(Slip Opinion)              OCTOBER TERM, 2009                                       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

                    UNITED STATES v. MARCUS

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
                 THE SECOND CIRCUIT

    No. 08–1341. Argued February 24, 2010—Decided May 24, 2010
Respondent Marcus was convicted of engaging in forced labor and sex
  trafficking between January 1999 and October 2001. On appeal, he
  pointed out for the first time that the federal statutes he violated did
  not become law until October 2000. Thus, he claimed, the indictment
  and evidence permitted at trial allowed a jury to convict him exclu
  sively on the basis of preenactment conduct in violation of the Ex Post
  Facto Clause. He conceded that he had not raised this objection in
  the District Court, but argued that because the constitutional error
  was plain, his conviction must be set aside. The Second Circuit
  agreed and vacated the conviction. In doing so, the court held that,
  even in the case of a continuing offense, retrial is necessary if there is
  “any possibility, no matter how unlikely, that the jury could have
  convicted based exclusively on pre-enactment conduct.” The court
  noted that this was “true even under plain error review.”
Held: The Second Circuit’s plain-error standard conflicts with this
 Court’s interpretation of the plain-error rule. An appellate court may
 recognize a “plain error that affects substantial rights,” even if that
 error was “not brought” to the district court’s “attention.” Fed. Rule
 Crim. Proc. 52(b). This Court’s cases interpret this rule such that an
 appellate court may, in its discretion, correct an error not raised at
 trial only when the appellant demonstrates that (1) there is an error;
 (2) the error is clear or obvious; (3) the error affected the appellant’s
 substantial rights; and (4) the error seriously affects the fairness, in
 tegrity, or public reputation of judicial proceedings.
    The standard the Second Circuit applied in this case is inconsistent
  with the third and fourth of these criteria. To begin, it is irreconcil
  able with the criterion that the error “affec[t] the appellant’s substan
2                     UNITED STATES v. MARCUS

                                  Syllabus

    tial rights,” Puckett v. United States, 556 U. S. ___, ___. This condi
    tion requires the error to be prejudicial, meaning that there is a rea
    sonable probability that the error affected the trial’s outcome, not
    that there is “any possibility,” however remote, that the jury could
    have convicted based exclusively on preenactment conduct.
       Nor does this error fall within the category of “structural errors”
    that may “affect substantial rights” regardless of their actual impact
    on an appellant’s trial. Id., at ___. Here, a jury instruction might
    have minimized or eliminated the risk that Marcus would have been
    convicted based solely on preenactment conduct. A reviewing court
    should find it no more difficult to assess the failure to give such an
    instruction than to assess numerous other instructional errors previ
    ously found nonstructural, see, e.g., Hedgpeth v. Pulido, 555 U. S. ___
    (per curiam). The Court further rejects Marcus’ argument that the
    error at issue should be labeled an Ex Post Facto Clause violation,
    and that all such violations should be treated as special, structural
    errors warranting reversal without a showing of prejudice. As an ini
    tial matter, the Government never argued that the statute that
    criminalized Marcus’ conduct applied retroactively, and Marcus’
    claim is thus properly brought under the Due Process, and not the
    Ex Post Facto, Clause. Moreover, we see no reason why errors simi
    lar to the one at issue in this case, taken as a class, would automati
    cally affect substantial rights without a showing of prejudice.
       In any event, the Second Circuit’s “any possibility,” however re
    mote, standard also cannot be reconciled with the criterion that “the
    error seriously affec[t] the fairness, integrity or public reputation of
    judicial proceedings.” Puckett, supra, at ___ (internal quotation
    marks omitted). Under the Second Circuit’s approach, a retrial
    would be required even where the evidence supporting conviction
    consists of a few days of preenactment conduct along with several
    continuous years of identical postenactment conduct. Given the tiny
    risk that a jury would base its conviction in these circumstances on
    the few preenactment days alone, such an error is most unlikely to
    cast serious doubt on the fairness, integrity, or public reputation of
    the judicial system. Pp. 3–8.
538 F. 3d 97, reversed and remanded.

