the jury instruction was therefore harmless. The Fourth 

Circuit, which did not conduct a harmless-error analysis, is to consider that issue in the first instance. Pp. 10–11. 

753 F. 3d 432, vacated and remanded. 

THOMAS, J., delivered the opinion of the Court, in which SCALIA, 

KENNEDY, GINSBURG, BREYER, ALITO, SOTOMAYOR, and KAGAN, JJ., 

joined. ROBERTS, C. J., filed an opinion concurring in part and concurring in the judgment. 
 

 

_________________ 

_________________ 

 

Cite as: 576 U. S. ____ (2015) 1 

Opinion of the Court 

NOTICE: This opinion is subject to formal revision before publication in the

preliminary print of the United States Reports. Readers are requested to

notify the Reporter of Decisions, Supreme Court of the United States, Washington, D. C. 20543, of any typographical or other formal errors, in order

that corrections may be made before the preliminary print goes to press. 

SUPREME COURT OF THE UNITED STATES 

No. 14–378 

STEPHEN DOMINICK MCFADDEN, PETITIONER v.
 

UNITED STATES
 

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

APPEALS FOR THE FOURTH CIRCUIT
 

[June 18, 2015] 

JUSTICE THOMAS delivered the opinion of the Court. 

The Controlled Substance Analogue Enforcement Act of

1986 (Analogue Act) identifies a category of substances 

substantially similar to those listed on the federal controlled substance schedules, 21 U. S. C. §802(32)(A), and 

then instructs courts to treat those analogues, if intended

for human consumption, as controlled substances listed on 

schedule I for purposes of federal law, §813. The Controlled Substances Act (CSA) in turn makes it unlawful 

knowingly to manufacture, distribute, or possess with

intent to distribute controlled substances. §841(a)(1). The 

question presented in this case concerns the knowledge 

necessary for conviction under §841(a)(1) when the controlled substance at issue is in fact an analogue. 

We hold that §841(a)(1) requires the Government to

establish that the defendant knew he was dealing with “a

controlled substance.” When the substance is an analogue, that knowledge requirement is met if the defendant 

knew that the substance was controlled under the CSA or 

the Analogue Act, even if he did not know its identity. The 

knowledge requirement is also met if the defendant knew 
 

2 MCFADDEN v. UNITED STATES 

Opinion of the Court 

the specific features of the substance that make it a “‘controlled substance analogue.’” §802(32)(A). Because the 

U. S. Court of Appeals for the Fourth Circuit approved a 

jury instruction that did not accurately convey this

knowledge requirement, we vacate its judgment and remand for that court to determine whether the error was 

harmless. 

I 

In 2011, law enforcement officials in Charlottesville, 

Virginia, began investigating individuals at a Charlottesville video store for suspected distribution of “bath 

salts”—various recreational drugs used to produce effects 

similar to those of cocaine, methamphetamine, and other 

controlled substances. The owner of the store, Lois 

McDaniel, had been purchasing bath salts from petitioner

Stephen McFadden for several months. McFadden had 

marketed the substances to her as “Alpha,” “No Speed,” 

“Speed,” “Up,” and “The New Up,” and had compared them

to cocaine and crystal meth. He had often sold those 

products with labels borrowing language from the Analogue Act, asserting that the contents were “not for human

consumption” or stating that a particular product “does 

not contain any of the following compounds or analogues

of the following compounds” and listing controlled substances. McDaniel purchased the bath salts for $15 per

gram and resold them for $30 to $70 per gram. 

After investigators had conducted two controlled buys 

from the store and confronted McDaniel, she agreed to

cooperate in their investigation by making five controlled 

buys from McFadden. The Government intercepted the 

substances McFadden sent when they arrived at the local

FedEx store. Like the substances sold in the video store, 

these substances were white and off-white powders packaged in small plastic bags. Chemical analysis identified

the powders as containing, among other substances, 3,4-
 

Cite as: 576 U. S. ____ (2015) 3 

Opinion of the Court 

Methylenedioxypyrovalerone, also known as MDPV; 3,4-

Methylenedioxy-N-methylcathinone, also known as Methylone or MDMC; and 4-Methyl-N-ethylcathinone, also

known as 4-MEC. When ingested, each of these substances is capable of producing effects on the central

nervous system similar to those that controlled substances

(such as cocaine, methamphetamine, and methcathinone) 

produce.

