          United States Court of Appeals
                       For the First Circuit


No. 16-1104

                     UNITED STATES OF AMERICA,

                             Appellee,

                                 v.

                           BARRY SPENCER,

                       Defendant, Appellant.


          APPEAL FROM THE UNITED STATES DISTRICT COURT
                FOR THE DISTRICT OF MASSACHUSETTS

              [Hon. Rya W. Zobel, U.S. District Judge]


                               Before

                  Torruella, Kayatta, and Barron,
                          Circuit Judges.


     Karen A. Pickett, with whom Pickett Law Offices, P.C. was on
brief, for appellant.
     Cynthia A. Young, Assistant United States Attorney, with whom
William D. Weinreb, Acting United States Attorney, was on brief,
for appellee.


                          August 23, 2017
           BARRON, Circuit Judge.         Barry Spencer was convicted in

federal court of one count of possession with intent to distribute

cocaine base, in violation of 21 U.S.C. § 841(a) and 18 U.S.C.

§ 2, and one count of conspiracy to possess with intent to

distribute cocaine base, in violation of 21 U.S.C. § 846.          He now

appeals the District Court's denial of his motion for a new trial,

which relied primarily on the government's alleged violation of

Brady v. Maryland, 373 U.S. 83 (1963).        Spencer also challenges on

appeal the admission at trial of certain testimony from two police

officers concerning Spencer's conduct during (and immediately

preceding) the undercover drug purchase that led to the charges

against Spencer, certain statements made by the prosecutor during

closing argument, and the decision by the Magistrate Judge assigned

to   Spencer's   case   to   deny   discovery   on   Spencer's   claim   of

vindictive prosecution.      Finding no merit to these challenges, we

affirm.

                                     I.

           We first recount key aspects of the record developed at

Spencer's trial (which followed an earlier mistrial) and at two

post-trial hearings before the District Court.          We recount, too,

the procedural history of the case. Because a number of the issues

that Spencer raises on appeal are quite fact-dependent, we focus

up front on only those facts that pertain to his conviction on the

two drug counts.    We thus reserve a full discussion of the facts


                                    - 2 -
relevant to the specific challenges that Spencer raises on appeal

for our consideration of the merits of the challenges.           We do,

however,   provide    sufficient   detail   regarding   the   procedural

history to isolate the particular issue on which his primary

challenge -- concerning the alleged Brady violation -- hinges.

                                    A.

           According to testimony at trial, on March 20, 2013, two

members of the Boston Police Department (“BPD”) -- Detective

Sergeant Donald Keenan and Officer Richard Casallas -- identified

Spencer as someone who was potentially selling drugs in the

Egleston Square area of Roxbury, one of Boston's neighborhoods.

According to Keenan's trial testimony, Keenan was familiar with

Spencer "from the neighborhood" and made the decision to deploy

Casallas, who was working undercover, to make a drug purchase.

Casallas then approached Spencer and asked if Spencer was “on.”

Spencer responded that he was “always on,” and Casallas then asked

Spencer if he could purchase $20 of crack cocaine.        Spencer told

Casallas to follow him, and the two men briefly walked down the

street together.     Spencer then told Casallas to return to the bus

stop where they had started.

            Several minutes later, according to testimony at trial,

Spencer came back with Michael Morrison.      Casallas testified that,

with Spencer "scanning the area, looking at car[s] as they drove

by," Morrison sold Casallas a small bag of crack cocaine in


                                   - 3 -
exchange for $20.       Casallas and Spencer and Morrison then went

their separate ways.

            Spencer was arrested several days later, on May 26, 2013,

in connection with the undercover purchase of the crack cocaine.1

Thereafter, the case was transferred to federal authorities for

prosecution, and, on June 26, 2013, Spencer was indicted by a

federal grand jury and charged with one count of possession with

intent to distribute cocaine, in violation of 21 U.S.C. § 841(a)

and 18 U.S.C. § 2.      In a superseding indictment filed on August

28, 2013, the government also charged Spencer with one count of

conspiring -- with Morrison -- to possess with intent to distribute

cocaine, in violation of 21 U.S.C. § 846.            On March 26, 2014, the

government filed a second superseding indictment that specified

that the controlled substance was cocaine base, not cocaine.

            Spencer's   first   trial   on   these    charges   ended   in   a

mistrial. As the District Court later explained, one of the jurors

then sent an "unsolicited letter to the court" expressing the

sentiment    that    "the   total    case    .   .    .   seemed   unfair[,]

[u]njust[, and] [w]rong."       Spencer was, however, retried on the

same charges.       And, after a three-day trial, Spencer was found

guilty on both counts of the second superseding indictment and


     1 Morrison was initially charged together with Spencer, but
Morrison pleaded guilty to the three counts against him in the
first superseding indictment. The second superseding indictment
thus charged Spencer alone.


                                    - 4 -
sentenced to 60 months' imprisonment and 36 months' supervised

release.

                                       B.

             On May 14, 2015, several weeks after Spencer had been

convicted of these charges, he filed, pro se, what he styled as a

"Renewed Motion for a Required Finding of Not Guilty or, in the

Alternative, for a New Trial."          That motion claimed, among other

things, a Brady violation.           Specifically, Spencer contended that

the government had, in violation of Brady, failed to turn over

evidence regarding the prosecution's involvement in triggering a

correction    to   certain    erroneous       information      set    forth      on   a

certificate     that   had    been    issued     by    the   chemist       for    the

Massachusetts      State     Police    Laboratory       (the      “State      Police

Laboratory”)    who    was   responsible      for     analyzing      the   chemical

composition of a sample of the substance that the government

alleged Casallas had purchased from Morrison.