  BREYER, J., delivered the opinion of the Court, in which ROBERTS,
C. J., and SCALIA, KENNEDY, THOMAS, GINSBURG, and ALITO, JJ., joined.
STEVENS, J., filed a dissenting opinion. SOTOMAYOR, J., took no part in
the consideration or decision of the case.
                        Cite as: 560 U. S. ____ (2010)                              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, Wash
     ington, 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. 08–1341
                                   _________________


 UNITED STATES, PETITIONER v. GLENN MARCUS
 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE SECOND CIRCUIT

                                 [May 24, 2010] 


   JUSTICE BREYER delivered the opinion of the Court.
   The question before us concerns an appellate court’s
“plain error” review of a claim not raised at trial. See Fed.
Rule Crim. Proc. 52(b). The Second Circuit has said that
it must recognize a “plain error” if there is “any possibil
ity,” however remote, that a jury convicted a defendant
exclusively on the basis of actions taken before enactment
of the statute that made those actions criminal. 538 F. 3d
97, 102 (2008) (per curiam) (emphasis added). In our view,
the Second Circuit’s standard is inconsistent with this
Court’s “plain error” cases. We therefore reverse.
                               I
  A federal grand jury indicted respondent Glenn Marcus
on charges that he engaged in unlawful forced labor and
sex trafficking between “ ‘January 1999 and October
2001.’ ” Id., at 100; see also 18 U. S. C. §§1589, 1591(a)(1).
At trial, the Government presented evidence of his conduct
during that entire period. 538 F. 3d, at 100. And a jury
found him guilty of both charges. Ibid.
  On appeal, Marcus pointed out for the first time that the
statutes he violated were enacted as part of the Traffick
ing Victims Protection Act of 2000 (TVPA), which did not
2                UNITED STATES v. MARCUS

                      Opinion of the Court

become law until October 28, 2000. §112(a)(2), 114 Stat.
1486. Marcus noted that the indictment and the evidence
presented at trial permitted a jury to convict him exclu
sively upon the basis of actions that he took before October
28, 2000. And for that reason, Marcus argued that his
conviction violated the Constitution—in Marcus’ view, the
Ex Post Facto Clause, Art. I, §9, cl. 3. Marcus conceded
that he had not objected on these grounds in the District
Court. Letter Brief for Appellant in No. 07–4005–cr
(CA2), p. 12. But, he said, the constitutional error is
“plain,” and his conviction therefore must be set aside.
Id., at 13.
   The Government replied by arguing that Marcus’ con
viction was for a single course of conduct, some of which
took place before, and some of which took place after, the
statute’s enactment date. 538 F. 3d, at 101. The Consti
tution, it said, does not forbid the application of a new
statute to such a course of conduct so long as the course of
conduct continued after the enactment of the statute. See,
e.g., United States v. Harris, 79 F. 3d 223, 229 (CA2 1996);
United States v. Duncan, 42 F. 3d 97, 104 (CA2 1994).
The Government conceded that the conviction could not
rest exclusively upon conduct which took place before the
TVPA’s enactment, but it argued that the possibility that
the jury here had convicted on that basis was “ ‘remote.’ ”
538 F. 3d, at 102. Hence, the Government claimed, it was
highly unlikely that the judge’s failure to make this aspect
of the law clear (say, by explaining to the jury that it could
not convict based on preenactment conduct alone) affected
Marcus’ “substantial rights.” Letter Brief for United
States in No. 07–4005–cr (CA2), p. 9. And the Govern
ment thus argued that the court should not recognize a
“plain error.” Ibid.
   The Second Circuit noted that Marcus had not raised
his ex post facto argument in the District Court. 538 F. 3d,
at 102. The court also recognized that, under Circuit
                  Cite as: 560 U. S. ____ (2010)             3

