

                  UNITED STATES COURT OF APPEALS                            UNITED STATES COURT OF APPEALS
                      FOR THE FIRST CIRCUIT                                FOR THE FIRST CIRCUIT

                                             

No. 96-1894

                     RAFAELA CORT S-IRIZARRY,

                      Plaintiff, Appellant,

                                v.

             CORPORACI N INSULAR DE SEGUROS, ET AL.,

                      Defendants, Appellees.

                                             

           APPEAL FROM THE UNITED STATES DISTRICT COURT

                 FOR THE DISTRICT OF PUERTO RICO

         [Hon. Salvador E. Casellas, U.S. District Judge]                                                                  

                                             

                              Before

                     Torruella, Chief Judge,                                                     

                  Coffin, Senior Circuit Judge,                                                        

                    and Selya, Circuit Judge.                                                      

                                             

     David Efron, with  whom Kevin  G. Little was  on brief,  for                                                       
appellant.
     Elisa  M. Figueroa  B ez, with  whom  Law Offices  of Sigrid                                                                           
Lopez Gonzalez was on brief, for appellees.                        

                                             

                          April 16, 1997
                                             

          SELYA,  Circuit  Judge.    Plaintiff-appellant  Rafaela                    SELYA,  Circuit  Judge.                                          

Cort s-Irizarry  (Cort s), suing  on behalf  of her  minor child,

Rafael  Jos  Mu iz  Cort s (Jos ),  challenges an  order granting

summary judgment to  Corporaci n Insular de Seguros (CIS) and its

insured, Juan Ram n Gonz lez Aristud (Dr. Gonz lez), in a medical

malpractice action.  See Irizarry v. CIS, 928 F.  Supp. 141, 147-                                                  

48 (D.P.R. 1996).  We vacate the order and remand for trial.

I.  BACKGROUND          I.  BACKGROUND

          Although the  accepted summary judgment  protocol calls

for  us to cast the facts in  the light most complimentary to the

plaintiff's position, consistent with record support,  see, e.g.,                                                                          

Garside v. Osco  Drug, Inc., 895 F.2d 46, 48  (1st Cir. 1990), we                                     

temper that protocol here to the extent that we set off, as point

and counterpoint,  conflicting evidence where the  clash helps to

illuminate pertinent legal issues.  For simplicity's sake we omit

any further reference to CIS and treat its insured as  if he were

the sole defendant.

          Dr.  Gonz lez,  a  specialist in  obstetrics,  provided

prenatal care to Cort s after she  became pregnant with Jos .  On

December 15, 1979, Cort s  related to Dr. Gonz lez that  her last

menstrual  cycle prior  to  conception began  on  November 2  and

lasted  only two days.   The length of  her immediately preceding

menses was three days,  and her periods typically had  lasted two

or three days  during the  year prior to  her current  pregnancy.

Based  on this  data, Dr.  Gonz lez calculated  Cort s' estimated

delivery date (EDD) to be  August 9, 1980.  He delivered  Jos  by

                                2

cesarean section on  July 30,  1980.  The  newborn weighed  eight

pounds,  eight and  three-quarter  ounces (two  pounds more  than

Cort s' first child) and exhibited no fetal distress.

          According to the  defendant's computations, Cort s  was

in her  thirty-ninth  week of  pregnancy when  the baby  arrived.

This  calculation forms  the nub  of the  case.   The plaintiff's

theory  is that Dr. Gonz lez misfigured the baby's fetal age and,

consequently, allowed the pregnancy  to continue beyond forty-two

weeks,  thus bringing  into play  a risk  factor known  as "post-

datism" or "post-maturity."   A  post-dated fetus is  at risk  of

oxygen deprivation during its extended stay in the mother's womb,

and brain damage is a predictable result.  While Jos , at  birth,

displayed   no  detectable   symptoms  suggesting   a  post-dated

delivery,  the   circumstances  of  the  delivery  revealed  some

indications  of potential  perinatal difficulties;  for instance,

the cesarean  section took  twenty-one minutes (roughly  twice as

long as  the norm), and,  on one  view of the  proof, a  tracheal

catheter was used to intubate the newborn.1

          Time resolved  these mixed signals.   Jos  showed signs

of neurologic abnormality at three  months and was diagnosed with

                                                  

