March 11, 1993
               UNITED STATES COURT OF APPEALS
                   FOR THE FIRST CIRCUIT
                                        

No. 91-1286

                       UNITED STATES,

                         Appellee,

                             v.

                   VICTOR MANUEL ALVAREZ,

                   Defendant, Appellant.

                                        

No. 91-1287

                       UNITED STATES,

                         Appellee,

                             v.

                        DIANA MATOS,

                   Defendant, Appellant.

                                        

       APPEALS FROM THE UNITED STATES DISTRICT COURT

              FOR THE DISTRICT OF PUERTO RICO

        [Hon. Carmen C. Cerezo, U.S. District Judge]
                                                   

                                        

                           Before

                  Torruella, Circuit Judge,
                                          
              Campbell, Senior Circuit Judge,
                                            
            and Skinner,* Senior District Judge.
                                               

                                        

Rachel  Brill,  Assistant   Federal  Public  Defender,  with  whom
            
Benicio  Sanchez Rivera,  Federal Public  Defender, was  on brief  for
                  
appellant Victor Manuel Alvarez.
Joseph C.  Laws, Jr., by Appointment  of the  Court, for appellant
                   
Diana Matos.
Ivan  Dominguez,  Assistant  United  States  Attorney,  with  whom
              
Daniel  F. Lopez  Romo, United  States Attorney,  and Jose  A. Quiles-
                                                                 
Espinosa, Senior Litigation Counsel, were on brief for appellee United
   
States.

                                        

                       March 11, 1993
                                        

                

*Of the District of Massachusetts, sitting by designation.

SKINNER, District Judge. 
                       

       Appellants Victor M. Alvarez and  Diana Matos, common

law  husband and  wife,  were convicted  by  a jury  in  the

District of Puerto Rico for aiding and abetting several drug

offenses.1    Miguel Flores,  though  not  a party  to  this

appeal nor  convicted in the  same trial,  played a  central

role in  the alleged cocaine trafficking  scheme and pleaded

guilty  to  the  identical  charges.    Appellants  defended

against  the  charges  alleging  that  they  were  unwitting

participants  in  defendant   Flores'  cocaine   trafficking

scheme.  Flores  offered testimony  to the same  end.   Each

appellant advances numerous grounds for reversal.  

       Appellant  Alvarez  appeals his  convictions alleging

that the  district court  (1) erroneously refused  to accept

defendant Flores' guilty plea prior to the trial  of Alvarez

and Matos,  (2) improperly prohibited Flores from testifying

that  his testimony  exposed him  to criminal  penalties for

cocaine trafficking, and (3)  errored in denying appellant's

                    

1 Alvarez  and Matos were  convicted for  the possession  of
cocaine  with intent to distribute in violation of 18 U.S.C.
   2 and 21 U.S.C.    841(a)(1); the  importation of cocaine
into the customs territory of the United States in violation
of 18 U.S.C.    2 and 21 U.S.C.   952(a); and the failure to
declare  cocaine in the cargo manifest or supply list of the
aircraft which  brought them  into the customs  territory of
the  United States  in violation  of 18  U.S.C.    2 and  21
U.S.C.   955.  

                            -3-
                             3

motion for judgment of acquittal.  We affirm with respect to

Alvarez.

       Appellant Matos  joins the arguments  of Alvarez  and

further appeals her convictions,  alleging that the district

court  failed  to  exclude  government   evidence  that  was

produced in violation of Rule 16, Federal Rules  of Criminal

Procedure.   As  to  Matos, we  reverse  and remand  to  the

district court for a new trial.

I.     Evidence
               

       We recite  the evidence in  the light most  favorable

to the  prosecution.   United States  v. Campbell,  874 F.2d
                                                 

838,  839  (1st Cir.  1989).   The  evidence showed  that on

December 8, 1989, Victor M. Alvarez, Diana Matos, and Miguel

A.  Flores arrived  at  the Luis  Munoz Marin  International

Airport, San Juan, Puerto  Rico, on American Airlines flight

904  from Caracas,  Venezuela.   A  U.S. Customs  Inspector,

Francis Aponte, noticed that  the three individuals appeared

to be nervous and were talking secretively among themselves.