             The District Court denied Spencer's motion for a new

trial on October 8, 2015.              In doing so, the District Court

explained that, based on United States v. Del-Valle, 566 F.3d 31,

38 (1st Cir. 2009):

     [i]n the normal course, a defendant who seeks a new trial
     on the basis of newly discovered evidence must establish
     that: (1) the evidence was unknown or unavailable to the
     defendant at the time of trial; (2) failure to learn of
     the evidence was not due to lack of diligence by the
     defendant; (3) the evidence is material and not merely
     cumulative or impeaching; and (4) the emergence of the


                                      - 5 -
       evidence will probably result         in   an   acquittal   upon
       retrial of the defendant.

However, because the basis for Spencer's motion was "that the

government failed to disclose evidence required to be disclosed"

under Brady, the District Court -- quoting United States v.

González-González, 258 F.3d 16, 20 (1st Cir. 2001) -- explained

that    a   "more   defendant-friendly   .    .    .   standard    applies."

Specifically, the District Court noted that, as we held in United

States v. Flores-Rivera, 787 F.3d 1, 15-16 (1st Cir. 2015), with

respect to what a defendant must show when seeking a new trial

based on violation of Brady, "[i]nstead of requiring that the

defendant show that an acquittal would have 'probably' resulted

had the material been produced, we require only that the defendant

show a 'reasonable probability' that had the government disclosed

the evidence prior to trial, the result of the proceeding would

have been different."

            The District Court then applied this more "defendant-

friendly" test, under which Spencer's "threshold" burden was to

show that a Brady violation did, in fact, occur.          Accordingly, the

District Court used the three-prong test outlined by the Supreme

Court in Strickler v. Greene, 527 U.S. 263, 281-82 (1999), for

determining whether a Brady violation occurred.            As the District

Court explained, under Strickler, "[t]here are three components of

a true Brady violation: [1] [t]he evidence at issue must be




                                 - 6 -
favorable to the accused, either because it is exculpatory, or

because    it    is   impeaching;     [2]   that     evidence    must    have   been

suppressed by the State, either willfully or inadvertently; and

[3] prejudice must have ensued."               Id.      And, the District Court

further explained, relying on Kyles v. Whitley, 514 U.S. 419, 434

(1995), that, in order to show prejudice under Brady, the defendant

must demonstrate that the undisclosed evidence is material -- that

is, the defendant must show that there would be a "reasonable

probability of a different result" at trial had the evidence been

disclosed.

               The District Court concluded that, with respect to the

evidence concerning the prosecution's contacts with the chemist

for the State Police Laboratory that had not been disclosed by the

government, Spencer had succeeded in meeting his burden as to the

first two prongs of the test for finding a Brady violation set

forth in Strickler.        The District Court concluded, however, that,

"by the narrowest of margins," Spencer had not shown that he was

prejudiced by the government's withholding of the evidence -- that

is, that he had not shown that it was reasonably probable that the

outcome at trial would have been different had the evidence been

disclosed.       Accordingly, the District Court ruled that there had

been no Brady violation. And, because the District Court concluded

that   Spencer's      motion    --    although     it    also   referenced      other

issues    --    "focused   on   the    government's       failure   to   disclose"


                                       - 7 -
evidence   regarding    the    prosecution's   communications      with   the

chemist for the State Police Laboratory, the District Court denied

the motion.

           Spencer then filed this timely appeal, in which he

challenges four separate rulings below:            first, the District

Court's denial of his motion for a new trial under Brady on the

ground that the undisclosed evidence was not material; second, the

admission at trial of certain testimony from the two police

officers who organized and participated in the undercover drug

purchase that led to Spencer's arrest; third, the District Court's

refusal to declare a mistrial in consequence of certain statements

made by the prosecution during closing argument; and, finally, the

decision to deny Spencer discovery on his motion to dismiss the

case against him based on an allegation of vindictive prosecution.

We consider each challenge in turn.

                                    II.

           We   start   with    Spencer's   challenge   to   the   District

Court's ruling denying the motion for a new trial based on the

claimed Brady violation.       Spencer challenges only the third step

of the District Court's Brady analysis, concerning the materiality

of the undisclosed evidence, and thus we, too, focus on that issue.

For the reasons that follow, we reject Spencer's contention that

the District Court reversibly erred in denying Spencer's Brady-

based motion.


                                   - 8 -
                                      A.

           We have explained that, "[i]n Brady, the Supreme Court

held the Government's suppression of evidence favorable to the

accused violates due process where the evidence is material to

guilt or punishment."       Conley v. United States, 415 F.3d 183, 188

(1st Cir. 2005) (citing Brady, 373 U.S. at 87).                This materiality

prong of the Brady inquiry requires that the defendant show that

"there is a reasonable probability that, had the evidence been

disclosed, the result of the proceeding would have been different."

Turner v. United States, 137 S. Ct. 1885, 1893 (2017) (quoting

Cone v. Bell, 556 U.S. 449, 469-70 (2009)).

           As     the   Supreme   Court    emphasized     in    Strickler     with

respect   to    materiality,      "[t]he   question      is   not   whether   the

defendant would more likely than not have received a different

verdict with the evidence, but whether in its absence he received

a fair trial, understood as a trial resulting in a verdict worthy

of confidence."      527 U.S. at 264 (quoting Kyles, 514 U.S. at 434);

see also Turner, 137 S. Ct. at 1893 ("A reasonable probability of

a   different    result   is   one   in    which   the   suppressed    evidence

undermines confidence in the outcome of the trial." (citations

omitted)).      On the basis of this precedent, we have explained that

"[t]his somewhat delphic 'undermine confidence' formula suggests

that reversal might be warranted in some cases even if there is

less than an even chance that the evidence would produce an


                                     - 9 -
acquittal."       Flores-Rivera, 787 F.3d at 16 (quoting Conley, 415

F.3d at 188).