     1Other contemporaneous indicators were  inscrutable.  On the
one hand, Jos  had a relatively high Apgar score.  An Apgar score
is comprised of five components:  heart rate, respiratory effort,
muscle  tone,  reflex irritability,  and  color.   It  usually is
compiled by the anesthesiologist at one minute after the delivery
and again  at the  five-minute mark.   A  low score  is generally
thought to have predictive value in determining brain damage.  On
the other  hand, testing at  birth revealed  a somewhat  elevated
serum  bilirubin   level  (which  could   indicate  an  incipient
metabolic problem).

                                3

impaired motor  development and hearing loss  at fourteen months.

His condition worsened as the years passed.  As an adolescent, he

was  diagnosed  as   severely  brain   damaged,  epileptic,   and

profoundly deaf.   At that  juncture, Cort s, then  a citizen  of

Florida,  sued Dr.  Gonz lez  in Puerto  Rico's federal  district

court, see 28 U.S.C.   1332(a) (diversity jurisdiction), alleging                    

that the physician's negligence caused her son's infirmities.

          Cort s'  case rests  primarily on  the opinions  of two

experts.  An  obstetrician, Dr. Bernard Nathanson,  opined that a

competent obstetrician, rather than  relying upon a reported two-

day menstrual  period to  calculate a  gravid woman's  EDD, would

have launched a more detailed gynecologic investigation.  Had Dr.

Gonz lez done so,  the witness stated,  he would have  discovered

that Cort s'  actual  EDD was  July 9,  1980, and  he would  have

recognized that  a substantial risk of post-datism arose when her

pregnancy extended past the EDD (a risk which he presumably could

have negated  by performing  the cesarean section  earlier).   In

reaching  these conclusions, Dr.  Nathanson stressed  the unusual

brevity  of the  reported period  (especially as  contrasted with

Cort s' previous menses) and Dr. Gonz lez' failure to confirm the

EDD by  performing various tests  which the  witness stated  were

available in  1979-1980 (e.g., a B-scan  ultrasound examination).

In Dr. Nathanson's opinion, the pregnancy was post-dated, and the

defendant's  failure to  realize  it and  take corrective  action

violated the prevailing standard of care.

          Dr. Nathanson  also  disputed Dr.  Gonz lez'  assertion

                                4

that  he in fact performed a manual pelvic examination at Cort s'

initial   appointment  and   subsequently  measured   her  uterus

throughout  her pregnancy to corroborate the  EDD.  Dr. Nathanson

saw no evidence that  these steps had been taken.   Moreover, Dr.

Gonz lez'  office  record did  not  mention  either the  periodic

uterine measurements  or their results.  Although some of Cort s'

prenatal charts apparently had  been lost,  Dr.  Nathanson stated

that  these data  "are  so  vital that  they  should  be in  [Dr.

Gonz lez'] record in any case had he done them."

          The plaintiff's second expert, Dr.  Allan Hausknecht, a

neurologist,  diagnosed Jos  as  suffering from  Lennox Gasteault

Syndrome (LGS).  This neurological condition is caused roughly

fifty percent of  the time by  perinatal brain damage  (resulting

from  a lack of  sufficient oxygen to  the fetal  brain).  Doctor

Hausknecht  stated  that,  in  his  experience,  this  percentage

increases sharply when, as  in this instance, no evidence  of any

other known cause exists.  Noting that the gradual development of

Jos 's condition  was characteristic of a  post-mature fetus, Dr.

Hausknecht rendered an opinion  that Jos 's brain damage resulted

from the  post-datism which Dr.  Nathanson had identified.   This

opinion was bolstered in some degree by Dr. Nathanson's statement

that, while some  post-dated infants will show immediate signs of

placental senescence, such as  meconium-stained amniotic fluid or

peeling of the skin  (Jos  had neither), many others  will appear

asymptomatic at birth yet manifest the  effects of post-datism at

a later time.