                      Opinion of the Court

precedent, the Constitution did not prohibit conviction for
a “ ‘continuing offense’ ” so long as the conviction rested, at
least in part, upon postenactment conduct. Id., at 101
(quoting Harris, supra, at 229). But, the court held, “even
in the case of a continuing offense, if it was possible for the
jury—wh[ich] had not been given instructions regarding
the date of enactment—to convict exclusively on [the basis
of] pre-enactment conduct, then the conviction constitutes
a violation” of the Ex Post Facto Clause. 538 F. 3d, at 101.
The court noted that this was “true even under plain error
review.” Ibid. In short, under the Second Circuit’s ap
proach, “a retrial is necessary whenever there is any
possibility, no matter how unlikely, that the jury could
have convicted based exclusively on pre-enactment con
duct.” Id., at 102 (emphasis added).
  The Government sought certiorari. And we granted the
writ, agreeing to decide whether the Second Circuit’s
approach to “plain error” review, as we have set it forth,
conflicts with this Court’s interpretation of the “plain
error” rule. See Fed. Rule Crim. Proc. 52(b).
                               II
  Rule 52(b) permits an appellate court to recognize a
“plain error that affects substantial rights,” even if the
claim of error was “not brought” to the district court’s
“attention.” Lower courts, of course, must apply the Rule
as this Court has interpreted it. And the cases that set
forth our interpretation hold that an appellate court may,
in its discretion, correct an error not raised at trial only
where the appellant demonstrates that (1) there is an
“error”; (2) the error is “clear or obvious, rather than sub
ject to reasonable dispute”; (3) the error “affected the
appellant’s substantial rights, which in the ordinary case
means” it “affected the outcome of the district court pro
ceedings”; and (4) “the error seriously affect[s] the fair
ness, integrity or public reputation of judicial proceed
4                UNITED STATES v. MARCUS

                      Opinion of the Court

ings.” Puckett v. United States, 556 U. S. ___, ___ (2009)
(slip op., at 6) (internal quotation marks omitted); see also
United States v. Olano, 507 U. S. 725, 731–737 (1993);
Johnson v. United States, 520 U. S. 461, 466–467 (1997);
United States v. Cotton, 535 U. S. 625, 631–632 (2002).
   In our view, the Second Circuit’s standard is inconsis
tent with the third and the fourth criteria set forth in
these cases. The third criterion specifies that a “plain
error” must “affec[t]” the appellant’s “substantial rights.”
In the ordinary case, to meet this standard an error must
be “prejudicial,” which means that there must be a rea
sonable probability that the error affected the outcome of
the trial. Olano, supra, at 734–735 (stating that, to satisfy
the third criterion of Rule 52(b), a defendant must “nor
mally” demonstrate that the alleged error was not “harm
less”); see also United States v. Dominguez Benitez, 542
U. S. 74, 83 (2004). The Court of Appeals, however, would
notice a “plain error” and set aside a conviction whenever
there exists “any possibility, no matter how unlikely, that
the jury could have convicted based exclusively on pre
enactment conduct.” 538 F. 3d, at 102 (emphasis added).
This standard is irreconcilable with our “plain error”
precedent. See, e.g., Olano, supra, at 734–735.
   We recognize that our cases speak of a need for a show
ing that the error affected the “outcome of the district
court proceedings” in the “ordinary case.” Puckett, 556
U. S., at ___ (slip op., at 6) (internal quotation marks
omitted). And we have noted the possibility that certain
errors, termed “structural errors,” might “affect substan
tial rights” regardless of their actual impact on an appel
lant’s trial. See id., at ___ (slip op., at 11) (reserving the
question whether “structural errors” automatically satisfy
the third “plain error” criterion); Cotton, supra, at 632
(same); Johnson, supra, at 469 (same); Olano, supra, at
735 (same). But “structural errors” are “a very limited
class” of errors that affect the “ ‘framework within which
                  Cite as: 560 U. S. ____ (2010)              5