            We    review    the    District    Court's   denial    of   Spencer's

motion for a new trial on the basis of the government's alleged

Brady violation for abuse of discretion.             United States v. Cruz-

Feliciano, 786 F.3d 78, 87 (1st Cir. 2015).               Because, as we have

explained, the key issue concerns the materiality, under Brady, of

the undisclosed evidence, we are mindful in undertaking this review

that "the district court's determination on the materiality of

newly discovered evidence in prosecutorial nondisclosure cases is

ordinarily accorded deference," United States v. Sanchez, 917 F.2d

607, 618 (1st Cir. 1990) (citations omitted), "[d]ue to its

inherently fact-bound nature," id. (citation omitted); see also

United States v. Imbruglia, 617 F.2d 1, 7 (1st Cir. 1980) (noting

that the "district judge, who presided at appellant's trial,

reviewed appellant's newly discovered evidence and concluded it

did not justify the granting of a new trial" and concluding that

"[h]is assessment deserves regard").

                                        B.

            To assess the merits of the District Court's Brady ruling

as to materiality, we first need to set forth in more detail

exactly    what    the     District    Court    determined   the    undisclosed

evidence   was     and   how   the    government's   nondisclosure       of   that

evidence came to light.           And so we now turn to that task.


                                      - 10 -
            At trial, Spencer's attorney sought to draw the jury's

attention   to    the   fact   that    the     government   had    produced   two

different "certificates of drug analysis" that were prepared and

signed by Claire Rimkus, the chemist at the State Police Laboratory

who was responsible for analyzing the sample from the substance

that   Casallas    allegedly    had    purchased     from   Morrison.         Both

certificates were ultimately admitted into evidence.

            Each certificate stated that the sample "was found to

contain Cocaine . . . present in the base form."                  Moreover, each

certificate      identified    the    same   "agency   case   number"     (often

referred to as a "cc" or "control" number) that had been assigned

to the sample by the BPD.        That control number was 130164540.

            Officer Sean Flaherty -- the BPD officer responsible for

processing the substance alleged to be the cocaine base that

Casallas purchased from Morrison -- explained at trial that this

control number was generated by the BPD's "Computer Aided Dispatch

system" on March 20, 2013, once Flaherty had received the sample

from Keenan, and before Flaherty had completed the necessary intake

forms and placed the sample in a heat-sealed bag.                 Flaherty also

explained at trial that the purpose of assigning this control

number was to ensure that "every piece of evidence . . . is

tracked."

            The problem was that the first certificate of drug

analysis that Rimkus prepared, dated September 26, 2013, indicated


                                      - 11 -
that the "date of incident" associated with the sample was May 26,

2013.     That latter date was the date of Spencer's arrest.                    It was

not the date of the alleged transaction between Casallas, the

undercover officer, and Morrison, the co-defendant.                        The second

certificate was dated April 4, 2014.                  That certificate indicated

that the "date of incident" associated with the sample was March

20, 2013.       That date was the date of the alleged transaction.

             In light of the fact that there were two certificates,

and that only the latter one correctly stated the date of the

alleged    incident,      Spencer's       counsel      asked   Rimkus,     on    cross-

examination, about the discrepancy.               Rimkus responded that, after

she had prepared the first certificate, "it was discovered that

the Boston Police had essentially given [her] the wrong date of

the incident when they submitted the evidence."                   Rimkus explained

that she did not know the reason that the BPD had given her the

wrong    date    originally.       Rather,       she    explained,     she      "simply

receive[d] a drug evidence submission form [sometimes referred to

as an “SP-295” form] with suspect name, incident date, incident

number, and that is the information that [she] put on [her]

report."    Rimkus further testified that, with the new information

in hand, "[she] then prepared a corrected report," with "[t]he

only    difference    .   .   .   being    a    different      date   of   incident."

Accordingly,       Rimkus     testified        that    she     prepared    a     second




                                      - 12 -
certificate, dated April 4, 2014, which indicated that the correct

"date of incident" associated with the sample was March 20, 2013.

               On the basis of the fact that there were two certificates

setting       forth    different    dates    of     incident,    defense      counsel

contended in the closing argument to the jury that the government

had conducted a "sloppy investigation" and asserted that there

were "a whole host of reasons why you should not be persuaded

beyond a reasonable doubt that Barry Spencer is guilty of being a

dope dealer."         After the case had been submitted to the jury, the

jury    requested       a    "signed/notarized"       copy      of   the   April     4

certificate. "[N]o such copy was admitted into evidence," although

the    jury    did    have   a   copy   of   both   certificates,      just    not   a

"notarized copy of the corrected version." The jury then convicted

Spencer.

               Approximately two weeks later, on May 4, 2015, Spencer

filed, pro se, his motion for a new trial in which he raised the

Brady claim.          In that motion, Spencer asserted -- presumably on

the basis of Rimkus's testimony that "it was discovered that Boston

Police had essentially given [her] the wrong date of incident" --

that Rimkus "testified" at trial that she had "received a call and

was told to change the date [of incident]" on the certificate.

Spencer further asserted that the government, in violation of

Brady, had failed to disclose evidence that "could [have] been




                                        - 13 -
used to impeach . . . the caller who told Claire Rimkus to change

the date on the sample."

            On May 19, 2015, the District Court held a hearing on

that motion and on Spencer's separate motion to appear pro se at

that hearing and during sentencing.                   At the hearing, Spencer

(appearing pro se) again asserted that the government, in violation

of Brady, had not turned over evidence concerning a phone call

that Spencer alleged had been made to Rimkus instructing her to

change the date of incident on the lab certificate.

            In response to that assertion by Spencer, the Assistant

United     States    Attorney     ("AUSA")       in     charge      of   Spencer's

prosecution,      John    Wortmann,    revealed       that,   in    fact,    he   had

telephoned Rimkus on April 3, 2014, to inform her about the error

in the first certificate with respect to the date of incident.

Wortmann explained that Rimkus had no knowledge of the actual date

of incident and that Rimkus had simply relied on the BPD to supply

that information.        Specifically, Wortmann stated that "[t]he lab

doesn't    know   where    the   drugs   --    what    date   the    drugs   [were]

purchased.    They can't possibly know that.            And the clerical error

was committed when the drugs were submitted [by the BPD] to the

lab."     As a result, Wortmann stated that he had simply contacted

Rimkus to correct a "clerical error" on the drug certificate

"because the drug lab would have no basis for knowing one way or




                                      - 14 -
the other."      Wortmann suggested that he had also sent a follow-up

e-mail to the BPD after the phone call with Rimkus.

