186 F.3d 1177 (9th Cir. 1999)
UNITED STATES OF AMERICA, Plaintiff-Appellee,v.DU BO, Defendant-Appellant.
No. 97-10443
UNITED STATES COURT OF APPEALS  FOR THE NINTH CIRCUIT
Argued and Submitted  November 2, 1998Memorandum Disposition Decided January 7, 1999Memorandum Disposition Withdrawn August 10, 1999Decided August 10, 1999

G. Anthony Long, Saipan, MP, for the defendant-appellant.
David Wood, Assistant United States Attorney, Saipan, MP,  for the plaintiff-appellee.
Appeal from the United States District Court  for the Northern Mariana Islands  Alex R. Munson, Chief Judge, Presiding. D.C. No. CR-97-00009-ARM.
Before: Alfred T. Goodwin, Robert R. Beezer and  Thomas G. Nelson, Circuit Judges.
OPINION
BEEZER, Circuit Judge:


1
Du Bo appeals his conviction for interference with commerce by extortion, in violation of 18 U.S.C. S 1851. We have  jurisdiction, 28 U.S.C. S 1291, and we reverse. We hold that,  if properly challenged prior to trial, an indictment's complete  failure to recite an essential element of the charged offense is not a minor or technical flaw subject to harmless error analysis, but a fatal flaw requiring dismissal of the indictment.


2
Du Bo was charged by indictment with a violation of 18  U.S.C. S 1851 ("the Hobbs Act"). More than two months  before trial, he unsuccessfully challenged the indictment as  defective for failing to specify the necessary mens rea. On  appeal, he argues that the indictment is fatally flawed and that  he need not show prejudice from the flaw to obtain reversal.  We agree.


3
Although not stated in the Hobbs Act itself, criminal  intent -- acting "knowingly or willingly" -- is an implied and  necessary element that the government must prove for a  Hobbs Act conviction. United States v. Soriano , 880 F.2d  192, 198 (9th Cir. 1989). "[I]mplied, necessary elements, not  present in the statutory language, must be included in an  indictment." United States v. Jackson, 72 F.3d 1370, 1380  (9th Cir. 1995). The indictment charges Du Bo only with  "unlawfully" affecting commerce by the "wrongful" use of  force. Under our Hobbs Act jurisprudence, such terms do not  connote the proper mens rea for a Hobbs Act conviction. See  United States v. Aguon, 851 F.2d 1158, 1168 (9th Cir. 1988),  overruled on other grounds by Evans v. United States , 504  U.S. 255 (1992). The indictment on its face is deficient. The  issue we decide today is whether the deficiency is amenable  to harmless error review. We conclude that it is not.


4
Du Bo's conviction requires reversal because his indictment fails to ensure that he was prosecuted only "on the basis  of the facts presented to the grand jury . . . . " United States v. Rosi, 27 F.3d 409, 414 (9th Cir. 1994). At common law,  "the most valuable function of the grand jury was. . . to stand  between the prosecutor and the accused, and to determine  whether the charge was founded upon credible testimony  . . . ." Hale v. Henkel, 201 U.S. 43, 59 (1906). Incorporated  into the Fifth Amendment by the Founders, there is "every  reason to believe that our constitutional grand jury was  intended to operate substantially like its English progenitor."  Costello v. United States, 350 U.S. 359, 362 (1956). The Fifth  Amendment thus requires that a defendant be convicted only  on charges considered and found by a grand jury. See United  States v. Hooker, 841 F.2d 1225, 1230 (4th Cir. 1988).


5
Failing to enforce this requirement would allow a court  to "guess as to what was in the minds of the grand jury at the  time they returned the indictment . . . ." United States v. Keith,  605 F.2d 462, 464 (9th Cir. 1979) (citing Russell v. United  States, 369 U.S. 749, 770 (1962)). Such guessing would  "deprive the defendant of a basic protection that the grand  jury was designed to secure," by allowing a defendant to be  convicted "on the basis of facts not found by, and perhaps not  even presented to, the grand jury that indicted him. " Id. (citing Russell, 369 U.S. at 770). We may only guess whether the  grand jury received evidence of, and actually passed on, Du  Bo's intent. We may never know if the grand jury would have  been willing to ascribe criminal intent to Du Bo. See Stirone  v. United States, 361 U.S. 212,217 (1960) (no court may  "know" what the grand jury "would have been willing to  charge"). Refusing to reverse in such a situation would impermissibly allow conviction on a charge never considered by the  grand jury. See id. at 219; see also United States v. Miller, 471 U.S. 130, 139-140 (1985).1