                                5

          To  be   sure,  the  plaintiff's  evidence   was  hotly

contested.  The defendant   claimed that he  had figured the  EDD

accurately  and that many of the tests suggested by Dr. Nathanson

were  unnecessary, or impracticable, or  both.  He also presented

experts  who   offered  an  alternative   theory  of   causation:

intrauterine  cytomegalovirus (CMV)  infection, a  rare condition

which  occurs in  0.2 to  2.2 percent  of all  live births.   The

results  of blood tests performed on Jos  at age fifteen revealed

previous or  latent CMV infection,  but did not  indicate whether

the   infection  had  been  contracted  in  utero.    This  is  a

significant omission  because, while infants who  suffer from CMV

may  be  asymptomatic  at  birth and  thereafter  develop  mental

retardation  or deafness, CMV can  be transmitted in various ways

and affects most individuals during their lifetimes.

II.  THE SUMMARY JUDGMENT STANDARD          II.  THE SUMMARY JUDGMENT STANDARD

          A court  may grant summary judgment  "if the pleadings,

depositions, answers to interrogatories, and  admissions on file,

together  with  the affidavits,  if any,  show  that there  is no

genuine issue as  to any material fact and that  the moving party

is  entitled to a judgment as a matter  of law."  Fed. R. Civ. P.

56(c).  We  have expounded this standard and its particulars in a

symphony  of cases,  see, e.g.,  McCarthy v.  Northwest Airlines,                                                                           

Inc., 56 F.3d 313, 315 (1st Cir. 1995) (collecting cases), and we              

refrain from  rehearsing this  jurisprudential chorus here.   For

our  purposes,  it  suffices   briefly  to  describe  the  rule's

operation.

                                6

          The  objective of  summary judgment  "is to  pierce the

boilerplate  of the  pleadings and  assay the  parties' proof  in

order to determine whether trial is actually required."  Wynne v.                                                                        

Tufts Univ. Sch. of Med., 976 F.2d 791,  794 (1st Cir. 1992).  To                                  

defeat  a motion for  summary judgment, the  nonmoving party must

demonstrate  the existence  of  a trialworthy  issue  as to  some

material  fact.  See Coyne v. Taber  Partners I, 53 F.3d 454, 457                                                         

(1st Cir.  1995).  A fact  is "material" if it  potentially could

affect the  suit's outcome.   See  Garside, 895 F.2d  at 48.   An                                                    

issue  concerning  such  a  fact  is  "genuine"  if  a reasonable

factfinder, examining  the  evidence and  drawing all  reasonable

inferences helpful to the party resisting summary judgment, could

resolve  the  dispute  in  that  party's  favor.    See  National                                                                           

Amusements, Inc. v. Town of Dedham, 43 F.3d  731, 735 (1st Cir.),                                            

cert. denied, 115 S. Ct. 2247 (1995).                      

          Exercising de novo review,  see Coyne, 53 F.3d  at 457,                                                         

we  hold that the record in  this case presents triable issues as

to whether  Dr. Gonz lez violated his  duty of care,  and, if so,

whether his  actions caused  Jos 's injuries.   Consequently, the

district  court   erred  in   granting  the  motion   for  brevis                                                                           

disposition.

III.  ANALYSIS          III.  ANALYSIS

          We  first survey  the junction  where summary  judgment

principles  and  the  standards  governing the  admissibility  of

expert scientific evidence intersect.  We then evaluate the lower

court's ruling.

                                7

                                A.                                          A.                                            

          The  defendant  asserts on  appeal  that  the entry  of

judgment should  be affirmed because  the district court  had the

power  to exclude  the  plaintiff's expert  evidence pursuant  to

Daubert  v.  Merrell  Dow  Pharmaceuticals, Inc.,  509  U.S.  579                                                          

(1993),  and that,  without such  evidence, the plaintiff  has no

case.  Cort s parries this thrust by contending that Daubert does                                                                      

not  apply at  the  summary  judgment  stage.    The  truth  lies

somewhere in between.