             The District Court deemed the government's failure to

disclose its "involvement in revising a key exhibit" "troubling."

On   June   4,    2015,   the   District      Court    sua    sponte     ordered    an

evidentiary hearing.        Two weeks later, the government produced a

"Case   Conversation      Log   Report"     that    had     not   previously      been

produced to Spencer in which, as the District Court highlighted,

"State Drug Lab employees, including Ms. Rimkus, recorded many .

. . of their conversations with the police and prosecutors."

             The evidentiary hearing took place on July 2, 2015.

During that hearing, Rimkus provided additional testimony.                        This

testimony,       the   District     Court     found,        "corroborat[ed]"       the

government's account of the contact between Wortmann and Rimkus,

in which Wortmann telephoned Rimkus to correct the incorrect date

of incident set forth on her initial certificate.                       The District

Court also noted that Rimkus testified that, after speaking with

Wortmann, Rimkus called the BPD's evidence unit to confirm the

incident date.

             Approximately      a   week    after     the    July   2    evidentiary

hearing,    on    July    10,   2015,   the    District       Court     ordered    the

government to produce the follow-up e-mail to the BPD that Wortmann

had testified at the May 19 hearing that he had sent to Rimkus.

The District Court ultimately found that, "[a]fter a thorough


                                     - 15 -
search of the AUSA's e-mails, the government concluded that he

misspoke and no such email exchange occurred."

                                       C.

            On the basis of the record that had been developed, the

District Court denied Spencer's Brady-based motion for a new trial.

The District Court identified two distinct types of evidence that

the government had failed to disclose -- (1) the State Police

Laboratory call log, and (2) other evidence, including the AUSA's

own testimony, concerning his "communications with Ms. Rimkus more

generally." The District Court concluded that, as to each category

of undisclosed evidence, the evidence was not material under the

standard articulated in Strickler and thus that Spencer's Brady

claim failed.

            The District Court began by addressing the government's

failure to turn over the call log.          The District Court stated that

this   evidence   of    the   prosecutor's        "close    involvement    in   the

Certificate's     preparation"    was,      per    the     first   prong   of   the

Strickler   test,      "favorable"    to    Spencer.         Specifically,      the

District Court concluded that had the call log been produced, the

fact that it "describes . . . Ms. Rimkus's entry for April 3, 2014

[that] indicates that the AUSA told her about a mistake on the

Certificate and where it came from . . . may well have called Ms.

Rimkus's conclusions into doubt."           That was so, the District Court

elaborated, particularly given "the jury's question about chain of


                                     - 16 -
custody, the proof of which depended largely on the documentation

implicated in the instant motion."

             The District Court also ruled in Spencer's favor as to

Strickler's second prong, which concerned whether evidence of the

call   log's    existence      was   suppressed,     either     willfully     or

inadvertently, by the government.             In this regard, the District

Court concluded that, although the United States Attorney's Office

was not aware that the State Police Laboratory had a practice of

logging calls from prosecutors, Rimkus was nevertheless "part of

the prosecution team."       As a result, "because [Rimkus] knew about

the call log well in advance of Mr. Spencer's first trial, the

government's 'we didn't know' excuse for failing to produce it to

the defense fails."

             But, in considering the final, prejudice prong of the

Strickler analysis, the District Court ruled against Spencer,

though "only by the narrowest of margins."                 The District Court

explained that, "[a]t trial, the government presented evidence

that   the   alleged   drugs    purchased     from   Mr.    Morrison,   in   the

transaction    where   Mr.     Spencer   stood    watch,    were   assigned    a

control . . . number by the [BPD]."               And, the District Court

explained, "[t]he evidence showed that the sample bearing [that]

control number was sent to Ms. Rimkus at the State Drug Lab, and

that she analyzed the sample bearing that control number in

preparing her original Drug Analysis Report."               As a result, the


                                     - 17 -
District Court emphasized that, regardless of any error by the BPD

concerning the date of incident on the first form, the "control

number associates the sample purchased from Mr. Morrison on March

20, 2013 with the sample that tested positive for crack cocaine at

the lab."

             Based on this reasoning, the District Court rejected

Spencer's contention that there was a reasonable probability that

the call log, had it been disclosed, would have been sufficient to

undermine confidence in the jury's verdict.               As the District Court

put it, "no reasonable jury could have concluded, in light of the

control number records, that the chain of custody was broken."

For   that     reason,    the     District       Court    concluded     that   the

"government's failure to produce the call log . . . [,] while

questionable, was not an actionable Brady violation."

             The   District     Court    then    turned   to    the   government's

failure   to   disclose    additional       evidence      regarding    Wortmann's

communications with Rimkus that might have shed further light on

the nature and extent of Wortmann's intervention.                 This additional

evidence included firsthand accounts of the conversation between

Wortmann and Rimkus, such as the one that Wortmann provided during

the May 19 hearing before the District Court.                  The District Court

concluded that this evidence, too, was favorable to Spencer, as it

"might have been used to paint Ms. Rimkus as sloppy, at best, or

a pawn of the prosecution, at worst."             Likewise, "because the AUSA


                                        - 18 -
himself was involved" in his communications with Rimkus "and

necessarily knew they happened," the District Court concluded that

the   government     willfully   suppressed     this    evidence    concerning

Wortmann's communications with Rimkus.

             Nevertheless,   turning      to    the    third    prong   of   the

Strickler test, which concerns the materiality aspect of Brady,

the District Court ruled against Spencer. The District Court again

emphasized     the    importance   of     the    fact    that    the    control

number -- common to both the initial certificate (which had the

wrong date of incident) and the corrected certificate (which had

the right date of incident) -- matched the sample Rimkus analyzed

to the substance obtained during Casallas's undercover purchase.