                      Opinion of the Court

the trial proceeds,’ ” Johnson, supra, at 468 (quoting Ari
zona v. Fulminante, 499 U. S. 279, 310 (1991)), such that
it is often “difficul[t]” to “asses[s] the effect of the error,”
United States v. Gonzalez-Lopez, 548 U. S. 140, 149, n. 4
(2006). See Johnson, supra, at 468–469 (citing cases in
which this Court has found “structural error,” including
Gideon v. Wainwright, 372 U. S. 335 (1963) (total depriva
tion of counsel); Tumey v. Ohio, 273 U. S. 510 (1927) (lack
of an impartial trial judge); McKaskle v. Wiggins, 465
U. S. 168 (1984) (right to self-representation at trial);
Waller v. Georgia, 467 U. S. 39 (1984) (violation of the
right to a public trial); and Sullivan v. Louisiana, 508
U. S. 275 (1993) (erroneous reasonable-doubt instruction)).
We cannot conclude that the error here falls within that
category.
   The error at issue in this case created a risk that the
jury would convict respondent solely on the basis of con
duct that was not criminal when the defendant engaged in
that conduct. A judge might have minimized, if not elimi
nated, this risk by giving the jury a proper instruction.
We see no reason why, when a judge fails to give such an
instruction, a reviewing court would find it any more
difficult to assess the likely consequences of that failure
than with numerous other kinds of instructional errors
that we have previously held to be non-“structural”—for
example, instructing a jury as to an invalid alternative
theory of guilt, Hedgpeth v. Pulido, 555 U. S. ___ (2008)
(per curiam), omitting mention of an element of an offense,
Neder v. United States, 527 U. S. 1 (1999), or erroneously
instructing the jury on an element, Yates v. Evatt, 500
U. S. 391 (1991); Carella v. California, 491 U. S. 263
(1989) (per curiam); Pope v. Illinois, 481 U. S. 497 (1987);
Rose v. Clark, 478 U. S. 570 (1986).
   Marcus argues that, like the Second Circuit, we should
apply the label “Ex Post Facto Clause violation” to the
error in this case, and that we should then treat all errors
6                UNITED STATES v. MARCUS

                     Opinion of the Court

so labeled as special, “structural,” errors that warrant
reversal without a showing of prejudice. See Brief for
Respondent 27–29. But we cannot accept this argument.
As an initial matter, we note that the Government has
never claimed that the TVPA retroactively criminalizes
preenactment conduct, see Brief for United States 16, and
that Marcus and the Second Circuit were thus incorrect to
classify the error at issue here as an Ex Post Facto Clause
violation, see Marks v. United States, 430 U. S. 188, 191
(1977) (“The Ex Post Facto Clause is a limitation upon the
powers of the Legislature, and does not of its own force
apply to the Judicial Branch of government” (citation
omitted)). Rather, if the jury, which was not instructed
about the TVPA’s enactment date, erroneously convicted
Marcus based exclusively on noncriminal, preenactment
conduct, Marcus would have a valid due process claim. Cf.
Bouie v. City of Columbia, 378 U. S. 347, 353–354 (1964)
(applying Due Process Clause to ex post facto judicial
decisions). In any event, however Marcus’ claim is la
beled, we see no reason why this kind of error would
automatically “affect substantial rights” without a show
ing of individual prejudice.
  That is because errors similar to the one at issue in this
case—i.e., errors that create a risk that a defendant will be
convicted based exclusively on noncriminal conduct—come
in various shapes and sizes. The kind and degree of harm
that such errors create can consequently vary. Sometimes
a proper jury instruction might well avoid harm; other
times, preventing the harm might only require striking or
limiting the testimony of a particular witness. And some
times the error might infect an entire trial, such that a
jury instruction would mean little. There is thus no rea
son to believe that all or almost all such errors always
“affec[t] the framework within which the trial proceeds,”
Fulminante, supra, at 310, or “necessarily render a crimi
nal trial fundamentally unfair or an unreliable vehicle for
                 Cite as: 560 U. S. ____ (2010)          7