A federal grand jury indicted McFadden on eight counts

of distribution of controlled substance analogues and one

count of conspiracy. At trial, McFadden argued that he 

did not know the substances he was distributing were 

regulated as controlled substances under the Analogue 

Act. He and the Government also disagreed about what

knowledge was required for a conviction. The Government 

sought an instruction requiring only “[t]hat the defendant 

knowingly and intentionally distributed a mixture or 

substance . . . [t]hat . . . was a controlled substance analogue . . . with the intent that it be consumed by humans.” 

App. 26–27. McFadden sought a more demanding instruction requiring that he “knew that the substances that he

was distributing possessed the characteristics of controlled

substance analogues,” including their chemical structures

and effects on the central nervous system. Id., at 29–30. 

The District Court compromised, instructing the jury that

the statute required that “the defendant knowingly and 

intentionally distributed a mixture or substance that has” 

substantially similar effects on the nervous system as a

controlled substance and “[t]hat the defendant intended 

for the mixture or substance to be consumed by humans.” 

Id., at 40. 

The jury convicted McFadden on all nine counts. On 

appeal, McFadden insisted that the District Court “erred

in refusing to instruct the jury that the government was 

required to prove that he knew, had a strong suspicion, or 

deliberately avoided knowledge that the [substances] 
 

 

 

4 MCFADDEN v. UNITED STATES 

Opinion of the Court 

possessed the characteristics of controlled substance analogues.” 753 F. 3d 432, 443 (CA4 2014). Rejecting that 

argument, the Court of Appeals affirmed. Id., at 444, 446. 

Stating that it was bound by Circuit precedent, the court

concluded that the “intent element [in the Act] requires 

[only] that the government prove that the defendant 

meant for the substance at issue to be consumed by humans.” Id., at 441; see id., at 444. 

We granted a writ of certiorari, 574 U. S ___ (2015), and 

now vacate the judgment of the Court of Appeals and 

remand. 

II
 

A 

The Analogue Act requires a controlled substance analogue, if intended for human consumption, to be treated 

“as a controlled substance in schedule I” for purposes of 

federal law. §1201, 100 Stat. 3207–13, 21 U. S. C. §813.

We therefore must turn first to the statute that addresses 

controlled substances, the CSA. The CSA makes it “unlawful for any person knowingly or intentionally . . . to 

manufacture, distribute, or dispense, or possess with

intent to manufacture, distribute, or dispense, a controlled 

substance.” §401(a)(1), 84 Stat. 1260, 21 U. S. C. 

§841(a)(1). Under the most natural reading of this provision, the word “knowingly” applies not just to the statute’s 

verbs but also to the object of those verbs—“a controlled 

substance.” See Flores-Figueroa v. United States, 556 

U. S. 646, 650 (2009); id., at 657 (SCALIA, J., concurring in 

part and concurring in judgment); id., at 660–661 (ALITO, 

J., concurring in part and concurring in judgment). When 

used as an indefinite article, “a” means “[s]ome undetermined or unspecified particular.” Webster’s New International Dictionary 1 (2d ed. 1954). And the CSA defines 

“controlled substance” as “a drug or other substance, or

immediate precursor, included in schedule I, II, III, IV, or 
 

Cite as: 576 U. S. ____ (2015) 5 

Opinion of the Court 

V.” §802(6) (internal quotation marks omitted). The 

ordinary meaning of §841(a)(1) thus requires a defendant 

to know only that the substance he is dealing with is some

unspecified substance listed on the federal drug schedules.

The Courts of Appeals have recognized as much. See, e.g., 

United States v. Andino, 627 F. 3d 41, 45–46 (CA2 2010); 

United States v. Gamez-Gonzalez, 319 F. 3d 695, 699 (CA5 

2003); United States v. Martinez, 301 F. 3d 860, 865 (CA7 

2002).

That knowledge requirement may be met by showing 

that the defendant knew he possessed a substance listed 

on the schedules, even if he did not know which substance 

it was. Take, for example, a defendant whose role in a 

larger drug organization is to distribute a white powder to 

customers. The defendant may know that the white powder is listed on the schedules even if he does not know 

precisely what substance it is. And if so, he would be 

guilty of knowingly distributing “a controlled substance.” 