Inspector  Aponte approached  the individuals,  made routine

inquiries of them,  and referred the group  to the secondary

inspection station (a table used to examine the contents  of

a passenger's luggage).  At that time, appellant Alvarez was

                            -4-
                             4

permitted   to  leave  the  customs  enclosure  to  purchase

airplane tickets to New  York for each member of  the group.

Inspector Aponte testified on  cross-examination that he had

not  made  any  written  record of  the  group's  suspicious

behavior  even though  such information  would have  been an

important part of the case report. 

       Carlos  Ortiz,   also  a   U.S.  Customs   Inspector,

testified  that he noticed two individuals, later identified

as Flores and  Matos, pushing two carts stacked with luggage

and  that  he motioned  for them  to approach  his secondary

station.    Inspector  Ortiz requested  Matos'  and  Flores'

customs declaration cards,  noting that both cards  appeared

to  have  been  filled  out  by  the  same  person.    Matos

complained that  the airline had  broken a bottle  of liquor

that she packed in  her suitcase.  During his search  of the

luggage, Ortiz noticed that the luggage contained both men's

and women's  clothing and  he discovered a  heavy, newspaper

wrapped  package.   Ortiz unwrapped  the package to  find an

aged  painting of  a young  girl in a  wooden frame.   Ortiz

asked Matos if she had purchased the picture on her trip, to

which she answered "yes."  

       Inspector Ortiz  consulted with  a senior  inspector,

took  the picture  to a  search room,  and drilled  into the

                            -5-
                             5

picture frame using a  small drill bit.  Ortiz  discovered a

white  powdery substance  inside the  wooden frame,  which a

field test  indicated was  cocaine.   Matos and  Flores were

arrested  and searched.    Customs  inspectors then  located

Alvarez in the airport's main concourse and placed him under

arrest.    Inspectors conducted  a  thorough  search of  the

group's  luggage,  finding  two  additional  paintings  that

concealed cocaine  and discovering false bottoms  in each of

the  six suitcases  that  also concealed  cocaine.   Customs

agents  determined  that the  group  carried  more than  ten

kilograms of cocaine.

        A grand  jury returned a  three count indictment  on

January 3,  1990, against Matos, Alvarez, and  Flores.  Each

defendant pleaded  not guilty.   On October 2,  1990, Flores

filed  a  notice  to  plead  guilty  on  one  count  of  the

indictment.   It appears,  however, that Flores  intended to

plead guilty on all three counts, and on October 5, 1990, he

amended his petition accordingly.   On October 5, 1990,  the

district   court   extensively   questioned  Flores   before

declining  to accept his plea.  Flores asserted that Alvarez

and Matos had been unaware of any plan to import cocaine and

that he, himself, was solely responsible for the crime.  The

judge  suspended  the  proceeding  because  she  was  unsure

                            -6-
                             6

whether Flores could plead  guilty to aiding and  abetting a

crime while  simultaneously proclaiming the innocence of the

other alleged participants.

       On October 9, 1990, the Flores plea hearing  resumed.

The judge explained that  Flores' refusal to acknowledge the

aiding  and abetting  modality did  not preclude  his guilty

plea.   The court then engaged in an extensive colloquy with

defendant Flores in accordance  with Rule 11 of the  Fed. R.

Crim. P.   The judge  noted that Flores  had proclaimed  the

innocence of Alvarez and Matos in a confidential letter that

Flores had  written  to  the  judge  from  prison.    Flores

confirmed sending the  letter and explained that  appellants

were friends  of his  from  New York,  the home  of all  the

parties.  Flores  had invited  appellants to join  him on  a

cruise from San Juan to several caribbean islands, including

a stop in Caracas,  Venezuela.  While on the  cruise, Flores

met  a man who offered  him three thousand  dollars to bring

several  pictures from  Venezuela  to Puerto  Rico.   Flores

agreed to  meet the man at  a hotel in Caracas  and to carry

the pictures into Puerto Rico as a passenger on a commercial

airline.   Flores  did  not tell  Alvarez  or Matos  of  his

scheme.  

