Andújar argues that his case is distinguishable from the above cases because the challenged testimony here refers directly to his express assertion of his constitutional rights. In the above cases, Andújar argues, the challenged testimony mentioned only the defendant's refusal to answer further questions. See Burns, 276 F.3d at 441 (federal agent testified that the defendant, in response to one particular question, "did not respond and `just looked' at those questioning him"); Harris, 956 F.2d at 181 (prosecutor's summation mentioned the defendant's confession and that the defendant thereafter "conclude[d] the interview"); Rowan, 752 F.2d at 1190 (two police officers testified that after the defendant answered some questions he "said he didn't want to say anything else"); Collins, 652 F.2d at 740 (officers testified that after making an incriminating statement, the defendant "refused to make any other statement"). In contrast, Andújar argues, Bryan's testimony explicitly noted that Andújar had asked for a lawyer and had "invoked his Miranda warnings."

Andújar raises a meaningful distinction. It has long been established that a witness who has been compelled to testify may avoid a question on Fifth Amendment grounds only if the answer would pose "some authentic danger of incrimination." United States v. Castro, 129 F.3d 226, 229 (1st Cir.1997). In light of the self-evident purpose of the privilege against self-incrimination, a government witness's testimony that an accused explicitly invoked the privilege raises a nearly irresistible inference that the accused was hiding something incriminating. Put another way, although silence may be interpreted in many ways, see Doyle, 426 U.S. at 617, 96 S. Ct. 2240 ("every post-arrest silence is insolubly ambiguous"), the affirmative assertion of the privilege against self-incrimination raises a clear inference of culpability. Accordingly, since such testimony more directly implies that the defendant was hiding something, it is necessarily more prejudicial than testimony that simply notes that the defendant at some point stopped answering questions. Indeed, the distinction between an affirmative statement and simple silence was one important factor in Coppola. See 878 F.2d at 1566 (distinguishing from Supreme Court precedent upholding the use of pre-arrest silence to impeach a defendant's credibility because, "[i]n the case at bar, we are concerned with the use of a statement made by a suspect and used by the prosecutor in his case in chief, not the use of silence to impeach the defendant's credibility").

More importantly, although Miranda acknowledges the possibility of a knowing and voluntary waiver, neither Miranda, nor any subsequent Supreme Court decision, draws a distinction between an immediate post-arrest Fifth Amendment assertion and a delayed mid-interrogation assertion. In either event, the assertion triggers the privilege, the police must cease interrogation, and the government may not use the assertion against the defendant at trial. See Doyle, 426 U.S. at 619, 96 S. Ct. 2240; Miranda, 384 U.S. at 468 n. 37, 86 S. Ct. 1602 ("In accord with our decision today, it is impermissible to penalize an individual for exercising his Fifth Amendment privilege when he is under police custodial interrogation. The prosecution may not, therefore, use at trial the fact that he stood mute or claimed his privilege in the face of accusation."). At least with respect to clear affirmative assertions, we do not see how an initial Miranda waiver can operate to make a subsequent Miranda assertion admissible against the defendant, nor do we perceive a sound rationale for cutting back the scope of Miranda's protections. See Coppola, 878 F.2d at 1566 (noting that the privilege against self-incrimination is given liberal application and cautioning against "whittl[ing] it down by the subtle encroachments of judicial opinion") (quoting Maffie v. United States, 209 F.2d 225, 227 (1st Cir.1954)); see also Castro, 129 F.3d at 229 (recognizing that the privilege against self-incrimination is "a cornerstone of our adversarial system of criminal justice" that "must not be given a crabbed construction").

Whatever the merit of the reasoning of the Eighth Circuit cases, there are limits to how far the government may go in describing the scope of an interrogation. See Rowan, 752 F.2d at 1190 (recognizing that the police can "indicate . . . the end as well as the beginning of the interrogation, so that the jury [will] know that the officers' testimony [is] complete," "provided [that] they [do] not do so with undue emphasis"). Government witnesses who testify concerning the circumstances of an interrogation that was terminated by the defendant must proceed with caution. In the circumstances of this case, we hold that the Fifth Amendment bars testimony concerning a defendant's explicit mid-interrogation assertion of his Miranda rights, and that it was error to permit such testimony to go to the jury.