The knowledge requirement may also be met by showing 

that the defendant knew the identity of the substance he 

possessed. Take, for example, a defendant who knows he

is distributing heroin but does not know that heroin is 

listed on the schedules, 21 CFR §1308.11 (2014). Because 

ignorance of the law is typically no defense to criminal

prosecution, Bryan v. United States, 524 U. S. 184, 196 

(1998), this defendant would also be guilty of knowingly 

distributing “a controlled substance.”1 

—————— 

1The Courts of Appeals have held that, as with most mens rea requirements, the Government can prove the requisite mental state

through either direct evidence or circumstantial evidence. Direct 

evidence could include, for example, past arrests that put a defendant

on notice of the controlled status of a substance. United States v. 

Abdulle, 564 F. 3d 119, 127 (CA2 2009). Circumstantial evidence could 

include, for example, a defendant’s concealment of his activities, evasive behavior with respect to law enforcement, knowledge that a 

particular substance produces a “high” similar to that produced by

controlled substances, and knowledge that a particular substance is 
 

 

6 MCFADDEN v. UNITED STATES 

Opinion of the Court 

The Analogue Act extends the framework of the CSA to

analogous substances. 21 U. S. C. §813. The Act defines a 

“controlled substance analogue” as a substance: 

“(i) the chemical structure of which is substantially

similar to the chemical structure of a controlled substance in schedule I or II; 

“(ii) which has a stimulant, depressant, or hallucinogenic effect on the central nervous system that is

substantially similar to or greater than the stimulant,

depressant, or hallucinogenic effect on the central 

nervous system of a controlled substance in schedule I 

or II; or 

“(iii) with respect to a particular person, which such 

person represents or intends to have a stimulant, depressant, or hallucinogenic effect on the central nervous system that is substantially similar to or greater 

than the stimulant, depressant, or hallucinogenic effect on the central nervous system of a controlled substance in schedule I or II.” §802(32)(A). 

It further provides, “A controlled substance analogue 

shall, to the extent intended for human consumption, be

treated, for the purposes of any Federal law as a controlled 

substance in schedule I.” §813.

The question in this case is how the mental state requirement under the CSA for knowingly manufacturing,

distributing, or possessing with intent to distribute “a 

controlled substance” applies when the controlled substance is in fact an analogue. The answer begins with 

§841(a)(1), which expressly requires the Government to 

prove that a defendant knew he was dealing with “a controlled substance.” The Analogue Act does not alter that

provision, but rather instructs courts to treat controlled 

—————— 

subject to seizure at customs. United States v. Ali, 735 F. 3d 176, 188– 

189 (CA4 2013). The Government presented such circumstantial 

evidence in this case, and neither party disputes that this was proper. 
 

Cite as: 576 U. S. ____ (2015) 7 

Opinion of the Court 

substance analogues “as . . . controlled substance[s] in 

schedule I.” §813. Applying this statutory command, it 

follows that the Government must prove that a defendant 

knew that the substance with which he was dealing was “a 

controlled substance,” even in prosecutions involving an 

analogue.2 

That knowledge requirement can be established in two 

ways. First, it can be established by evidence that a defendant knew that the substance with which he was dealing is some controlled substance—that is, one actually 

listed on the federal drug schedules or treated as such by

operation of the Analogue Act—regardless of whether he

knew the particular identity of the substance. Second, it 

can be established by evidence that the defendant knew

the specific analogue he was dealing with, even if he did

not know its legal status as an analogue. The Analogue

Act defines a controlled substance analogue by its features, as a substance “the chemical structure of which is 

substantially similar to the chemical structure of a controlled substance in schedule I or II”; “which has a stimulant, depressant, or hallucinogenic effect on the central

nervous system that is substantially similar to or greater 

than” the effect of a controlled substance in schedule I or 

II; or which is represented or intended to have that effect 

with respect to a particular person. §802(32)(A). A defendant who possesses a substance with knowledge of 

—————— 

2The Government has accepted for the purpose of this case that it 

must prove two elements to show that a substance is a controlled

substance analogue under the definition in §802(32)(A): First, that an

alleged analogue is substantially similar in chemical structure to a 

controlled substance, §802(32)(A)(i). Second, that an alleged analogue

either has, or is represented or intended to have, a stimulant, depressant, hallucinogenic effect on the central nervous system that is substantially similar to that of a controlled substance, §§802(32)(A)(ii), (iii).

Brief for United States 3. Because we need not decide in this case 

whether that interpretation is correct, we assume for the sake of 

argument that it is. 
 

 

8 MCFADDEN v. UNITED STATES 

Opinion of the Court 

those features knows all of the facts that make his conduct 

illegal, just as a defendant who knows he possesses heroin

knows all of the facts that make his conduct illegal. A 

defendant need not know of the existence of the Analogue 

Act to know that he was dealing with “a controlled 

substance.” 