6
Du Bo's conviction also must be overturned because his  indictment lacks a necessary allegation of criminal intent, and  as such does not "properly allege an offense against the  United States." United States v. Morrison, 536 F.2d 286, 289  (9th Cir. 1976); see also United States v. Carll , 105 U.S. 611,  613 (1881) (such indictment fails to charge defendant with  any crime). Such a failure "generally constitutes a fatal  defect" that can not be cured through jury instructions, Keith,  605 F.2d at 464, because a "completely missing essential  element" leaves "nothing for a petit jury to ratify," Hooker,  841 F.2d at 1232.2 Specifically, the "failure to include the ele ment of willfulness . . . renders [an] indictment constitutionally defective." United States v. Kurka, 818 F.2d 1427, 1431  (9th Cir. 1987). It is not amenable to harmless error review.  See United States v. Spruill, 118 F.3d 221, 227 (4th Cir. 1997).3


7
The government is correct that challenges to minor or  technical deficiencies, even where the errors are related to an  element of the offense charged and even where the challenges  are timely, are amenable to harmless error review. See United  States v. Neill, 166 F.3d 943, 947-48 (9th Cir. 1999), cert.  denied, 119 S. Ct. 2037 (1999). The complete failure to  charge an essential element of a crime, however,"is by no  means a mere technicality." See United States v. King, 587  F.2d 956, 963 (9th Cir. 1978). As the Supreme Court stated  over a century ago, the omission of a necessary element of an  offense is a "matter of substance, and not a defect or imperfection in matter of form only . . . ." Carll , 105 U.S. at 613  (internal quotation marks omitted). Considering the indict- ment in its entirety and construing it according to common  sense as we must, see United States v. Alber, 56 F.3d 1106,  1111 (9th Cir. 1995), Du Bo's indictment was terminally  defective. The error was no mere clerical error; the indictment  listed specific legal terms that do not, for purposes of the  Hobbs Act, state the requisite intent. See Aguon , 851 F.2d at  1168.


8
Because the indictment charging Du Bo failed to include a  necessary element of the offense at issue, and because Du Bo  timely raised a challenge, the indictment was fatally flawed.  Accordingly, we reverse the judgment against Du Bo and  direct the district court to dismiss the indictment.


9
REVERSED AND REMANDED.



Notes:


1
 The standard for reviewing flaws in the indictment should not be confused with the standard for reviewing flaws in the grand jury proceeding  which led to the indictment. "Errors in the grand jury indictment procedure are subject to harmless error analysis unless the structural protections  of the grand jury have been compromised as to render the proceedings  fundamentally unfair." United States v. Oliver, 60 F.3d 547, 549 (9th Cir.  1994) (internal quotation marks and alterations omitted); see also People  of Territory of Guam v. Muna, 999 F.2d 397, 399 (9th Cir. 1993) (standard  for dismissal differs when considered prior to or after trial).


2
 The Supreme Court recently held that the failure to submit an element  of an offense to a petit jury is subject to harmless error analysis. See Neder  v. United States, 119 S. Ct. 1827 (1999). We do not apply Neder here. First, on its face, Neder applies to petit, not grand, juries. Second, an error  in a petit jury instruction is "simply an error in the trial process itself," id.  at 1833 (quotation marks omitted), which can be assessed in the context  of the trial. Conversely, errors in a grand jury indictment allow only a  "guess as to what was in the minds of the grand jury at the time . . . ." See  Russell v. United States, 369 U.S. 749, 770 (1962)). Third, the Court  focused on whether an error in a petit jury instruction would "necessarily  render a trial fundamentally unfair." Neder , 119 S. Ct. at 1833. In the  insufficient indictment context, the fact that a defendant received a fair  trial and suffered no prejudice is "irrelevant. " United States v. Daniels,  973 F.2d 272, 275-76 (4th Cir. 1992). Until the Court applies Neder's  holding to the grand jury context or otherwise alters its grand jury jurisprudence, the rule that a timely challenged indictment that fails to contain  elements of a crime requires reversal per se shall remain "a vital part of  our Federal criminal jurisprudence." See United States v. Spinner, 180 F.3d 514 (3d Cir. June 16, 1999) (decided after Neder) (internal  quotation marks omitted).


3
 Our holding is limited to cases where a defendant's challenge is timely.  Applying harmless error to a timely challenge would make "a pretrial  motion charging the insufficiency of the indictment . . . self-defeating . . .  because the motion could not have been brought without actual notice of  the missing element." Hooker, 841 F.2d at 1230. Untimely challenges to  the sufficiency of an indictment are reviewed under a more liberal standard. See, e.g., United States v. James , 980 F.2d 1314, 1318 (9th Cir.  1992); United States v. Coleman, 656 F.2d 509, 510 (9th Cir. 1981); Souza  v. United States, 304 F.2d 274, 276-77 (9th Cir. 1962).