                            -7-
                             7

       Flores, Alvarez,  and Matos  left the  ship while  it

was in  port in Caracas to visit  the beach.  Flores claimed

to  have  tricked the  appellants  into  missing the  ship's

scheduled departure because he did not want to fly to Puerto

Rico alone.  After missing the ship, Flores took Alvarez and

Matos to the predesignated hotel, checked the group into two

rooms, secretly picked up the pictures, and borrowed several

pieces  of luggage from  the man  after explaining  that the

group  had left  their  bags on  the  cruise ship.    Flores

arranged to meet the man in Puerto Rico at which time Flores

would deliver the pictures  and return the borrowed luggage.

Flores  claimed that he never  saw the cocaine  or even knew

for certain  that he  was carrying cocaine,2  but "imagined"

that the  frames concealed cocaine because  "nobody is going

to pay you  three thousand  dollars just to  bring in  three

pictures."   Flores  also denied  knowing that  the borrowed

suitcases concealed cocaine.  Flores explained that Alvarez,

Matos, and  he purchased  new cloths  in  Caracas and  spent

several days in the  hotel before returning to  Puerto Rico.

Flores  packed  the  three  pictures in  separate  bags  and

                    

2 Flores explained to the  judge, "At no time did  [the man]
tell me  it was cocaine.   He told  me, `I want  you to take
these pictures  for me.   Take  them there.'   He  says, `it
doesn't contain anything dangerous.'"

                            -8-
                             8

covered them with cloths.  Flores maintained that appellants

were totally  unaware of  his trafficking scheme  during the

entire trip.

       The district court declined Flores' plea, stating: 

       Now, you have stated that you  did not know what  was
       in the picture frames, you did  not know what was  in
       any of the luggage that you  carried.  That in itself
       carries with it a defense  that you could  present to
       the jury.   So I am  not convinced that you have made
       a  plea of  guilty that  I  could  accept that  has a
       basis  in fact  that  contains all  elements  of  the
       offenses  charged  which  is a  requirement  for  the
       court  to accept your  plea of  guilty.   Among those
       elements, those of knowledge and intent.

Flores  then moved  to  sever his  trial  from that  of  the

appellants.  Finding that it would be impossible to mount an

adequate defense if Flores testified in favor of Alvarez and

Matos, the district court  granted both the motion to  sever

Flores'  trial  and  Flores'   request  to  be  tried  after

appellants.

       At  trial,  Matos called  Flores  as  a  witness  who

offered essentially the same testimony as given to the judge

during his  attempted plea.  During  examination by Alvarez,

Flores was permitted to testify that it was a crime to bring

cocaine  into the United States, but he was not permitted to

testify as to the  punishment that could be imposed  for his

crime or as  to his  aborted plea attempt.   The jury  found

Matos and Alvarez guilty on all charges.

                            -9-
                             9

       One  week  later,  Flores   again  came  before   the

district  court to offer his  guilty plea, but  this time he

admitted  that  he knew  cocaine  was  concealed within  the

picture frames.  The court accepted his plea.

II.    Alvarez's Conviction
                           

       Appellant  Alvarez  attacks  his conviction  on three

fronts.    First,  Alvarez  alleges  that  his  defense  was

prejudiced because the district  court erroneously failed to

accept defendant Flores'  guilty plea prior to the  trial of

Alvarez  and Matos.    Alvarez claims  the  judge relied  on

"perceived technical deficiencies" with Flores' plea, rather

than  crediting   the  weight  of   Flores'  testimony  that

indicated he  accepted full  responsibility  for the  crime.

This error, Alvarez argues,  prejudiced his defense  because

he  was deprived of  the opportunity  to put  Flores' guilty

plea before the jury  as persuasive evidence of Mr.  Flores'

credibility and sincerity.  