The government argues, nevertheless, that in light of the Eighth Circuit cases, and a case from this circuit that favorably cites one of those cases, see United States v. Lopez-Lopez, 282 F.3d 1, 12 (1st Cir. 2002) (citing Harris, 956 F.2d at 181), the district court's error was not plain. As noted above, because the Fifth Amendment privilege against self-incrimination "must be given liberal construction," Coppola, 878 F.2d at 1565, any exceptions that undermine its protections should be applied narrowly.

It is important to emphasize that the Eighth Circuit cases did not confront the precise scenario presented here. See supra at 556. Neither did Lopez-Lopez. In that case, two co-defendants were questioned together and in response to a specific question, one co-defendant told the other "don't answer." Lopez-Lopez, 282 F.3d at 11. The district court allowed the interrogating officer to testify regarding that statement at the defendants' joint trial. We upheld their convictions, holding that, after an accused knowingly and voluntarily waives his Miranda rights by making statements, "he may not rely on Doyle to object to the admission of those statements simply because the statements refer to the act of keeping silent." Id. at 12. As in the Eighth Circuit cases, the testimony challenged in Lopez-Lopez did not describe the defendant expressly electing to exercise his Miranda rights. Moreover, Lopez-Lopez is further distinguishable by the fact that it did not involve an accused asserting his own Miranda rights, but rather involved an accused urging his companion to assert his rights.

In sum, Miranda draws no distinction between a mid-interrogation assertion of the privilege against self-incrimination and an immediate post-arrest assertion, see Miranda, 384 U.S. at 468 n. 37 & 475-76, 86 S. Ct. 1602, and our holding in Coppola makes it clear that the words the defendant uses to assert the privilege are themselves protected by it, see Coppola, 878 F.2d at 1567-68. We reject the contention that any subsequent cases, of this circuit or of any other circuit, can be read to have carved out an exception to this protection where the express assertion of the privilege comes after a previous waiver. Such an exception would run contrary to Miranda's plain language. Accordingly, we find that it was plain error to allow testimony concerning Andújar's express assertion of his Miranda rights.

Such a finding, however does not end the plain error analysis. Andújar must establish that the error affected his "substantial rights by altering the outcome of the trial." United States v. Shoup, 476 F.3d 38, 42 (1st Cir.2007). Put another way, he must establish that the error prejudiced him. Given the overwhelming strength of the government's case, we conclude that it did not.

Although the government's case largely hinged on the testimony of a confidential informant, his testimony was corroborated by several sources, including the testimony of Officer Vidal and Agent Bryan, and the recorded conversations between the informant and Cancel. Bryan's and Vidal's testimony, and the substance of the recorded conversations, track the informant's testimony. Moreover, Vidal personally identified Andújar as being on the other end of the calls Cancel made to set up the time and the place for the seller to receive payment for the five kilograms of cocaine. The phone records for Cancel's and Andújar's mobile phones — which show a number of calls between Cancel and Andújar during the time period of the conspiracy — further support the informant's story.

The defendant's own actions and statements provide further corroboration. Andújar's very arrival at the appointed time and place designated for the transfer of the $85,000 is strong circumstantial evidence of his involvement in the conspiracy, especially when viewed in context with the other evidence. Moreover, Andújar's post-arrest confession that he was the owner of the seventy grams of cocaine found in the white BMW provides additional circumstantial evidence linking Andújar to the conspiracy. Both the quantity and the packaging of the seventy grams of cocaine, in 110 individual plastic bags, were consistent with distribution. See United States v. Puckett, 405 F.3d 589, 601 (7th Cir.2005) (noting that "63 grams [of cocaine], is in excess of what one would possess for personal use, and is in and of itself sufficient evidence to compel an inference that [the defendant] intended to distribute the drug"). Andújar's possession of the seventy grams — although not directly probative of his ownership of the five kilograms — lends credibility to the informant's depiction of Andújar as a drug dealer and undermines the defense testimony aimed at establishing an innocent explanation for Andújar's presence at the shopping center parking lot.