                     Opinion of the Court

determining guilt or innocence,” Neder, supra, at 9 (em
phasis deleted).
   Moreover, while the rights at issue in this case are
important, they do not differ significantly in importance
from the constitutional rights at issue in other cases
where we have insisted upon a showing of individual
prejudice. See Fulminante, supra, at 306–307 (collecting
cases). Indeed, we have said that “if the defendant had
counsel and was tried by an impartial adjudicator, there is
a strong presumption that any other errors that may have
occurred” are not “structural errors.” Rose, supra, at 579.
No one here denies that defendant had counsel and was
tried by an impartial adjudicator.
   In any event, the Second Circuit’s approach also cannot
be reconciled with this Court’s fourth “plain error” crite
rion, which permits an appeals court to recognize “plain
error” only if the error “seriously affect[s] the fairness,
integrity, or public reputation of judicial proceedings.”
Johnson, 520 U. S., at 467 (internal quotation marks
omitted). In cases applying this fourth criterion, we have
suggested that, in most circumstances, an error that does
not affect the jury’s verdict does not significantly impugn
the “fairness,” “integrity,” or “public reputation” of the
judicial process. Ibid. (internal quotation marks omitted);
Cotton, 535 U. S., at 633. The Second Circuit’s “any possi
bility, no matter how unlikely” standard, however, would
require finding a “plain error” in a case where the evi
dence supporting a conviction consisted of, say, a few days
of preenactment conduct along with several continuous
years of identical postenactment conduct. Given the tiny
risk that the jury would have based its conviction upon
those few preenactment days alone, a refusal to recognize
such an error as a “plain error” (and to set aside the ver
dict) is most unlikely to cast serious doubt on the “fair
ness,” “integrity,” or “public reputation” of the judicial
system.
8                UNITED STATES v. MARCUS

                      Opinion of the Court

   We do not intend to trivialize the claim that respondent
here raises. Nor do we imply that the kind of error at
issue here is unimportant. But the rule that permits
courts to recognize a “plain error” does not “remove” “se
riou[s]” errors “from the ambit of the Federal Rules of
Criminal Procedure.” Johnson, supra, at 466. Rather, the
“plain error” rule, as interpreted by this Court, sets forth
criteria that a claim of error not raised at trial must sat
isfy. The Second Circuit’s rule would require reversal
under the “plain error” standard for errors that do not
meet those criteria. We can find no good reason to treat
respondent’s claim of error differently from others. See
Puckett, 556 U. S., at ___ (slip op., at 14) (reviewing the
Government’s violation of a plea agreement for “plain
error”); Cotton, supra, at 631–632 (reviewing an indict
ment’s failure to charge a fact that increased defendant’s
statutory maximum sentence for “plain error”); Johnson,
supra, at 464 (reviewing the failure to submit an element
of the crime to the jury for “plain error”). Hence we must
reject the Second Circuit’s rule.
   For these reasons, the judgment of the Court of Appeals
is reversed. As the Court of Appeals has not yet consid
ered whether the error at issue in this case satisfies this
Court’s “plain error” standard—i.e., whether the error
affects “substantial rights” and “the fairness, integrity, or
public reputation of judicial proceedings”—we remand the
case to that court so that it may do so.
                                             It is so ordered.