          The  Daubert  Court  formulated  a regime  for  use  in                                

ascertaining  the  admissibility  of  expert  scientific evidence

under  Fed. R. Evid. 702.2   This regime  contemplates that trial

judges  will perform a gatekeeping function, determining "whether

the  reasoning  or  methodology  underlying   [proffered  expert]

testimony  is  scientifically  valid  and  .  .  .  whether  that

reasoning  or methodology properly can be applied to the facts in

issue."   Daubert,  509  U.S. at  592-93;  see United  States  v.                                                                       

Sepulveda, 15  F.3d 1161, 1183  (1st Cir. 1993)  (discussing this                   

function).

                                                  

     2The rule stipulates:

               If   scientific,  technical,   or  other
          specialized knowledge will  assist the  trier
          of  fact to  understand  the  evidence or  to
          determine   a  fact   in  issue,   a  witness
          qualified as  an expert by  knowledge, skill,
          experience,   training,   or  eduction,   may
          testify thereto in the  form of an opinion or
          otherwise.

Fed. R. Evid. 702.

                                8

          The plaintiff  posits that Daubert is  strictly a time-                                                      

of-trial phenomenon.  She  is wrong.  The Daubert regime can play                                                           

a role during the summary judgment phase of civil litigation.  If

proffered expert testimony fails to cross Daubert's threshold for                                                           

admissibility, a  district court  may exclude that  evidence from

consideration when  passing upon  a motion for  summary judgment.

See Cavallo  v. Star Enter., 100 F.3d 1150, 1159 (4th Cir. 1996),                                     

petition for cert. filed,  65 U.S.L.W. 2399 (U.S. Mar.  19, 1997)                                  

(No. 96-1493); Peitzmeier v. Hennessy  Indus., Inc., 97 F.3d 293,                                                             

297-99  (8th Cir.  1996), petition for  cert. filed,  65 U.S.L.W.                                                             

3539  (U.S. Jan.  29, 1997)  (No. 96-1212);  Claar v.  Burlington                                                                           

N.R.R.,  29 F.3d 499, 502-05 (9th Cir. 1994); Porter v. Whitehall                                                                           

Lab., Inc., 9 F.3d 607, 612, 616-17 (7th Cir. 1993).                    

          The  fact that Daubert  can be used  in connection with                                          

summary judgment motions  does not  mean that it  should be  used

profligately.  A  trial setting  normally will  provide the  best

operating environment for the triage which Daubert demands.  Voir                                                                           

dire  is  an extremely  helpful  device  in evaluating  proffered              

expert testimony, see Sepulveda,  15 F.3d at 1184 n.15,  and this                                         

device is not readily available in the course of summary judgment

proceedings.     Moreover,  given  the  complex  factual  inquiry

required by Daubert, courts  will be hard-pressed in all  but the                             

most clearcut cases to gauge the reliability of expert proof on a

truncated record.   Because the summary judgment process does not

conform well to the discipline that  Daubert imposes, the Daubert                                                                           

regime should be employed only with great care and circumspection

                                9

at the summary judgment stage.

          We  conclude, therefore,  that  at  the junction  where

Daubert  intersects  with summary  judgment practice,  Daubert is                                                                        

accessible, but courts must be cautious   except when defects are

obvious  on the  face of  a proffer    not  to exclude  debatable

scientific  evidence  without  affording  the  proponent  of  the

evidence adequate opportunity to  defend its admissibility.3  See                                                                           

Margaret A. Berger, Procedural Paradigms for Applying the Daubert                                                                           

Test, 78 Minn. L. Rev. 1345, 1379-80, 1381 (1994).              