Andújar argues that the credibility of the government's identification is in doubt because the officers who arrested Andújar inquired whether other people at the scene were "Richard." But the fact that the arresting officers may not have known what Andújar looked like hardly undermines the government's case. Admittedly, the DEA relied on Cancel to make a visual identification of the seller, and he did just that. Andújar also argues that "the short duration of calls between Cancel and [Andújar], the lack of certainty as to what was spoken between them during those calls, [and] that there was evidence Cancel had direct communication with the owners of the narcotics whom he did not identify to the authorities at the time of arrest" further undermines the government's case. Again, however, it is not readily apparent how any of these factors weaken the government's case. It is hardly surprising that a drug dealer would want to minimize the length of his phone conversations concerning an illicit transaction. Nor is the government charged with providing the precise contents of every conversation involved in a conspiracy. In any event, the detailed testimony of the confidential informant, and the testimony of Officer Vidal, who listened in on three of Cancel's calls with Andújar, could hardly be characterized as "uncertain." Finally, that Cancel may have had contact with Andújar's source does not disprove Andújar's participation, especially in light of the testimony that the source trusted only Andújar and would not work directly with anyone else.

We therefore find that Andújar has failed to establish that the error "had [a] prejudicial impact on the jury's deliberations." Olano, 507 U.S. at 734, 113 S. Ct. 1770 (internal quotation marks omitted). For the same reason, Andújar's unpreserved challenge to the day three "on board" testimony also fails.

Andújar did, however, object to the day four testimony. Although not perceiving a problem, the district court sustained Andújar's objection, struck the offending testimony from the record, and instructed the jury as requested by Andújar. Thus, the only question presented on appeal is whether the granting of greater relief (i.e., the declaration of a mistrial) was warranted. Although we ordinarily review de novo the question of whether "a statement in the presence of the jury infringed upon the privilege against self-incrimination," we review the "denial of a motion for mistrial for abuse of discretion." Gabriele, 63 F.3d at 70.

The connection between Bryan's testimony about the DEA's post-arrest "attempt[] to have Mr. Andújar . . . get on board" and Andújar's election to remain silent is tenuous at best. The question posed by the government — asking Bryan how and for what purpose he had used Andújar's cell phone — did not call for such testimony. On its face, the testimony itself does not explicitly suggest that Andújar refused to talk to police, nor does it state whether the DEA's "attempt" was ultimately successful. See Lopez-Lopez, 282 F.3d at 12 (finding no Doyle violation where there "was no testimony as to whether [the co-defendant] responded to [the defendant's] suggestion by remaining silent and there was no testimony about either party remaining silent in the face of questioning"). Nor did the government make "a point of asking the jury to draw a negative inference from" the attempt to get Andújar "on board." United States v. Daoud, 741 F.2d 478, 482 (1st Cir.1984).

Even assuming the jury made the connection Andújar fears, viewing the totality of the circumstances, we do not perceive a violation of constitutional magnitude. In a recent habeas case, we recognized that in cases involving testimony concerning a defendant's post-Miranda silence, where the trial court promptly addresses the improper testimony "in an instruction to disregard and/or strike from the record, there may not necessarily be a Doyle violation because the government has not been permitted to `use' the defendant's silence against him." Ellen v. Brady, 475 F.3d 5, 11 (1st Cir.2007) (citing Greer v. Miller, 483 U.S. 756, 764-65, 107 S. Ct. 3102, 97 L. Ed. 2d 618 (1987)). In Ellen, a government witness, responding to a seemingly innocuous question from the prosecutor, testified concerning the defendant's election not to speak to the police. Id. at 7. The defendant immediately objected and the trial court sustained the objection, struck the testimony, and delivered a curative instruction. Id. at 8. In light of the surrounding circumstances, we ruled that there was no constitutional violation. See id. at 12-14. Important to our consideration were the facts that the defendant's "post-Miranda silence was not mentioned, by either the prosecutor or a witness, after the judge sustained the objection[,]" the government's questions "did not, on their face, call for testimony in violation of Doyle," and the court promptly delivered curative instructions that "were proportional to the" offensive testimony. Id. at 14.