Because "government counsel could have relied only upon the control

number to show the chain of custody and integrity of Ms. Rimkus's

test results[, n]o reasonable jury could have doubted that the

sample delivered to Ms. Rimkus was the same one purchased from Mr.

Morrison on March 20, 2013."

                                     D.

             Spencer contends, in challenging the Brady ruling below,

that the undisclosed evidence -- whether considered individually

or in combination -- would have enabled him to "cast doubt" on the

link between Spencer and the sample Rimkus determined contained

cocaine base.        Spencer further contends that the disclosure of

this evidence at trial would have rendered a different outcome


                                   - 19 -
reasonably probable. Spencer thus contends that the District Court

abused its discretion in denying his motion for a new trial on the

ground that the undisclosed evidence was not material within the

meaning of the third prong of the Strickler test for identifying

a Brady violation.

            In    support   of    that   contention,   Spencer   makes    the

following points.        Spencer contends that the withheld evidence

would have enabled him to "establish a lack of confidence" in the

jury's verdict by sowing doubt as to whether the sample Rimkus

tested    was    taken   from   the   substance   Casallas   purchased   from

Morrison on March 20.           In this regard, Spencer argues that the

District Court wrongly relied on the "infallibility" of the control

number.     On Spencer's account, by showing the role that the

prosecutor played in getting Rimkus to change the date of incident,

the withheld evidence "could have shown the possibility that [the

control number] was incorrect or even manufactured as well."

Spencer also emphasizes the District Court's statement -- with

respect to the second Strickler prong -- that the withheld evidence

might have "been used to paint Ms. Rimkus as sloppy, at best, or

a pawn of the prosecution, at worst."

            In further support of his materiality argument, Spencer

contends that the withheld evidence must be considered in light of

a number of background features of the case.            Spencer points, in

particular, to Rimkus's relative inexperience, the time lag before


                                      - 20 -
the submission of the sample by the BPD to the State Police

Laboratory, and an additional error on the form that the BPD used

to submit evidence to the State Police Laboratory, which concerned

how the sample had been obtained by the BPD.2 And, Spencer contends

that his case is closely analogous to Flores-Rivera.           There, we

overturned    a   district   court's   conclusion,   under   Brady,   that

certain undisclosed evidence was not material.          787 F.3d at 20.

Finally, Spencer notes, his first trial ended in a mistrial, with

one of the jurors expressing significant unease with the case

against Spencer.      On this basis, Spencer argues that, had that

first jury known of the undisclosed evidence, "there would have

been a 'reasonable probability' of an acquittal."

                                   E.

             No doubt, Spencer could have seized on the evidence that

Wortmann contacted Rimkus and had her correct one aspect of the

certificate that she prepared -- the date of incident -- to suggest

that the control number was "incorrect or even manufactured." But,

we do not see what basis we have on this record for second-guessing

the trial judge's conclusion about whether the lost opportunity to


     2 The BPD submitted the substance to the State Police
Laboratory for analysis on September 17, 2013, approximately six
months after Casallas made the purchase from Morrison.          In
addition, as the District Court noted, the submission form used by
the BPD to submit the sample for analysis to the State Police
Laboratory wrongly indicated that the "sample was the result of a
'[s]eizure'" rather than a "'purchase,' which was another option
on the form."


                                 - 21 -
make   that    suggestion   to   the    jury   renders   the   nondisclosure

material.     See Flores-Rivera, 787 F.3d at 17 (noting that "[w]e do

not . . . automatically require a new trial whenever a combing of

the prosecutors' files after the trial has disclosed evidence

possibly useful to the defense but not likely to have changed the

verdict"      (quoting United States v. Dumas, 207 F.3d 11, 15 (1st

Cir. 2000) (alterations in original)).

              As we have explained, the undisclosed evidence shows no

more than that Wortmann contacted Rimkus on April 3, 2014, in order

to correct the date of incident on Rimkus's certificate of drug

analysis.        But, the record shows that it was a BPD officer,

Flaherty, who, much earlier, on March 20, 2013, assigned a control

number to the substance that Flaherty had received from another

BPD officer, Keenan, and that the same control number that Flaherty

had assigned was on the sample that Rimkus analyzed.            In addition,

the record shows that Rimkus relied, in preparing her certificates

of drug analysis, on an error on the SP-295 form that the BPD used

to submit evidence to the State Police Laboratory.               The record

does not show that Rimkus relied on any materials that the BPD

prepared    in    the   course   of   initially   processing    and   logging

Casallas's undercover purchase.          In light of these aspects of the

record, the District Court could reasonably conclude that the fact

of the prosecutor's contact with Rimkus to correct the error

regarding the date of incident on the initial certificate would


                                      - 22 -
provide no more than a speculative basis for a conclusion that the

control number itself was "incorrect or even manufactured."

              We also conclude that it was reasonable for the District

Court    to   conclude   that,   even   if   the   control   number   was   not

"incorrect or even manufactured," the undisclosed evidence does

not suffice to cast doubt on whether Rimkus, due to her alleged

sloppiness or her ties to the prosecution, tested the wrong sample.

Spencer does not dispute, after all, that Rimkus conducted her

own, independent analysis of the substance that she then determined

was cocaine base.        And, nothing about the undisclosed evidence

shows Rimkus to be sloppy or unprofessional in her work as a

chemist for the State Police Laboratory.            Rather, the undisclosed

evidence just shows that Rimkus corrected erroneous information

that had been given to her and that she had no reason to know was

wrong.    As a result, Spencer can only speculate that the substance

that Casallas purchased from Morrison was "removed or changed

between March 20, 2013, and September 2013 when it was allegedly

tested by Ms. Rimkus."

              We thus conclude that the District Court did not abuse

its discretion, as it reasonably determined that the withheld

evidence did not generate a reasonable probability of a different

outcome at trial by calling into question the "chain of custody"

of the sample or the "integrity of Ms. Rimkus's test results."

And this conclusion is consistent with Flores-Rivera.