          Having  rejected  the plaintiff's  broadcast contention

that Daubert can never be used at  the summary judgment stage, we                      

turn  to  the  defendant's  case-specific  argument  that Daubert                                                                           

necessitates  the  exclusion  of  the opinions  advanced  by  the

plaintiff's experts.  This asseveration suffers from a very basic

shortcoming:   the  defendant never  asked the district  court to

exclude this evidence from  consideration, and the district court

made no effort to do  so on its own initiative.   If trial courts

should be slow to  employ Daubert at the summary  judgment stage,                                           

appellate courts should  be even  more hesitant to  head in  that
                                                  

     3Though such an opportunity is most easily afforded at trial
or in  a trial-like  setting, courts have  displayed considerable
ingenuity in devising  ways in  which an adequate  record can  be
developed  so  as  to  permit  Daubert  rulings  to  be  made  in                                                
conjunction with motions for summary  judgment.  See, e.g., Brown                                                                           
v. SEPTA  (In re Paoli R.R.  Yard PCB Litig.), 35  F.3d 717, 736,                                                      
739  (3d Cir. 1994) (discussing use of in limine hearings), cert.                                                                           
denied, 115 S. Ct. 1253 (1995); Claar, 29 F.3d at 502 (discussing                                               
district court's  technique of ordering experts  to submit serial
affidavits  explaining the  reasoning and  methodology underlying
their  conclusions).   We  do  not  in  any  way  disparage  such
practices; we merely  warn that  the game sometimes  will not  be
worth the candle.

                                10

direction where there has been no development of the issue below.

After all, the bifurcated  inquiry into reliability and relevance

which Daubert  requires is best  performed by  trial judges  who,                       

unlike appellate judges, have a broad array of tools which can be

brought to bear on  the evaluation of expert testimony.4   Hence,

we can  envision few, if  any, cases in which  an appellate court

would venture to superimpose  a Daubert ruling on a  cold, poorly                                                 

developed  record when  neither the  parties  nor the  nisi prius

court has had a meaningful opportunity to mull the question.

          This case falls squarely into the maw of these  general

principles.   The  defendant, notwithstanding  the animadversions

that he spouts on  appeal, never asked  in the district court  to

strike or otherwise defenestrate the statements of Drs. Nathanson

and/or Hausknecht.   The district court's  rescript neither cites

Daubert nor  purposes to exclude the expert evidence submitted on                 

the plaintiff's behalf.   And, moreover, the record as  it stands

is wholly inadequate to  permit a reasoned Daubert determination.                                                            

For these reasons, we decline the defendant's odd invitation that

we start from  scratch and  undertake a Daubert  analysis in  the                                                         

                                                  

     4It  is for this reason,  coupled with the  special coign of
vantage which trial  courts enjoy, that we have afforded district
judges  broad   discretion  in  determining   whether  particular
scientific testimony is or is not admissible at trial.  See Hoult                                                                           
v. Hoult, 57  F.3d 1, 5  (1st Cir. 1995);  Sepulveda, 15 F.3d  at                                                              
1183.   In this vein,  we note that  the Supreme Court  soon will
resolve a disagreement  among the circuits as  to the appropriate
standard for reviewing  such decisions.   See  Joiner v.  General                                                                           
Elec.  Co., 78  F.3d  524 (11th  Cir.  1996), cert.  granted,  65                                                                      
U.S.L.W.  3619 (U.S. Mar. 17, 1997) (No. 96-188).  That standard-
of-review question need not concern us today.

                                11

context  of this appeal.5   This means,  of course, that  we must

consider  the  entire  record,  including the  opinions  of  Drs.

Nathanson and Hausknecht, as we ponder the merits of the district

court's dispositive ruling.

                                B.                                          B.                                            

          In this  diversity suit, the substantive  law of Puerto

Rico controls.   See  Erie  R.R. v.  Tompkins,  304 U.S.  64,  78                                                       

(1938); Rolon-Alvarado v. Municipality of San Juan, 1 F.3d 74, 77                                                            

(1st Cir. 1993).   The Puerto  Rico Civil Code  states that  "[a]