       We  are  unpersuaded  by  appellant's  argument.    A

criminal  defendant has  no  constitutional right  to  plead

guilty.   North  Carolina v.  Alford, 400  U.S. 25,  38 n.11
                                    

(1970)   (a   trial   judge    need   not   "accept    every

                            -10-
                             10

constitutionally   valid  guilty   plea  merely   because  a

defendant wishes so  to plead").   Nor does Rule  11 of  the

Federal  Rules of  Criminal Procedure  create such  a right.

United States  v. Bednarski, 445 F.2d 364,  365-66 (1st Cir.
                           

1971).    Here, the  district  court  conducted a  prolonged

hearing  to determine  the sufficiency  of Flores'  plea and

carefully  considered his  testimony.   While  Alvarez might

reach  a  different  conclusion  than the  judge  as  to the

factual sufficiency  of Flores'  attempted plea, we  find no

error in district court's determination.  

       Second,  Alvarez  alleges  that  the  district  court

violated both the  Compulsory Process and the  Confrontation

Clauses of  the Sixth  Amendment by improperly  limiting the

scope  of  Flores'  testimony  and,  thereby,  depriving the

defendants of  forceful evidence  of  Flores' sincerity  and

credibility.   On  direct examination,  Matos  asked Flores,

"You  have testified  under  oath  regarding the  exceptance

[sic]  of  a  criminal  offense.    Are  you  aware  of  the

punishment that could be imposed for this crime?"

       The   district   court  sustained   the  government's

objection  to the  question, reasoning  that Flores  had not

actually  pleaded guilty and that  he might or  might not be

found guilty at a later  trial.  Moreover, Flores' testimony

                            -11-
                             11

would not necessarily be  admissible against him in  his own

trial unless he  chose to testify  in his own defense.   The

judge  did, however,  allow Matos  to ask  Flores if  he had

previously asserted the appellants' innocence.  

       Alvarez  then  conducted  what he  termed  a  "cross-

examination" of Flores -- a characterization rejected by the

trial court.   The government argued that even though Flores

was not a joint witness of the appellants, cross-examination

was  unavailable because  Flores was  clearly  testifying in

Alvarez's favor.  Though  we are inclined to agree  with the

trial  court, we need not decide the issue because Alvarez's

Sixth  Amendment  objection  fails  regardless  of  how  the

examination  is  characterized.    Flores  was permitted  to

testify on "cross-examination"  that he knew it  was a crime

to  bring cocaine  into the  United States  and that  he had

"wanted to talk about [his story] for some time."

        The  Confrontation  Clause  of  the Sixth  Amendment

provides that  "[i]n all criminal prosecutions,  the accused

shall  enjoy the  right  . .  .  to be  confronted  with the

witnesses  against  him."    Cross-examination,  the primary

interest  secured  by  the  Confrontation  Clause,  is  "the

principal means by which the believability of a witness  and

the  truth  of  his  testimony are  tested."    Kentucky  v.
                                                            

                            -12-
                             12

Stincer, 482 U.S. 730, 736 (1987)  (quoting Davis v. Alaska,
                                                           

415  U.S.  308,  316  (1974)).    The  Confrontation  Clause

"mandates  a `minimum  threshold of  inquiry' be  afforded a

defendant  in the  cross-examination of  adverse witnesses,"

Brown  v. Powell,  975 F.2d  1, 5  (1st Cir.  1992) (quoting
                

United States  v.  Jarabek,  726  F.2d 889,  902  (1st  Cir.
                          

1984)), cert. dismissed, 122  L. Ed. 2d 179 (1993),  but the
                       

right  to  cross-examination is,  of  course, not  absolute.

Trial judges  retain broad  discretion to impose  reasonable

limits on the scope  of cross-examination.  Delaware  v. Van
                                                            

Arsdall, 475  U.S. 673, 679 (1986).  On appeal, we review to
       

determine:

       whether  the jury  had  sufficient  other information
       before it, without  the excluded evidence, to make  a
       discriminating appraisal  of the  possible biases and
       motivations of the witnesses.