B 

The Court of Appeals did not adhere to §813’s command 

to treat a controlled substance analogue “as a controlled 

substance in schedule I,” and, accordingly, it did not apply 

the mental-state requirement in §841(a)(1). Instead, it 

concluded that the only mental state requirement for

prosecutions involving controlled substance analogues is

the one in §813—that the analogues be “intended for 

human consumption.” 753 F. 3d, at 436 (citing United 

States v. Klecker, 348 F. 3d 69, 71 (CA4 2003)). Because 

that interpretation is inconsistent with the text and structure of the statutes, we decline to adopt it. 

Unsurprisingly, neither the Government nor McFadden

defends the Court of Appeals’ position. But their alternative interpretations fare no better. The Government 

agrees that the knowledge requirement in §841(a)(1) 

applies to prosecutions involving controlled substance 

analogues, yet contends that it is met if the “defendant 

knew he was dealing with an illegal or regulated substance” under some law. Brief for United States 15. 

Section 841(a)(1), however, requires that a defendant 

knew he was dealing with “a controlled substance.” That 

term includes only those drugs listed on the federal drug 

schedules or treated as such by operation of the Analogue 

Act. §§802(6), 813. It is not broad enough to include all 

substances regulated by any law.3 

—————— 

3Although the Government must prove that a defendant knew that

the substance in question was “a controlled substance” under federal 

law, the Government need not introduce direct evidence of such 
 

 

Cite as: 576 U. S. ____ (2015) 9 

Opinion of the Court 

For his part, McFadden contends that, in the context of 

analogues, knowledge of “a controlled substance” can only

be established by knowledge of the characteristics that

make a substance an “analogue” under the Act. In support of that argument, he relies heavily on our conclusion 

in Staples v. United States, 511 U. S. 600 (1994), that a 

statute making it “‘unlawful for any person . . . to receive 

or possess a firearm which is not registered to him in the 

National Firearms Registration and Transfer Record,’” id., 

at 605 (quoting 26 U. S. C. §5861(d)), required proof that a

defendant “knew of the features of his AR–15 that brought 

it within the scope of the Act,” 511 U. S., at 619. McFadden reasons by analogy that a defendant convicted under

§841(a)(1) must also know the features of the substance

that brought it within the scope of the Analogue Act. But 

that position ignores an important textual distinction

between §841(a)(1) and the statute at issue in Staples. 

The statute at issue in Staples defined “a firearm” by its 

physical features such as the length of its barrel and its 

capacity to shoot more than one shot with a single function

of the trigger. Unlike those physical features that brought 

the firearm “within the scope of ” that statute, the feature of a substance “that br[ings] it within the scope of” 

§841(a)(1) is the fact that it is “‘controlled.’” §802(6).

Knowledge of that fact can be established in the two 

ways previously discussed: either by knowledge that a 

substance is listed or treated as listed by operation of 

the Analogue Act, §§802(6), 813, or by knowledge of the 

physical characteristics that give rise to that treatment. 

—————— 

knowledge. As with prosecutions involving substances actually listed

on the drug schedules, the Government may offer circumstantial 

evidence of that knowledge. See n. 1, supra. In such cases, it will be 

left to the trier of fact to determine whether the circumstantial evidence proves that the defendant knew that the substance was a controlled substance under the CSA or Analogue Act, as opposed to under 

any other federal or state laws. 
 

 

10 MCFADDEN v. UNITED STATES 

Opinion of the Court 

Supra, at 7. 

McFadden also invokes the canon of constitutional 

avoidance, arguing that we must adopt his interpretation 

of the statute lest it be rendered unconstitutionally vague. 

But that argument fails on two grounds. Under our precedents, this canon “is a tool for choosing between competing plausible interpretations of a provision.” Warger v. 

Shauers, 574 U. S. ___, ___ (2014) (slip op., at 10) (internal 

quotation marks omitted). It “has no application” in the 

interpretation of an unambiguous statute such as this one.

See ibid. (internal quotation marks omitted). Even if this 

statute were ambiguous, McFadden’s argument would 

falter. Under our precedents, a scienter requirement in a 

statute “alleviate[s] vagueness concerns,” “narrow[s] the

scope of the [its] prohibition[,] and limit[s] prosecutorial 

discretion.” Gonzales v. Carhart, 550 U. S. 124, 149, 150 

(2007). The scienter requirement in this statute does not,

as McFadden suggests, render the statute vague. Moreover, to the extent McFadden suggests that the substantial 

similarity test for defining analogues is itself indeterminate, his proposed alternative scienter requirement would 

do nothing to cure that infirmity. 