person who by an act or omission causes damage to another through

fault  or negligence  shall be  obliged to  repair the  damage so

done."    P.R.  Laws Ann.  tit.  31,    5141  (1991).  Under this

proviso, three elements  comprise a prima  facie case of  medical

malpractice; a plaintiff must establish (1) the  duty owed (i.e.,

the minimum standard of professional knowledge and skill required

in  the   relevant  circumstances),   (2)  an  act   or  omission

transgressing  that  duty,  and  (3) a  sufficient  causal  nexus
                                                  

     5In all events, we  note that the two  grounds urged by  the
defendant   in   support   of   his   exclusionary   request  are
inappropriate.    First, Dr.  Gonz lez  asserts  that his  expert
evidence is more persuasive than the plaintiff's.  His insistence
that this circumstance warrants exclusion of the competing expert
evidence contradicts  fundamental principles of  summary judgment
practice.   See, e.g., Greenburg v. Puerto Rico Maritime Shipping                                                                           
Auth.,  835  F.2d 932,  936 (1st  Cir. 1987).   Daubert  does not                                                                 
reverse these principles.   See Daubert, 509 U.S. at  595-96; see                                                                           
also  Ambrosini v. Labarraque,  101 F.3d  129, 140-41  (D.C. Cir.                                       
1996), petition for cert.  filed,     U.S.L.W.     (U.S.  Apr. 1,                                          
1997) (No. 96-1552).  Second, he claims that the testimony of the
plaintiff's witnesses, if allowed, would  be confusing.  The fact
that particular expert evidence might tend  to confuse or mislead
a  jury can constitute grounds  for exclusion of  the evidence at
trial, see  Fed. R. Evid. 403, but it is not directly relevant to                    
a Daubert analysis.  See Daubert, 509 U.S. at 595-96.                                          

                                12

between the breach and the claimed harm.  See Lama  v. Borras, 16                                                                       

F.3d 473,  478 (1st Cir. 1994); Rolon-Alvarado, 1 F.3d at 77.  On                                                        

whole-record  review,  we conclude  that  the  plaintiff produced

sufficient evidence to establish a genuine factual controversy as

to each element.

          1.   Duty and Breach.   In this  case, the  elements of                    1.   Duty and Breach.                                        

duty and breach are  inextricably intertwined.  Thus,  we address

them in the ensemble.

          Puerto  Rico  holds  health  care  professionals  to  a

national standard of  care.  See Oliveros v. Abreu, 101 P.R. Dec.                                                            

209, 226-27, translated in 1 P.R. Sup.  Ct. Off'l Trans. 293, 313                                    

(1973).  Accordingly,  a health care provider has  "a duty to use

the same degree of expertise as could reasonably be expected of a

typically competent practitioner in the identical specialty under

the  same  or  similar   circumstances,  regardless  of  regional

variations  in  professional acumen  or level  of care."   Rolon-                                                                           

Alvarado, 1 F.3d at 77-78.  Nevertheless, because Puerto Rico law                  

presumes  that physicians exercise  reasonable care,  a plaintiff

bent  on  establishing a  breach of  a  physician's duty  of care

ordinarily  must  adduce expert  testimony  to  limn the  minimum

acceptable standard and confirm the defendant doctor's failure to

meet it.  See id. at 78.                           

          Cort s'  proffer  is  sufficient  to  this  end.    Dr.

Nathanson,  a  specialist  in the  same  field  as  Dr. Gonz lez,

clearly delineated the  standard of care  and identified what  he

believed  to  be Dr.  Gonz lez' departures  from  it.   He stated

                                13

categorically that an "average gynecologist" would not rely on  a

reported  two-day  menstrual period     unusually  short even  if

relatively common  to that particular  individual   and  that the

failure  to perform corroborating  tests then  available violated

"the  prevailing  medical standard."    For  purposes of  summary

judgment, affiants and witnesses need not be precise to the point

of  pedantry.  Thus, we  treat Dr. Nathanson's  references to the

"average gynecologist"  and to "the prevailing  medical standard"

as meaning the  national standard of care.  Cf.  Lama, 16 F.3d at                                                               

479 n.7.

          The district court advanced three principal  grounds in

support of its  conclusion that these issues    duty and breach  

could  be resolved against the  plaintiff at the summary judgment

stage, notwithstanding Dr. Nathanson's  opinion evidence.  All of

these grounds lack persuasive force.