Brown, 975 F.2d at  5 (quoting United States v.  Tracey, 675
                                                       

F.2d 433, 437 (1st Cir.  1982)).  The issue here  is whether

the  district court  abused its  discretion and  committed a

reversible error when it prevented the jury from learning of

the  exact penalties that Flores would  face if convicted of

cocaine  trafficking.   We conclude  the court  committed no

error.

       Flores was  allowed to  put his  entire story  before

the jury, including important information that supported his

                            -13-
                             13

credibility.   The jury heard Flores  testify that importing

cocaine into the U.S. is a crime.  We are confident that the

jury knew that  a conviction for importing  a large quantity

of cocaine carries  a serious punishment.   Though the  jury

did  not  learn of  the  precise  penalty imposed  for  drug

trafficking or  that Flores  had attempted to  plead guilty,

the  decision  to  exclude  this  evidence  was  within  the

district court's  discretion.    The  judge  could  properly

conclude that  such testimony  might mislead or  confuse the

jury;  particularly where,  as here,  the witness  sought to

testify to the same penalties faced by the defendants.  

       We   note  that  Sixth   Amendment  right  of  cross-

examination  is  directed  at  uncovering  witness bias  and

untruthfulness.   In this  case, however, Alvarez  sought to

use "cross-examination" to bolster the witness' credibility.

Contrary to  appellant's assertion, exposing a witness' bias

to lie  can,  indeed, be  more  important than  exploring  a

witness' motivation  for telling  the truth.    Cf. Fed.  R.
                                                   

Evid. 608 (evidence of truthful character is admissible only

after the character of the witness for truthfulness has been

attacked);  Fed. R.  Evid  801 (prior  consistent statements

generally  admissible only  to rebut  an express  or implied

                            -14-
                             14

charge  of  recent  fabrication  or  improper  influence  or

motivation).

       Alvarez  also   asserts  that   the  district   court

violated  the   Compulsory  Process  Clause  of   the  Sixth

Amendment.    According  to  Alvarez,   the  district  court

interfered   with  his   constitutional  right   to  present

witnesses  in his own defense  when it excluded an important

portion  of  Flores'  testimony  that weighed  in  favor  of

Flores'   credibility.     The  Compulsory   Process  Clause

guarantees every criminal defendant "the right . . . to have

compulsory  process for obtaining witnesses in his favor . .

."    This  fundamental  right, however,  is  not  absolute.

Campbell, 874 F.2d at 851; Chappee v. Vose, 843 F.2d  25, 28
                                          

(1st  Cir. 1988).   The  Supreme Court  has explained,  "The

Sixth  Amendment  does  not  confer  the  right  to  present

testimony   free  from   the  legitimate   demands   of  the

adversarial system . . ."  United States v. Nobles, 422 U.S.
                                                  

225, 241 (1975).  As explained more fully above, we conclude

that  the district  court  acted properly  to limit  Flores'

testimony which might have mislead or confused the jury. 

       Third,  Alvarez  complains that  the  district  court

errored  in denying  his  Rule  29  motion for  judgment  of

                            -15-
                             15

acquittal.3    Alvarez   contends  that  the   evidence  was

insufficient  to prove beyond a reasonable doubt that he was

an active participant in  the scheme to import cocaine.   We

review the  evidence to determine whether the  evidence as a

whole, taken in the light most favorable to the prosecution,

together with  all  reasonable inferences  favorable to  it,

would  allow a  rational fact  finder to  conclude  beyond a

reasonable doubt  that the defendant was  guilty as charged.

United  States v.  Maraj,  947 F.2d  520,  522-23 (1st  Cir.
                        

1991); United States  v. Vargas, 945  F.2d 426, 427-28  (1st
                               

Cir.  1991).   A conviction may  be grounded in  whole or in

part on  circumstantial evidence.   Maraj, 947 F.2d  at 523.
                                         

Moreover,  because   the   jury  is   entrusted   with   the

responsibility for making credibility determinations  and is

empowered  to accept  or  reject, in  whole  or in  part,  a

witness' testimony, we will not weigh witness credibility on

appeal.  Maraj, 947 F.2d at 523; Vargas, 945 F.2d at 427.   
                                       

                    

3 Rule 29 provides in relevant part, 

       The court  on motion  of a  defendant or  of its  own
       motion  shall   order  the   entry  of  judgment   of
       acquittal  of one  or more  offenses charged  in  the
       indictment  or  information  after  the  evidence  on
       either   side   is  closed   if   the   evidence   is
       insufficient to sustain a  conviction of such offense
       or offenses.