                                   - 23 -
            The undisclosed evidence in that case consisted of (1)

a letter to the prosecutor from the star witness to the crimes,

and   (2)   notes    that   the   star   witness    had   made   concerning

conversations he had had with two other cooperators while all three

were in prison.      We explained that the notes, which directly cast

doubt on the star witness's testimony regarding whether he had

coordinated   with    the   other   witnesses,     constituted   the   "only

evidence that would have eliminated the claim that the testimony

[of the star witness and the other two cooperators] was entirely

uncoordinated," and that the letter to the prosecutor "would have

provided a uniquely colorful tool for both attacking [the star

witness's] motivation and raising the prospect that [he] and the

prosecutor were hiding something from the jury."            Flores-Rivera,

787 F.3d at 20.

            The undisclosed evidence in this case, however, does not

cast doubt in any similarly direct way on any similarly key

representation.       As we have noted, Rimkus explained that she

corrected the first certificate because "it was discovered" that

the first certificate was wrong with respect to the date of

incident on that certificate. But, the undisclosed evidence in no

way undermines that representation.          And, similarly, it is not

clear how the undisclosed evidence casts meaningful (as opposed to

merely speculative) doubt on the credibility of any other witness




                                    - 24 -
who testified about any aspect of the case that bears on the

integrity of the control number.

            Moreover,   while   the   testimony   of   the   cooperating

witnesses in Flores-Rivera that could have been undermined by the

undisclosed evidence was "both essential to the convictions and

uncorroborated by any significant independent evidence," id. at

18, Rimkus's testimony was not similarly uncorroborated.        Rather,

her testimony was supported by Casallas's and Keenan's testimony

concerning the undercover drug purchase, Flaherty's testimony

concerning the BPD's intake process, and the documentary evidence

that indicated that the date of incident on the SP-295 form used

by the BPD to submit the sample for analysis to the State Police

Laboratory contained the error as to the date of incident that was

then reproduced on Rimkus's initial certificate of drug analysis.

Additionally, at both the trial and the evidentiary hearing on

Spencer's Brady-based motion, Rimkus's testimony, although phrased

in a manner that omitted mention of the AUSA's involvement, was

consistent with Wortmann's.

            To be sure, the District Court did state that the

question of prejudice from the non-disclosure failed "only by the

narrowest of margins."    And Spencer was being retried following a

mistrial.    But, a district court receives no less deference in a

close case than in a clear-cut one.       In fact, it is in the close

case that the fact that our review is for abuse of discretion


                                 - 25 -
matters most.   We also agree with the government that it is hard

to conclude anything about what might have been in the mind of

Spencer's first jury -- let alone Spencer's second jury -- from

the fact of the initial mistrial alone.      Thus, the fact that

Spencer was being retried does not, at least on this record, lead

us to conclude that we must substitute our own judgment for that

of the District Court as to the resolution of what the District

Court determined was a close call.3

                               III.

          Spencer makes three additional challenges on appeal.   We

consider, and reject, each in turn.

                                A.

          Spencer contends, first, that the District Court erred

in admitting certain testimony from both Keenan and Casallas that

Spencer argues was unduly prejudicial to him.   In challenging the



     3 Spencer separately contends that his trial counsel provided
ineffective assistance because he did not move for a mistrial or
perhaps a voir dire of Rimkus after she testified.      But, "[w]e
have held with a regularity bordering on the monotonous that
ineffective assistance of counsel claims, which require a showing
of deficient attorney performance and prejudice to the defendant,
must originally be presented to, and acted upon by, the trial
court . . . because an appellate court usually is ill-equipped to
handle the fact-specific inquiry that such claims often require."
United States v. Ofray-Campos, 534 F.3d 1, 34 (1st Cir. 2008)
(citations omitted). Spencer presents no developed argument as to
how, in his words, "counsel's failures in this regard are [so]
manifestly apparent from the record" such that we should depart
from this "well-settled rule," id., and so we do not consider his
ineffective assistance claim.


                              - 26 -
decision to allow these portions of testimony at trial, Spencer

contends that Keenan and Casallas were "fact witness[es] entitled

to testify as to what [they] observed Spencer doing," rather than

qualified experts under Rule 702 of the Federal Rules of Evidence,

who would have been permitted to contextualize Spencer's behavior

in light of their professional experience.4         In consequence,

Spencer argues that he was prejudiced by the admission of the

portions of Keenan's and Casallas's trial testimony in which they

testified not merely to what they observed during the incident but

to their own views as to why, in light of their experience, what

they observed evidenced the committing of a "tandem" drug crime.

Thus, Spencer contends that these portions of testimony were

"improperly admitted under Rule 403" of the Federal Rules of

Evidence.5

             With respect to Keenan's testimony, Spencer notes that,

when asked whether, based on Keenan's "training and experience,"

it was "unusual for drug dealers to work in tandem out on the

street," Keenan responded that it was not, in fact, unusual.   And,


     4 Rule 702 provides that "[a] witness who is qualified as an
expert by knowledge, skill, experience, training, or education may
testify in the form of an opinion or otherwise" under certain
specified conditions. Fed. R. Evid. 702.
     5 Rule 403 provides that the trial "court may exclude relevant
evidence if its probative value is substantially outweighed by a
danger of one or more of the following: unfair prejudice, confusing
the issues, misleading the jury, undue delay, wasting time, or
needlessly presenting cumulative evidence." Fed. R. Evid. 403.


                                - 27 -
Spencer points out, Keenan then elaborated: "[t]hey often do it

because . . . one guy may go out and gather the customers up while

the person having the drugs doesn't have to expose himself as

much."

             With respect to Casallas's testimony, Spencer highlights

the portion in which Casallas stated that he approached Spencer

and "asked him if he was on" and then explained that being "on" is

"street terminology usually used by drug users and drug dealers to

determine whether the person is actually selling drugs."            Spencer

also objects to Casallas's testimony in which Casallas stated that

Spencer was "scanning the area, looking at cars as they drove by,"

and   then   explained   that   he   believed,   on   the   basis   of   his

experience, that Spencer was "doing counter-surveillance."