          First,   the  court  observed  that  Cort s'  menstrual

periods  had lasted  "an  average of  two  to three  days,"  and,

accordingly,  "a two-day  period  was not  abnormal or  unusually

short  for  her."   Irizarry,  928  F. Supp.  at  146.   But  Dr.                                      

Nathanson's  testimony supported  the opposite  conclusion; thus,

whether the menses was  abnormal and whether it triggered  a duty

to inquire further became questions of fact not properly resolved

on  summary  judgment.    See,  e.g.,  Greenburg v.  Puerto  Rico                                                                           

Maritime Shipping Auth., 835 F.2d 932, 936 (1st Cir. 1987).                                 

          Second, the court determined that, because Dr. Gonz lez

measured  the  uterus  periodically  throughout   the  pregnancy,

                                14

yielding results consistent with  the EDD on which he  relied, he

had no  reason to  suspect an  earlier date  of conception or  to

order any additional tests.   See Irizarry, 928 F. Supp. at  146.                                                    

While Dr. Gonz lez so testified, the court erred in treating that

testimony as conclusive.  When Dr. Gonz lez'  and Dr. Nathanson's

assertions are juxtaposed, the  net result is a factual  issue as

to  whether  the defendant  made  the measurements,  and,  if so,

whether this procedure satisfied the applicable standard of care.

          Third, the  court damned  Dr. Nathanson's  opinion with

the faintest of  praise, characterizing it  as nothing more  than

one doctor's  assertion that he  would have acted  differently in

identical  circumstances  than  did another,  and,  consequently,

denying  it effect in the summary judgment  calculus.  See id. at                                                                        

147.  We accept the  court's premise that a mere disagreement  in

medical  judgment, without more, does not prove duty or breach in

a  medical malpractice case brought  under Puerto Rico  law.  See                                                                           

Rolon-Alvarado,  1 F.3d  at  78.    But  we  reject  the  court's                        

conclusion; Dr. Nathanson's declarations, read in context, amount

to  a  satisfactory statement  of the  standard  of care  and the

defendant's deviation from it which, if credited by a jury, could

support  a finding  for the  plaintiff on  these elements  of her

cause of action.   And in the absence of a  Daubert determination                                                             

excluding the Nathanson evidence as scientifically untenable, the

trial court was not at liberty on summary judgment to ignore that

evidence merely because it deemed other evidence more credible.

          2.   Causation.  Notwithstanding proof of both duty and                    2.   Causation.                                  

                                15

breach,  a  plaintiff  also  must  offer  competent  evidence  of

causation in a  medical malpractice case.   See Rolon-Alvarado, 1                                                                        

F.3d at 77.  The lower court found the plaintiff's submissions on

this element wanting.   See Irizarry,  928 F. Supp.  at 147.   We                                              

demur.

          A medical  malpractice plaintiff can   and often does  

establish causation through expert testimony.   See Lama, 16 F.3d                                                                  

at  478.   Cort s  took that  route.   Dr.  Nathanson offered  an

opinion to a reasonable degree  of medical certainty that Cort s'

EDD was actually  July 9, not August  9, and that  this one-month

discrepancy had  dire consequences.  If  accepted, this testimony

meant  that Dr.  Gonz lez  did not  perform the  cesarean section

until the forty-third week of a post-dated pregnancy.

          Relatedly,  Dr. Hausknecht diagnosed  Jos  as suffering

from LGS,  which, in the  absence of any  genetic or other  known

explanation, is generally thought to be caused by perinatal brain

damage.  It is undisputed that the adverse effects of post-datism

include oxygen  deprivation, and thus  can lead to  brain damage.

Finding no evidence  of any hereditary  etiology and observing  a

pathology consistent with post-datism, Dr. Hausknecht opined that

Jos 's  cerebral damage  probably was  caused by  the post-datism

which  Dr.  Nathanson identified.    Both  physicians also  noted

likely indications of complications  at birth, and these findings

buttress  the  plaintiff's   theory  of   causation.6     Drawing
                                                  

     6Dr.  Nathanson  dwelled  on  the unusual  duration  of  the
cesarean section and the  apparent use of a tracheal  catheter to
resuscitate the infant at birth.  Dr. Hausknecht noted that there

                                16

reasonable inferences  from this evidence, a  rational jury could

find that Dr.  Gonz lez' negligent reliance upon  a reported two-

day  menstrual period  and  his eschewal  of further  (available)

tests  caused  a  post-dated  pregnancy,  the  effects  of  which

included perinatal  brain damage  which manifested itself  in the

form of LGS.