Fed. R. Crim. Proc. 29.

                            -16-
                             16

       Guilt for  aiding and  abetting  attaches only  where

"the   defendant  associated   himself  with   the  venture,

participated in it as in something he wished to bring about,

and  sought  by his  actions to  make  it succeed."   United
                                                            

States  v. Rodriguez  Cortes, 949  F.2d 532,  539 (1st  Cir.
                            

1991).  Neither mere association with the principal nor mere

presence  at the scene of  a crime, even  when combined with

knowledge that a crime was to be committed, is sufficient to

establish aiding  and abetting liability.   United States v.
                                                            

Aponte-Suarez, 905 F.2d 483,  491 (1st Cir.) (quoting United
                                                            

States  v. Francomano, 554  F.2d 483, 486  (1st Cir. 1977)),
                     

cert. denied, 111 S. Ct. 531 (1990).   Guided    by    these
            

standards  of  review,  we  are  persuaded   that  Alvarez's

conviction  is supported  by  sufficient evidence  of guilt.

There is  no  dispute  that  Alvarez was  traveling  for  an

extended period of  time with  Matos and Flores  and that  a

very large quantity of cocaine was concealed  in the luggage

carried  by  the  group.    Moreover,  there  is  sufficient

evidence upon which a  reasonable jury could conclude beyond

a reasonable doubt that Alvarez participated in or sought to

assist Flores' scheme to import cocaine into the U.S.

       The  evidence established  that  a  Customs Inspector

noticed the group talking "secretively" at the airport; that

                            -17-
                             17

two of the  bags that  concealed cocaine  carried name  tags

bearing  Alvarez's name; and that Alvarez and his common law

wife  had  no means  of  support  other than  welfare,  food

stamps,  and odd jobs and,  yet, they could  still afford to

fly  to Puerto  Rico, travel  on  a cruise  ship, stay  in a

Venezuelan hotel  for several days, and  purchase new cloths

to  replace those purportedly left  on the cruise  ship.  In

addition, the  government  was  able  to  highlight  certain

inconsistencies  in the  testimony  offered  by  Flores  and

Matos.4    Most  significantly, the  government  produced  a

photograph apparently  taken on the cruise  ship that showed

Matos wearing  a striped dress  that according to  her story

was not purchased until after she disembarked from the  ship
                             

in  Caracas.    Matos  explained  that  she  was  apparently

mistaken about  the items of  clothing she carried  with her

when  she left  the ship.   The  government  also introduced

evidence that the cruise  ship operators searched the cabins

used  by Matos,  Alvarez, and  Flores and  did not  find the

luggage  purportedly left  behind  by the  appellants.   The

witness, however, did not conduct the search himself and had

no knowledge of how the search was conducted.

                    

4 Alvarez did not testify at trial.

                            -18-
                             18

       Though  the   evidence   against   Alvarez   is   not

overwhelming, when it is viewed in a light most favorable to

the  prosecution it  is sufficient  to support  the verdict.

We, therefore, affirm Alvarez's conviction.

III.   Matos' Conviction
                        

       In addition to  joining in the arguments advanced  by

Alvarez, Matos contends that her conviction must be reversed

because  the government  presented in  its  case-in-chief an

oral statement allegedly made  by Matos which the government

failed to disclose during pre-trial discovery as required by

Fed.  R. Crim. P. Rule 16.  Specifically, Matos challenges a

portion of  the testimony  given  by Officer  Ortiz, a  U.S.

Customs  Inspector who  searched  Matos' luggage.    Officer

Ortiz  testified that during the  search he asked   Matos if

she  had purchased  the picture  on her  trip, to  which she

answered  "yes."   Ortiz's  testimony  was  the only  direct

evidence that the incriminating picture belonged to Matos.  

