OPINION
This case is an appeal by Juan Martinez and Juan Sauceda from their convictions and sentences stemming from their involvement in a drug conspiracy. Although Appellants raise a number of issues on appeal, the only claims that merit discussion are (1) Sauceda’s claim that the prosecution engaged in improper vouching/bolstering, and (2) Appellants’ claim that their sentences violate
Apprendi v. New Jersey,
I.
In February 1998, the Drug Enforcement Agency (“DEA”), based on their belief that Juan Sauceda was involved in marijuana sales, attempted to set up delivery of 400 pounds of marijuana to Sauceda. Juan Reyes, Ronald Carboni (an informant), and undercover DEA Agent Freeman met with Sauceda to discuss marijuana trafficking. They went to Saueeda’s hotel in Birch Run, Michigan, where he examined two different samples of mari *253 juana. Sauceda declined to purchase the marijuana, citing its poor quality. Sauce-da was later arrested at a hotel in Auburn Hills, Michigan. Subsequent to the arrest, the police located and searched three storage units rented by Sauceda. One unit contained approximately 282 pounds of marijuana.
In the meantime, Juan Reyes and Car-boni returned to the Houston, Texas area, where Juan Martinez arranged for 315 pounds of marijuana to be delivered to Reyes’ residence. Juan Martinez was later arrested at his home in Houston, Texas. During the search of Martinez’s home, officers found 47 pounds of marijuana.
Juan Martinez and Juan Sauceda were indicted in the Eastern District of Michigan along with four other co-defendants. Martinez and Sauceda were charged with conspiracy to distribute marijuana in violation of 21 U.S.C. § 846. Sauceda was also charged with possession with the intent to distribute in violation of 21 U.S.C. § 841(a)(1). A jury found Martinez and Sauceda guilty of conspiracy to distribute marijuana. The jury also found Sauceda guilty of possession with the intent to distribute. The district court found by a preponderance of the evidence that Martinez was responsible for. 1568.55 kg of marijuana and sentenced him to 210 months, based in part on that finding. 1 The district court found by a preponderance of the evidence that Sauceda was responsible for 1661 kg of marijuana. Based in part on that finding, the district court sentenced Sauceda to a term of 240 months on both the conspiracy and possession counts, to be served concurrently. 2
II.
Sauceda argues on appeal that the prosecutor improperly vouched for and bolstered the testimony of the Government’s main witness, informant Ronald Carboni. At trial, the district court overruled defense objections to the following questions posed by the Government to Rodney Glendening, a narcotics deputy:
Q: Now you’ve had the occasion to work with Mr. Carboni not only on this case but on some other eases?
A: Yes, Ma’am.
Q: Approximately how many?
A: Seven other cases.
Q: And what did you find about the information he had provided to you?
A: That the information he’s provided has always been credible, it’s been accurate and truthful.
J.A. at 358-359.
The Sixth Circuit in
United States v. Francis
stated that “[improper vouching occurs when a prosecutor supports the credibility of a witness by indicating a personal belief in the witness’s credibility
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thereby placing the prestige of the office of the United States Attorney behind that witness.”
Although the prosecutor’s attempt to elicit testimony in support of Carboni’s credibility is clearly not vouching, this line of inquiry does constitute improper bolstering. The Court in Francis stated that “[b]olstering occurs when the prosecutor implies that the witness’s testimony is corroborated by evidence known to the government but not known to the jury.” Id. at 551. Significantly, the Court provided that the prosecutor “may ask a government agent or other witnesses whether he was able to corroborate what he learned in the course of a criminal investigation. However, if the prosecutor pursues this line of questioning, she must also draw out testimony explaining how the information was corroborated and where it originated.” Id. (emphasis added). Thus, if a prosecutor asks a government agent whether the agent was able to corroborate information provided by an informant, the prosecutor must introduce to the jury how that information was corroborated, e.g., via documents or searches. Id.
In the case at bar, the prosecutor elicited testimony from narcotics deputy Glen-dening that in each of the seven prior cases where Carboni provided information to the police, the information had been corroborated. However, the prosecutor did not provide the jury with evidence of how, in those instances, the information was corroborated. It was precisely this type of omission that the Court in Francis deemed improper bolstering. Id. at 551 (“The prosecutor’s failure to introduce to the jury whether the information was corroborated via documents, searches, conversations, or other means would lead a reasonable jury to believe that the prosecutor was implying a guarantee of truthfulness based on facts outside the record.”). Here, we find that the prosecutor engaged in improper bolstering.