  JUSTICE SOTOMAYOR took no part in the consideration
or decision of this case.
                 Cite as: 560 U. S. ____ (2010)            1

                    STEVENS, J., dissenting

SUPREME COURT OF THE UNITED STATES
                         _________________

                         No. 08–1341
                         _________________


 UNITED STATES, PETITIONER v. GLENN MARCUS
 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE SECOND CIRCUIT

                        [May 24, 2010] 


  JUSTICE STEVENS, dissenting.
  The Court’s opinion fairly summarizes our “plain error”
cases and shows how the Court of Appeals applied a novel
standard of review. Yet while it may have taken an un
usual route to get there, I find nothing wrong with the
Court of Appeals’ judgment. I am more concerned with
this Court’s approach to, and policing of, Federal Rule of
Criminal Procedure 52(b).
                              I
  On October 28, 2000, Congress enacted the Trafficking
Victims Protection Act (TVPA), 114 Stat. 1466. Respon
dent Glenn Marcus was convicted on two counts under the
TVPA: one for sex trafficking, in violation of 18 U. S. C.
§1591(a)(1), and one for forced labor, in violation of §1589.
The indictment charged conduct that spanned from Janu
ary 1999 to October 2001. See 538 F. 3d 97, 100 (CA2
2008) (per curiam). The evidence introduced by the Gov
ernment at trial spanned from 1998 to 2003. See 487
F. Supp. 2d 289, 292–297 (EDNY 2007). Most of the evi
dence supporting the sex trafficking charge, and some of
the evidence supporting the forced labor charge, related to
discrete events that occurred before October 28, 2000.
  At trial, Marcus failed to ask the judge to inform the
jury that his preenactment conduct was not unlawful, and
the judge failed to give an instruction to that effect. If a
2                UNITED STATES v. MARCUS

                    STEVENS, J., dissenting

request had been made, it is clear that an appropriate
instruction would have been given. Indeed, it is equally
clear that the judge would have given such an instruction
sua sponte if she had been aware of the effective date of
the statute. No one disputes that error was committed in
the way Marcus was charged and tried, and the error was
sufficiently plain to be considered on appeal.
  The record demonstrates that Marcus’ sex trafficking
conviction likely violated the ex post facto rule, as applied
to trial proceedings through the Due Process Clause, see
ante, at 6, because the postenactment evidence appears to
have been insufficient to prove guilt beyond a reasonable
doubt. See 538 F. 3d, at 105–106 (Sotomayor, J., concur
ring). Whether his forced labor conviction is invalid for
the same reason is not clear. What is clear, however, is
that neither the Second Circuit nor this Court has to
determine that an error of constitutional magnitude oc
curred for Marcus to be eligible for relief. The question
under Federal Rule of Criminal Procedure 52(b) is
whether the trial error was sufficiently weighty to affect
“substantial rights,” and in my view this error surely was.
  The Court notes that the error “created a risk that the
jury would convict respondent solely on the basis of con
duct that was not criminal when the defendant engaged in
that conduct.” Ante, at 5. That is true, and it is of funda
mental concern because imposing criminal sanctions for
nonproscribed conduct has always been considered a
hallmark of tyranny—no matter how morally reprehensi
ble the prosecuted party.
  But in addition to the very real possibility that the jury
convicted Marcus of sex trafficking solely on the basis of
preenactment conduct, the error created another risk:
namely, that both verdicts, returned after seven days of
deliberation, rested in part on the jury’s incorrect belief
that the conduct before October 28, 2000, was unlawful.
The error committed at trial not only prevented the jury
                      Cite as: 560 U. S. ____ (2010)                      3

                         STEVENS, J., dissenting

from focusing on the relevant time period, but it also
distorted the jury’s perception of Marcus’ actions. By
arguing that its preenactment evidence showed a violation
of the TVPA, the Government effectively mischaracterized
all of that evidence as descriptions of illegal behavior. And
by giving the jury the impression that Marcus committed
a much larger amount of criminal conduct than he really
did, the error may have tipped the scales in favor of the
prosecution, when the actual evidence of guilt would not
have persuaded the jury to convict.
   There is no need to decide whether the Government’s
arguments or the trial court’s failure to give a curative
instruction reached a level of unfairness sufficient to
violate the Due Process Clause. For the foregoing reasons,
I am convinced that the error prejudiced Marcus and
seriously undermined the integrity of the proceedings.
While I do not endorse the reasoning in the Court of Ap
peals’ opinion,* I would therefore affirm its judgment.