       The substance of Officer Ortiz's testimony came as  a

surprise to Matos because she had made two prior requests of

the  government -- first by  letter on January  11, 1990 and

second by formal  motion on  January 22, 1990  -- to  comply

with  the  discovery  provisions  of Rule  16,  including  a

                            -19-
                             19

specific request for any "oral statement[s of the defendant]

which the  Government intends  to offer in  evidence at  the

trial."  The government responded by expressly acknowledging

its  obligations  under Rule  16  and  by producing  several

documents.   The  government,  however, made  no mention  of

Matos'  alleged statement at that time or at any time before

the damaging testimony  came before the jury.  During cross-

examination, Officer Ortiz admitted that his prior testimony

at a preliminary  hearing and  before a grand  jury did  not

include any reference to Matos' alleged statement concerning

the picture.

       The  following morning, Matos moved to strike Officer

Ortiz's  testimony and for the court to admonish the jury to

disregard  the testimony.    Matos argued  that  prosecution

records showed that Officer Ortiz had told the government of

Matos'  alleged  statement  in  April  1990,  but  that  the

government failed to produce  the statement despite repeated

requests by  Matos.   The judge  denied  the motion  without

giving an explanation.

       Rule 16  imposes an obligation  on both the  criminal

defendant and the  government to produce or  disclose to the

opposing party  certain relevant  evidence  prior to  trial.

                            -20-
                             20

The  provisions of Rule 16(a)(1)(A) in effect at the time of

trial provided, in relevant part:

       Upon  request of  a defendant  the government
       shall permit  the  defendant to  inspect  and
       copy  .  .  .   the  substance  of  any  oral
       statement  which  the  government intends  to
       offer in  evidence at  the trial made  by the
       defendant whether before  or after arrest  in
       response to interrogation  by any person then
       known  by the  defendant to  be a  government
       agent.  

Fed.  R. Crim.  P. 16(a)(1)(A).   These  mandatory discovery

provisions  are  intended  to  contribute to  the  fair  and

efficient  administration of  criminal justice  by providing

the defendant with sufficient information upon which to base

an intelligent a plea;  by minimizing the undesirable effect

of surprise at trial; and by contributing to the accuracy of

the fact finding  process.   Fed. R. Crim.  P. 16,  advisory
                                                            

committee's  note.  Where a party fails to comply with these
                 

discovery provisions, Rule 16 empowers the district court to

order   the  party  to   comply  with  the   rule,  grant  a

continuance,  exclude the  non-complying evidence,  or enter

other  such relief as it  considers just.   Fed. R. Crim. P.

16(d)(2).  We review a district court's ruling on the effect

of a failure to provide pretrial discovery only for abuse of

discretion.   United  States v. Nickens,  955 F.2d  112, 126
                                       

(1st Cir.), cert.  denied, 113 S. Ct.  108 (1992); Rodriguez
                                                            

                            -21-
                             21

Cortes, 949 F.2d at 546; see Fed. R. Crim. P.  16(d)(2).  To
                            

succeed  in obtaining a reversal on appeal, a defendant must

prove both an  abuse of discretion and  prejudice.  Nickens,
                                                           

955 F.2d at  126; Rodriguez  Cortes, 949  F.2d at  546.   We
                                   

reverse.

       We  believe the  trial  court erred  when  it  denied

Matos'  motion to exclude the alleged statement or to hold a

suppression  hearing without  first making  a finding  as to

whether the  government acted in bad faith and whether Matos

was prejudiced by admission of the  statement.  We generally

defer  to the  judgment of  a district  judge who  is better

suited to  make factual  determinations based on  first hand

observation  of the  evidence.  In  this case,  however, the

judge  failed to  make  even a  threshold  inquiry into  the

circumstances  leading to  nondisclosure  of the  statement.

The court  neither heard evidence nor  made factual findings

concerning the potential prejudice  flowing from a discovery

violation, the relative importance of Ortiz's testimony, and

the existence of prosecutorial bad faith.   See Nickens, 955
                                                       

F.2d at 126.  This was error.

