In the
United States Court of Appeals
For the Seventh Circuit

No. 01-1081

Dura Automotive Systems of Indiana, Inc.,
  formerly known as Excel Corporation,

Plaintiff-Appellant,

v.

CTS Corporation,

Defendant-Appellee.

Appeal from the United States District Court
for the Northern District of Indiana, South Bend Division.
No. 93 C 119--Robert L. Miller, Jr., Judge.

Argued October 26, 2001--Decided April 4, 2002



  Before Posner, Manion, and Diane P. Wood,
Circuit Judges.

  Posner, Circuit Judge. In 1981 the Main
Street Well Field, part of the water
supply of the city of Elkhart, Indiana,
was discovered to be contaminated by TCE
and other volatile organic compounds that
are used as industrial or household
solvents. Twelve years later the EPA,
having cleaned up the contamination, sued
several entities under the Superfund
statute (Comprehensive Environmental
Response, Compensation, and Liability Act
of 1980, 42 U.S.C. sec.sec. 9601 et
seq.), including Dura Automotive Systems
(actually its predecessor, Excel, but
that’s a detail we can ignore), to
recover the costs of the clean-up. Dura
impleaded CTS Corporation, claiming that
it was responsible for some of the
pollution and should therefore be
required to reimburse a share of Dura’s
clean-up expense. The EPA’s claims were
settled or otherwise resolved, leaving
only Dura’s third-party claim against
CTS. At the behest of CTS and on the
authority of Daubert v. Merrell Dow
Pharmaceuticals, Inc., 509 U.S. 579, 592-
93 (1993), the district judge
disqualified Dura’s sole expert witness;
and then, holding that the remaining
evidence was insufficient to create a
genuine issue of material fact, he
granted summary judgment for CTS.

  The groundwater stream beneath CTS’s
plant, a plant that manufactures plastic
by a process that employs volatile
organic compounds, is 3,000 feet west of
the Main Street Well Field and runs
generally south rather than east. In
contrast, Dura’s plant, which also uses
these chemicals, is across the street
from the well field and it was Dura
rather than CTS that was a defendant in
the EPA’s suit. But conceivably some of
the groundwater beneath CTS’s plastics
plant had seeped into the well field back
in the late 1970s or early 1980s,
contributing to the pollution discovered
in 1981. This could only be so, however,
if CTS’s plant was within the well
field’s "capture zone" (in other words,
its catchment basin), the area within
which groundwater, if present, could be
expected to flow to the well field. The
size of the capture zone would depend on
such things as the porosity of the soil
and--a factor particularly emphasized by
the parties--the rate at which the well
field pumps water. The more it pumps, the
larger the capture zone, because the
removal of groundwater beneath the field
causes groundwater to be drawn in by
gravity from other areas.

  To use porosity, pumping, and other data
that bear on the size of the capture zone
to map the zone, hydrogeologists build
mathematical models consisting of systems
of equations that show changes in the
boundaries of the zone as functions of
changes in the causal variables, such as
porosity. These models are used to
predict the future size of capture zones
but they can also be used to estimate the
size of a capture zone in the past if the
requisite historical data on the causal
variables are available, here, for
example, data on pumping rates in the
late 1970s. The parties agree that
without such a model Dura could not prove
its case against CTS. A consulting firm
retained by the EPA in the original suit
had placed CTS’s plant outside the well
field’s capture zone, and if this
placement stood, CTS could not have been
a source of the pollution of the Main
Street Well Field and so Dura would have
no right of reimbursement by CTS.

  Dura designated as its one and only
expert witness Nicholas Valkenburg, a
hydrogeologist who works for a consulting
firm called Geraghty & Miller. At his
deposition, however, Valkenburg admitted
that he was not an expert in mathematical
models of groundwater flow and that the
modeling on which he relied for his
conclusion that CTS’s plastics plant was
indeed within the well field’s capture
zone had been done by other employees of
Geraghty & Miller, using two models,
QuickFlow and SLAEM.