III 

The District Court’s instructions to the jury did not fully

convey the mental state required by the Analogue Act. 

The jury was instructed only that McFadden had to

“knowingly and intentionally distribut[e] a mixture or 

substance that has an actual, intended, or claimed stimulant, depressant, or hallucinogenic effect on the central

nervous system” substantially similar to that of a controlled substance. App. 40. 

The Government contends that any error in the jury

instructions was harmless because no rational jury could

have concluded that McFadden was unaware that the 

substances he was distributing were controlled. We have 
 

Cite as: 576 U. S. ____ (2015) 11 

Opinion of the Court 

recognized that even the omission of an element from a 

jury charge is subject to harmless-error analysis. Neder v. 

United States, 527 U. S. 1, 15 (1999). Because the Court of 

Appeals did not address that issue, we remand for that

court to consider it in the first instance. 

* * * 

For the foregoing reasons, we vacate the judgment of the

Court of Appeals and remand the case for further proceedings consistent with this opinion. 

It is so ordered. 
 

_________________ 

_________________ 

 

Cite as: 576 U. S. ____ (2015) 1 

Opinion of ROBERTS, C. J. 

SUPREME COURT OF THE UNITED STATES 

No. 14–378 

STEPHEN DOMINICK MCFADDEN, PETITIONER v.
 

UNITED STATES
 

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

APPEALS FOR THE FOURTH CIRCUIT
 

[June 18, 2015] 

CHIEF JUSTICE ROBERTS, concurring in part and concurring in the judgment. 

I join the Court’s opinion, except to the extent that it

says the Government can satisfy the mental state requirement of Section 841(a)(1) “by showing that the defendant knew the identity of the substance he possessed.” 

Ante, at 5. Section 841(a)(1) makes it “unlawful for any 

person knowingly . . . to manufacture, distribute, or dispense . . . a controlled substance.” As the Court points out, 

the word “knowingly” applies “not just to the statute’s 

verbs, but also to the object of those verbs—‘a controlled 

substance.’” Ante, at 4 (emphasis deleted). That suggests

that a defendant needs to know more than the identity of 

the substance; he needs to know that the substance is 

controlled. See, e.g., United States v. Howard, 773 F. 3d 

519, 526 (CA4 2014); United States v. Washington, 596 

F. 3d 926, 944 (CA8 2010); United States v. Rogers, 387 

F. 3d 925, 935 (CA7 2004).

In cases involving well-known drugs such as heroin, a 

defendant’s knowledge of the identity of the substance can

be compelling evidence that he knows the substance is

controlled. See United States v. Turcotte, 405 F. 3d 515, 

525 (CA7 2005). But that is not necessarily true for lesser 

known drugs. A pop quiz for any reader who doubts the

point: Two drugs—dextromethorphan and hydrocodone— 
 

 

2 MCFADDEN v. UNITED STATES 

Opinion of ROBERTS, C. J. 

are both used as cough suppressants. They are also both 

used as recreational drugs. Which one is a controlled 

substance?* 

The Court says that knowledge of the substance’s identity suffices because “ignorance of the law is typically no

defense to criminal prosecution.” Ante, at 5. I agree that

is “typically” true. But when “there is a legal element in

the definition of the offense,” a person’s lack of knowledge 

regarding that legal element can be a defense. Liparota v. 

United States, 471 U. S. 419, 425, n. 9 (1985). And here, 

there is arguably a legal element in Section 841(a)(1)—

that the substance be “controlled.” 

The analogy the Court drew in Liparota was to a charge

of receipt of stolen property: It is no defense that the

defendant did not know such receipt was illegal, but it is a 

defense that he did not know the property was stolen. 

Here, the argument goes, it is no defense that a defendant 

did not know it was illegal to possess a controlled substance, but it is a defense that he did not know the substance was controlled. 

Ultimately, the Court’s statements on this issue are not

necessary to its conclusion that the District Court’s jury

instructions “did not fully convey the mental state required by the Analogue Act.” Ante, at 10. Those statements should therefore not be regarded as controlling if 

the issue arises in a future case. 

—————— 

* The answer is hydrocodone.