——————
   * The per curiam opinion contained a curious wrinkle, apart from
misclassifying the trial error. See ante, at 6. The per curiam applied a
standard from earlier Second Circuit cases that asked whether there
was any possibility the jury convicted the defendant exclusively on the
basis of preenactment conduct. 538 F. 3d 97, 101 (CA2 2008) (citing
United States v. Torres, 901 F. 2d 205, 229 (1990), United States v.
Monaco, 194 F. 3d 381, 386 (1999), and United States v. Harris, 79
F. 3d 223, 229 (1996)). As I read the Second Circuit precedents, how
ever, they used that standard to determine whether an ex post facto
violation occurred, not to determine whether that violation warranted
vacatur of the conviction pursuant to Federal Rule of Criminal Proce
dure 52(b). Torres is the only one of the cited cases that even consid
ered Rule 52(b), and its holding rested on a combination of factors,
including that “the defendants brought the general ex post facto ques
tion to the attention of the district court,” albeit imprecisely, and that a
mandatory life sentence was imposed. 901 F. 2d, at 229. It is thus
unclear why the Court of Appeals believed itself foreclosed from con
ducting a regular “plain error” review.
4                UNITED STATES v. MARCUS

                    STEVENS, J., dissenting

                              II
  The Court does not engage the merits of that judgment,
but instead remands to the Court of Appeals to apply the
test we have devised for evaluating claims of “plain error.”
That test requires lower courts to conduct four separate
inquiries, each of which requires a distinct form of judg
ment and several of which have generated significant
appellate-court dissensus; the test may also contain an
exception for “structural errors,” a category we have never
defined clearly. With great concision, the Court manages
to summarize all of these moving parts in about five
pages. Ante, at 3–8.
  Yet the language of Rule 52(b) is straightforward. It
states simply: “A plain error that affects substantial rights
may be considered even though it was not brought to the
court’s attention.” This is the mirror image of Rule 52(a),
which instructs courts to disregard any error “that does
not affect substantial rights.” The Federal Rules thus set
forth a unitary standard, which turns on whether the
error in question affected substantial rights (either in a
particular defendant’s case or in the mine run of compara
ble cases), and they leave it to judges to figure out how
best to apply that standard.
  In our attempt to clarify Rule 52(b), we have, I fear,
both muddied the waters and lost sight of the wisdom
embodied in the Rule’s spare text. Errors come in an
endless variety of “shapes and sizes.” Ante, at 6. Because
error-free trials are so rare, appellate courts must repeat
edly confront the question whether a trial judge’s mistake
was harmless or warrants reversal. They become familiar
with particular judges and with the vast panoply of trial
procedures, they acquire special expertise in dealing with
recurring issues, and their doctrine evolves over time to
help clarify and classify various types of mistakes. These
are just a few of the reasons why federal appellate courts
are “allowed a wide measure of discretion in the supervi
                 Cite as: 560 U. S. ____ (2010)           5

                    STEVENS, J., dissenting

sion of litigation in their respective circuits.” United
States v. Olano, 507 U. S. 725, 745 (1993) (STEVENS, J.,
dissenting). This Court’s ever more intensive efforts to
rationalize plain-error review may have been born of a
worthy instinct. But they have trapped the appellate
courts in an analytic maze that, I have increasingly come
to believe, is more liable to frustrate than to facilitate
sound decisionmaking.
  The trial error at issue in this case undermined the
defendant’s substantial rights by allowing the jury to
convict him on the basis of an incorrect belief that lawful
conduct was unlawful, and it does not take an elaborate
formula to see that. Because, in my view, the Court of
Appeals properly exercised its discretion to remedy the
error and to order a retrial, I respectfully dissent.