The same factors are present here. The district court sustained Andújar's objection and struck the offending testimony from the record. Following Andújar's objection, no further questions or testimony alluded to his silence and the government made no comment on his silence in closing arguments. Additionally, the jury was instructed, both at the beginning of the trial and after the close of evidence, that it must not consider any testimony stricken from the record. Following closing arguments, the court, at Andújar's request, again emphasized this point, reminding the jury "that any testimony that you may have seen or heard and that I have excluded from evidence, and instructed you to disregard, is not evidence." The court also instructed the jury that Andújar has a "constitutional right not to testify and no inference of guilt or of anything else, may be drawn from the fact that he did not testify. For any of you to draw such an inference would be wrong, indeed it would be a violation of your oath as a juror." Andújar presents no sound reason to discard "the customary presumption that juries follow their instructions." Gabriele, 63 F.3d at 70; see also Ellen, 475 F.3d at 13.

Andújar argues that we should view the challenged day four testimony in context with the previous improper testimony. Andújar argues that the government purposefully elicited Bryan's improper testimony and the district court should have considered the cumulative effect of all the improper testimony. First, as noted above, we disagree that the government purposefully sought to elicit testimony about Andújar exercising his Fifth Amendment privilege. Additionally, it bears emphasizing that this court reviews alleged errors of the district court, not errors of the prosecution, and the district court is not charged with advocating for the defense or anticipating issues not brought to the fore by counsel. Cf. United States v. McIntosh, 380 F.3d 548, 555 (1st Cir.2004). Andújar never referred the court to the most objectionable testimony directly relating to his Miranda assertion. He only objected to the ambiguous and considerably less striking "on board" testimony. In such circumstances, the court did not abuse its discretion in denying Andújar's motion for a mistrial.3

Andújar challenges three comments made by the government in closing arguments. First, at the end of his initial summation, the prosecutor stated, "I feel comfortable and the United States feels comfortable that they have proven beyond a reasonable doubt that this man delivered five kilograms of cocaine between the 20 and 23 of September." Day Five Tr. at 39. In rebuttal, the prosecutor argued, inter alia, that Andújar and Cancel "conspired to distribute five kilograms of cocaine, it does not matter where it came from. He gave it to Freddy Cancel. That is what matters. I have proven it, absolutely. We have met our burden." Id. at 59. Finally, in his last words to the jury, the prosecutor urged, "[y]ou find him guilty, you uphold the law, your duty as jurors, make the logical choice and come back with one answer, and telling this man, Richard Andújar you are guilty. Thank you." Id. at 67.

Andújar argues that the first two remarks were improper because they amounted to "affirmations of [the prosecutor's] personal belief" that Andújar is guilty. See United States v. Gonzalez Vargas, 558 F.2d 631, 632-33 (1st Cir. 1977) (vacating a conviction where the prosecutor stated his personal belief in summation). Further inflaming the jurors' passions, Andújar argues, was the prosecutor's final exhortation to the jurors to do "your duty." See United States v. Mandelbaum, 803 F.2d 42, 44 (1st Cir. 1986) (finding improper the suggestion that a jury has "a duty to decide one way or the other" because such an appeal "can only distract a jury from its actual duty: impartiality"). Andújar contends that the severity of these comments warrants a new trial. The government concedes that the comments were improper, but argues that a new trial is unnecessary because it is not reasonably likely these isolated remarks affected the outcome of the trial.4

Since Andújar did not object to the prosecutor's remarks at trial, we may only review for plain error. See United States v. Henderson, 320 F.3d 92, 105 (1st Cir. 2003). The government explicitly concedes error and implicitly concedes that the error was plain. Nevertheless, as we have already noted above, see supra 558-59, 560 n. 3, the record, viewed in the aggregate, presents overwhelming evidence establishing Andújar's guilt. In such circumstances, we are compelled to conclude that the prosecutor's improper remarks did not "so poison[ ] the well that the trial's outcome was likely affected." Henderson, 320 F.3d at 107 (internal quotation marks omitted).5

For the foregoing reasons, the defendant's convictions are affirmed.