             Even assuming, however, favorably to Spencer, that our

review of the District Court's evidentiary rulings with respect to

the challenged testimony is for abuse of discretion, United States

v. Dunston, 851 F.3d 91, 96 (1st Cir. 2017), we see none here.6


      6At trial, Spencer's counsel objected to Keenan's testimony
as follows: "Objection, your Honor.     Relevance."   The District
Court then overruled the objection.      Later, Spencer's counsel
objected to the first portion of Casallas's testimony that he now
challenges on appeal without specifying a basis for the objection,
and was again overruled.    Spencer's counsel did not object to
Casallas's testimony that Spencer was performing "counter-
surveillance, although Spencer's counsel did object to Casallas's
explanation of what Casallas meant by the term "counter-
surveillance," and the District Court sustained that objection.
The government contends on this basis that Spencer's challenges to
the District Court's admission of these portions of Keenan's and


                                 - 28 -
We have previously explained that opinion testimony by a witness

who has not been qualified as an expert witness under Rule 702 may

nevertheless be admissible under Rule 701 of the Federal Rules of

Evidence provided that such testimony is "'rationally based on the

perception     of    the     witness,'      [is]        'helpful      to    .    .   .   the

determination       of   a   fact    in    issue,'       and   [is]     'not     based   on

scientific, technical, or other specialized knowledge within the

scope of Rule 702.'"            United States v. Santiago, 560 F.3d 62, 66

(1st Cir. 2009) (second alteration in original) (quoting Fed. R.

Evid. 701).    We have explained further that the touchstone for the

admissibility under Rule 701 of such lay-opinion testimony is

whether the testimony has the "potential to help the jury." United

States v. Albertelli, 687 F.3d 439, 447 (1st Cir. 2012).

             Under       this      standard,       we     have     deemed        testimony

inadmissible    "when        the    jury   can     readily       draw      the   necessary

inferences and conclusions without the aid of the opinion." United

States v. Etienne, 772 F.3d 907, 919 (1st Cir. 2014) (emphasis in

original) (citations omitted). We have also explained that helpful

testimony is typically "based on the lay expertise a witness

personally acquires through experience, often on the job."                           United



Casallas's testimony may be reviewed only for plain error. Because
we conclude that the testimony is admissible even on the more
defendant-friendly abuse-of-discretion standard, we need not
decide whether Spencer's counsel's objections were sufficient to
preserve the arguments he asks us to accept.


                                          - 29 -
States v. Vega, 813 F.3d 386, 394 (1st Cir. 2016) (quoting United

States v. Maher, 454 F.3d 13, 24 (1st Cir. 2006)); see also United

States v. Ayala-Pizarro, 407 F.3d 25, 28-29 (1st Cir. 2005).                   And,

we have noted that "a police officer noticing patterns of behavior

across criminal operations uses straightforward logic to conclude

a defendant's behavior fits within that pattern and thus, does not

need to be qualified as an expert."               Vega, 813 F.3d at 394.

             Accordingly, we have upheld district court decisions to

admit, under Rule 701, testimony from police officers "translating

jargon common among criminals," even though not "traditional" lay

testimony.    Albertelli, 687 F.3d at 446-47; see also Dunston, 851

F.3d at 96 (noting that "[a]pplication of Rule 701 in the drug-

trafficking     context    is     not    novel:    'we   have    long   held   that

government witnesses with experience in drug investigations may

explain   the    drug     trade    and     translate     coded    language'     for

factfinders through lay opinion testimony" (quoting United States

v. Rosado-Pérez, 605 F.3d 48, 56 (1st Cir. 2010))).

             Applying these principles here, we conclude that the

District Court did not abuse its discretion in admitting the

objected-to testimony of either Keenan or Casallas, who, we note,

were both available for cross-examination by Spencer.                   See Vega,

813 F.3d at 394.          The record supportably reflects that both

officers provided testimony about their observations of Spencer's

behavior based on their accumulated experience as police officers


                                        - 30 -
who have handled many drug cases.          United States v. Valdivia, 680

F.3d 33, 50-51 (1st Cir. 2012); see also Ayala-Pizarro, 407 F.3d

at    28    (admitting    certain     testimony   "about    how    drug    points

operate . . . because it was based on particularized knowledge

that the witness had by virtue of his position as a police officer

assigned to patrol the neighborhood" (citation and alterations

omitted).           Specifically,     Casallas    testified       that    he     had

"personally purchased successfully over 100 undercover drug buys"

during his nine years as a member of the BPD's Drug Control Unit,

while      Keenan    testified   that    he,   too,   had   spent    ten       years

"exclusively as a drug investigator," including as an undercover

officer.

              Moreover, the record supportably shows that Keenan's and

Casallas's testimony was helpful to the jury in interpreting

Spencer's actions and statements.          Casallas and Morrison testified

about certain patterns of conduct and speech that they, on the

basis of their experience, believed to be typical of those engaged

in selling drugs.        That testimony included the fact that Spencer

and Morrison were working as a team, the meaning of being "on,"

and   Spencer's      behavior    while   Casallas     and   Morrison      actually

executed the transaction.           Thus, as in Valdivia, we conclude that

the challenged "testimony was not so obviously within the jury's

bounds of knowledge as to negate all probative value."                   680 F.3d

at 51.


                                      - 31 -
                                     B.