       Moreover,  this  error  prejudiced  appellant  Matos.

The alleged Matos statement provided a critical link between

Matos and  the effort to  smuggle the cocaine  laden picture

                            -22-
                             22

frame into Puerto Rico.   To establish guilt for  aiding and

abetting,  "the  government  must prove  that  the defendant

associated himself  with the venture, participated  in it as

in something he  wished to  bring about, and  sought by  his

actions  to make it succeed."  Rodriguez Cortes, 949 F.2d at
                                               

539 (quoting United States v. Garcia-Rosa, 876 F.2d 209, 217
                                         

(1st Cir. 1989), cert.  denied, 493 U.S. 1030 (1990)).   The
                              

statement attributed  to Matos was a  very significant piece

of evidence  that indicated Matos  was a participant  in the

crime,  rather  than  merely  being  an  innocent  bystander

present at the  scene of  a crime.   Similarly, the  alleged

statement  fundamentally sabotaged  Matos' defense  that she

was an unwitting participant in Flores'  cocaine trafficking

venture.    There  is  a  substantial  likelihood  that  the

statement  figured  prominently in  the  jury's decision  to

reject  Flores'   account  of  the  incident,  which  wholly

exculpated appellants.  

       Given   the  central   importance  of   the   alleged

statement,  the  government's  failure  to  disclose  it  as

required by  Rule 16  had additional grave  consequences for

Matos.    First,  Matos   was  deprived  of  any  meaningful

opportunity  to investigate the circumstances of her alleged

statement and to attempt to suppress it.  Significantly, the

                            -23-
                             23

government disclosed during  pretrial discovery a  statement

made  by  Alvarez,  which  Alvarez  successfully suppressed.

Second,  not knowing  of  the alleged  statement, Matos  was

deprived  of  the  opportunity   to  design  an  intelligent

litigation or  plea strategy  that responded to  the alleged

statement.  

       The government  contends that  no prejudice  attached

because "it is doubtful that counsel for appellant would not

anticipate  or  contemplate  that  such  a  statement  might

exist."  Even  if this argument  were not inconsistent  with

the mandatory language of Rule 16, we would flatly reject it

as  being  incompatible with  common  sense  and fundamental

fairness.   The  government  also contends  that the  cross-

examination  of  Officer  Ortiz  effectively  impeached  his

testimony  and essentially  cured  whatever prejudice  might

have existed.  While  we have sometimes considered effective

cross-examination   of   witness  when   weighing  potential

prejudice presented by that witness' testimony, Nickens, 955
                                                       

F.2d at 126; United  States v. Samalot Perez, 767  F.2d 1, 4
                                            

(1st  Cir.  1985), those  cases  involved  the admission  of

cumulative evidence that was regarded as harmless error.  In

this  case,   the  alleged   statement  was  vital   to  the

conviction.

                            -24-
                             24

       Finally, the government argues  that since Matos  did

not  present the trial  judge with any  specific grounds for

suppressing  the  alleged   statement,  the  district  court

correctly denied  Matos' request for a  suppression hearing.

During  a  discussion   with  Matos'   counsel,  the   judge

repeatedly  asked  if  the  defendant  had  any  grounds  to

suppress the  statement.  Counsel responded  that he learned

of  the  statement  only the  day  before,  that  he had  no

information regarding the statement, and when pressed by the

judge,  stated  that  at that  time  he  had  no grounds  to
                                   

suppress  the statement other than the violation of Rule 16.

We are not surprised that Matos was unprepared to articulate

a particular  ground  for suppressing  the  statement  under

these circumstances and in the middle  of a trial.  The  one

possible curative course, suspending the trial and holding a

suppresion hearing, was erroneously rejected by the district

court.  

       The  government is  wholly responsible  for  unfairly

surprising the defendant and should not benefit from its own

violation of Rule 16.

       In summary, we  affirm the conviction of Alvarez  and

reverse and remand for a new trial as to Matos.

                            -25-
                             25