          Of  course,  the   defendant's  experts  debunked   the

plaintiff's  proof and offered an alternative causal theory   the

presence  of a  CMV infection    which  the district  court found

"more  compelling."   Irizarry, 928  F. Supp.  at 147.   But such                                        

comparisons are invidious at the summary judgment stage.  Even at

trial, a plaintiff in a medical malpractice suit need not prove a

causal  connection with  mathematical accuracy nor  eliminate all

other  possible  causes  of  damage.    See   Cruz  Rodriguez  v.                                                                       

Corporaci n de  Servicios del Centro  M dico, 113 P.R.  Dec. 719,                                                      

744,  translated in  13 P.R.  Sup. Ct.  Off'l Trans.  931, 960-61                             

(1983).  Legal rules  of this sort acquire added  significance on

summary  judgment because Rule  56 "contemplates  an abecedarian,

almost one  dimensional, exercise geared  to determining  whether

the nonmovant's  most favorable evidence and  the most flattering

inferences which can reasonably be drawn therefrom are sufficient

to  create any authentic question  of material fact."  Greenburg,                                                                          

835 F.2d at 936.

          In this  case, the defendant's evidence on the issue of
                                                  

had been an  abnormal bilirubin  level at birth  and expressed  a
belief  that this might  evince a metabolic  problem damaging the
brain.

                                17

causation, as compelling as it might have seemed, did not warrant

the  entry of  summary judgment.   The  plaintiff articulated  an

alternative  theory of  causation  and backed  it up  with expert

testimony  as to  the causal  nexuses between  LGS  and perinatal

damage,  and between perinatal  damage and  post-datism.   At the

same time, she cast doubt on the defendant's theory of causation,

establishing the low incidence  of intrauterine CMV infection and

suggesting  an alternate  origin of  any  CMV detected  in Jos 's

system (related  to a  history of  sexual molestation  at school,

thereby  opening up  the possibility that  any CMV  infection was

sexually  transmitted).    This  evidence sufficed  to  create  a

trialworthy issue vis- -vis the element of causation.  See Coyne,                                                                          

53 F.3d at 460 (explaining that "when the facts support plausible

but  conflicting inferences on a  pivotal issue in  the case, the

judge may  not choose  between those  inferences  at the  summary

judgment stage"); see also United States  v. Kayne, 90 F.3d 7, 12                                                            

(1st  Cir. 1996)  (stating that  disagreements among  experts are

"properly the subject of searching cross-examination"  at trial),

cert. denied, 117 S. Ct. 681 (1997).                      

III.  CONCLUSION          III.  CONCLUSION

          We need go no further.  Scrutinizing the  entire record

in the  light most  congenial to  the plaintiff, rational  jurors

could find all the  elements of medical malpractice.   Though the

plaintiff's  evidence may  appear  thin to  some, it  establishes

factual disagreements  as to  which reasonable minds  may differ.

No  more is exigible.  See Greenburg, 835 F.2d at 936 (explaining                                              

                                18

that the  ground rules associated with  summary judgment practice

"admit of no room for credibility determinations, no room for the

measured  weighing  of conflicting  evidence  such  as the  trial

process entails, no  room for  the judge to  superimpose his  own

ideas  of probability  and likelihood  (no matter  how reasonable

those  ideas  may be)  upon the  carapace  of the  cold record").

Right or  wrong, the plaintiff is entitled to present her case to

a jury.

          The order granting summary  judgment is vacated and the                    The order granting summary  judgment is vacated and the                                                                           

case is remanded for trial.  Costs to appellant.          case is remanded for trial.  Costs to appellant.                                                         

                                19