           Spencer separately contends that the prejudice to him

from the District Court's admission of the challenged testimony

from Keenan and Casallas "was compounded by improper comments of

the prosecutor in his opening and closing statements," during which

the prosecutor four times referred to Spencer as a "drug dealer"

and thus (in Spencer's view) improperly suggested that Spencer

"had a propensity to deal drugs."         Because Spencer did not object

to these statements, our review is for plain error.          United States

v. Acosta-Colón, 741 F.3d 179, 198-99 (1st Cir. 2013).                 Thus,

Spencer must show that "(1) an error occurred (2) which was clear

or   obvious   and   which   not   only   (3)   affected   the   defendant's

substantial rights, but also (4) seriously impaired the fairness,

integrity, or public reputation of [the] proceedings."                United

States v. Kasenge, 660 F.3d 537, 541 (1st Cir. 2011) (quoting

United States v. Duarte, 246 F.3d 56, 60 (1st Cir. 2001)).

           Spencer, however, cannot show the requisite prejudice

from the remarks, see United States v. Kinsella, 622 F.3d 75, 84

(1st Cir. 2010) (on plain-error review, a defendant challenging a

prosecutor's remarks as improper must "show[] both error and

prejudice"), even were we to assume that the prosecutor's remarks

rise to the level of a clear or obvious error.              But see United

States v. Wiley, 29 F.3d 345, 351 (8th Cir. 1994) (concluding that

a prosecutor's remarks during closing argument, which referred to


                                   - 32 -
the defendant as someone engaged in the "business [of] dealing

drugs,"   "did     not     deprive     [the     defendant]     of     a     fair

trial . . . because the jury already was aware that [the defendant]

was on trial for distribution of cocaine base"); cf. United States

v. Marr, 760 F.3d 733, 742-43 (7th Cir. 2014) (rejecting on plain-

error review a defendant's challenge to a prosecutor's comments to

the jury during closing argument, in which the prosecutor referred

to certain transactions at issue in the case "and asked, 'what

legitimate business does that?          What legitimate business writes

$1.3 million to cash and to a currency exchange?'" on the basis

that the prosecutor's comments constituted "reasonable inferences

from the evidence adduced at trial").

          For     one     thing,     "the     fact   that    there    was     no

contemporaneous         objection      or       request      for     curative

instructions . . . depriv[ed] the district judge of the opportunity

to provide special or additional instructions with regards to the

closing statements."      United States v. Castro-Davis, 612 F.3d 53,

68 (1st Cir. 2010). For another, the District Court did explicitly

instruct the jury that the arguments made to the jury during

opening and closing argument by attorneys for the prosecution and

defense were not evidence, and that the members of the jury "are

the first and only judges of the facts in this case."              In light of

our long-standing presumption that jurors follow instructions,

United States v. Ponzo, 853 F.3d 558, 584 (1st Cir. 2017), and


                                    - 33 -
against the backdrop of "the evidence presented at trial from

multiple witnesses," "any potentially harmful effect from the

prosecutor's closing was safeguarded by the district court's final

jury instructions," Castro-Davis, 612 F.3d at 68 (citing United

States v. Mejía-Lozano, 829 F.2d 268, 274 (1st Cir. 1987)).

                                   C.

          Finally,   Spencer     takes    aim   at   the   ruling   by   the

Magistrate Judge responsible for presiding over the initial phase

of Spencer's case in which the Magistrate Judge denied Spencer's

request   for   discovery   on   his     vindictive-prosecution     claim.

Spencer agrees with the government that a defendant must "advance

some evidence tending to establish [a] vindictive-prosecution

claim" before he can obtain discovery.          United States v. Bucci,

582 F.3d 108, 113 (1st Cir. 2009).          Spencer, however, contends

that he satisfied this standard and thus that the Magistrate Judge

erred in denying Spencer discovery.        Specifically, Spencer points

to the fact that he provided evidence that he filed a civil suit

against Keenan in 2006 for assault and unlawful search and arrest,

and that "grand jury testimony" showed that "Keenan . . . directed

[Casallas] to approach Mr. Spencer on March 20, 2013," and thus

"singled [Spencer] out" for arrest.       Spencer further contends that

the government's alleged Brady violation constitutes additional

evidence tending to show a vindictive prosecution, "lend[ing]




                                 - 34 -
credence       to    [Spencer's]        allegations       that    he   was    specifically

targeted for federal prosecution based on his prior lawsuit."

               Our review of the Magistrate Judge's ruling is for abuse

of discretion.            Id. at 114.      We find none.

               Spencer       concedes        that    he        bears    the       burden    of

"connect[ing] any vindictive animus to those making the challenged

charging decision in his case."                     Id. (citation omitted).                The

government, however, emphasizes that, from all that the record

shows,    federal         authorities       were    unaware      of    Spencer's      lawsuit

against Keenan when they agreed to take Spencer's case from the

Suffolk County District Attorney's Office.                       And Spencer points to

nothing in the record that would tend to show the contrary -- let

alone that Spencer's lawsuit against Keenan motivated federal

authorities          to   agree    to    prosecute     Spencer.             Instead,   tying

Spencer's Brady claim to his vindictive prosecution claim, Spencer

offers        only    speculation,         suggesting          that    it    is     otherwise

"inexplicable" that federal authorities would first have sought to

try him, and later to withhold evidence from him.                                  But, such

speculation is plainly insufficient to satisfy the standard we

laid out in Bucci. Id. at 114 ("To obtain discovery, [a defendant]

must     do    more       than    simply    identify       a     potential        motive   for

prosecutorial animus."             (citation omitted)).

               Moreover,         although    the     government        admits       that   the

particular drug transaction at issue in this case involved a small


                                            - 35 -
quantity of cocaine base, the government notes that Wortmann stated

in an affidavit -- and Spencer does not dispute -- that Spencer

had "close to 100 entries on his Board of Probation Records" and

had been "convicted of approximately 19 crimes going back to 1990."

It is thus not inexplicable that federal authorities took Spencer's

case.7

          For all of these reasons, Spencer's challenge regarding

his vindictive prosecution claim fails.

                               IV.

          For the foregoing reasons, we affirm the rulings below.




     7 We note, too, as Spencer acknowledges, that the relevant
undisclosed evidence was not available to the Magistrate Judge at
the time of the Magistrate Judge's ruling on Spencer's discovery
request, and Spencer never sought to renew his motion.


                              - 36 -