We now turn to the question of whether the improper bolstering amounts to prejudicial error. Upon a showing that comments were improper, a defendant must show that the impropriety was so flagrant that it required reversal because only a retrial could correct the error.
Id.
at 552. The standard for determining flagrancy is: (1) whether the statements tended to mislead the jury or prejudice the defendant; (2) whether the statements were isolated or among a series of improper statements; (3) whether the statements were deliberately or accidently before the jury; and (4) the total strength of the evidence against the accused.
Id
at 549-50;
United States v. Monus,
Sauceda raises a number of other issues, *255 all of which are without merit. 3
III.
Appellants argue that their sentences should be vacated pursuant to the Supreme Court’s recent decision in
Apprendi v. New Jersey,
The Supreme Court established in
Apprendi
that “[ojther than the fact of a prior conviction, any fact that increases the penalty for a crime beyond the prescribed statutory maximum must be submitted to a jury, and proved beyond a reasonable doubt.”
Appellants must also demonstrate that the error affected their substantial rights and undermined the fairness of the proceedings.
See Johnson,
IV.
Because the Apprendi error affected Appellants’ substantial rights and undermined the fairness of the proceedings, we VACATE their respective sentences and REMAND for resentencing.
Notes
. Based on the quantity of drugs attributed to Martinez, the court found that Martinez’s base offense level was 32 pursuant to U.S. Sentencing Guideline Manual § 2D 1.1 (a)(3)(c)(4) (1998). The court enhanced his offense level by two levels pursuant to § 2D 1.1 (b)(1) for possession of a dangerous weapon, for a total offense level of 34. The court found that Martinez was in criminal history category II, which, combined with the total offense level, produced a sentencing range of 168-210 months.
. Based on the quantity of drugs attributed to Sauceda, the court found that Sauceda’s base offense level was 32 pursuant to U.S.S.G. § 2D1.1 (a)(3)(c)(4). The district court enhanced his offense level by two levels for obstruction of justice pursuant to § 3C1.1. The court also enhanced his offense level another three levels for his role in the offense pursuant to § 3B1.1 for a total offense level of 37. The court found that Sauceda had a criminal history category of I, which, combined with the total offense level, produced a sentencing range of 210-262 months.
. The district court did not abuse its discretion in admitting, under Fed.R.Evid. 801(d)(2)(E), statements of the co-conspirators which were made in furtherance of the conspiracy. Also, the district court's findings of fact with regard to the obstruction of justice enhancement (U.S.S.G. § 3C1.1) and the role in the offense enhancement (U.S.S.G. § 3B1.1) were not clearly erroneous.
. 21 U.S.C. § 841(b)(1)(D) also provides for a statutory maximum of ten years if the defendant has a prior felony drug conviction. The Government argues that the ten year statutory maximum applies to Sauceda’s sentence in light of his prior felony drug conviction. The Government overlooks 21 U.S.C. § 851 which provides that "[n]o person who stands convicted of an offense under this part shall be sentenced to increased punishment by reason of one or more prior convictions, unless before trial, or before entry of a plea of guilty, the United States attorney files an information with the court....” The Government did not file such an information before trial, thus, it can not now rely on Sauceda's prior conviction to increase his sentence under § 841(b)(1)(D).
.Sauceda was sentenced to a term of 240 months (20 years) on both the conspiracy and possession counts to be served concurrently. The prescribed statutory maximum for each count is five years under 21 U.S.C. § 841(b)(1)(D). On remand, even if the district court opts to run the sentences for both counts consecutively, the total punishment that will result is 10 years, which is less than Sauceda’s current 20 year sentence. Clearly, Sauceda's substantial rights were affected by
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the
Apprendi
error.
Cf. United States v. Taylor,
No. 99-1557,
. Wc decline Appellants’ invitation to find that 21 U.S.C. § 841 is unconstitutional in light of the Supreme Court’s decision in
Ap-prendi.
Appellants argue that the drug statute is unconstitutional because Congress intended for drug quantity to be a sentencing factor; whereas,
Apprendi
requires drug quantity to be submitted to the jury for proof beyond a reasonable doubt. The Appellants’ argument rests on an untenably broad and erroneous reading of
Apprendi.
The Supreme Court in
Apprendi
expressly declined to overrule its earlier holding that sentencing factors may be used to increase the penalty for an offense under a preponderance of the evidence standard.
See