  When CTS moved that Valkenburg be barred
from testifying and that Dura’s third-
party claim be dismissed, Dura responded
with affidavits from four employees or
ex-employees of Geraghty & Miller who had
worked on the Dura project. These
professional groundwater-flow modelers
attested that the models they had used,
QuickFlow and SLAEM, were reliable and
were appropriate for determining the well
field’s capture zone in the late 1970s.
CTS moved to strike the affidavits under
Fed. R. Civ. P. 37(c)(1) on the ground
that Dura’s disclosure of additional
expert witnesses, required by Rule
26(a)(2), was untimely, since the
deadline for filing expert reports had
expired six months previously. The
district judge granted the motion to
strike, and holding that without the
affidavits there was insufficient
evidence of the reliability of the
models, ruled that Valkenburg could not
testify--and without Valkenburg’s
testimony, Dura had no case. So the judge
granted summary judgment for CTS.

  If the affidavits were properly struck,
Valkenburg’s testimony indeed lacked an
adequate foundation. For while there is a
smattering of other evidence about the
models (for example, that they are widely
used), it does not establish their
appropriateness for mapping the well
field’s capture zone 20-odd years ago.
Dura argues, however, that even if
properly struck as untimely expert-
witness reports, so that Dura would not
be able to call the authors as expert
witnesses at trial, the affidavits
remained usable as evidence that the
QuickFlow and SLAEM models were indeed
suitable for the purpose to which
Valkenburg sought to put them. This is
true to the extent that the affidavits
merely attest to facts or opinions on
which Valkenburg would be permitted to
rely, such facts as that SLAEM had been
peer- reviewed. But to the extent that
the affidavits contain evidence that
would have to be presented at trial by an
expert witness or witnesses other than
Valkenburg in order for Dura to withstand
a motion for judgment as a matter of law,
Dura’s failure to have made timely
disclosure of their expert opinions
invited application of Rule 37(c)(1) to
bar the authors of the affidavits, or any
other expert for that matter, from
testifying along with Valkenburg.
NutraSweet Co. v. X-L Engineering Co.,
227 F.3d 776, 785-86 (7th Cir. 2000);
Salgado by Salgado v. General Motors
Corp., 150 F.3d 735, 741 n. 6 (7th Cir.
1998); Lohnes v. Level 3 Communications,
Inc., 272 F.3d 49, 60-61 (1st Cir. 2001).

  We must decide whether the district
judge was reasonable in regarding the
affidavits as experts’ reports that Dura
had failed to disclose to CTS in a timely
fashion rather than merely as
attestations that show that Valkenburg
was competent to report the results of
the modeling exercises undertaken by
other employees of the consulting firm.
As the form in which we have stated the
question makes clear, we must give the
benefit of the doubt to the district
judge. General Electric Corp. v. Joiner,
522 U.S. 136, 141-43 (1997); NutraSweet
Co. v. X-L Engineering Co., supra, 227
F.3d at 786; Yeti by Molly, Ltd. v.
Deckers Outdoor Corp., 259 F.3d 1101,
1106 (9th Cir. 2001).

  An expert witness is permitted to use
assistants in formulating his expert
opinion, and normally they need not
themselves testify. United States v.
Bramlet, 820 F.2d 851, 855-56 (7th Cir.
1987); United States v. Lawson, 653 F.2d
299, 301-02 (7th Cir. 1981). The opposing
party can depose them in order to make
sure they performed their tasks
competently; and the expert witness can
be asked at his deposition whether he
supervised them carefully and whether his
relying on their assistance was standard
practice in his field. If the requisite
assurances are forthcoming, the
assistants’ work need not be introduced
into evidence. Rule 703 of the Federal
Rules of Evidence is explicit that "the
facts or data in the particular case upon
which an expert bases an opinion or
inference may be those perceived by or
made known to the expert at or before the
hearing. If of a type reasonably relied
upon by experts in the particular field
in forming opinions or inferences upon
the subject, the facts or data need not
be admissible in evidence in order for
the opinion or inference to be admitted."

  Analysis becomes more complicated if the
assistants aren’t merely gofers or data
gatherers but exercise professional
judgment that is beyond the expert’s ken.
(They needn’t, of course, be assistants.
We use the term because that seems the
best description of the relation of the
four affiants to Valkenburg, but it would
make no difference if they were
independent experts.) Now it is common in
technical fields for an expert to base an
opinion in part on what a different
expert believes on the basis of expert
knowledge not possessed by the first
expert; and it is apparent from the
wording of Rule 703 that there is no
general requirement that the other expert
testify as well. The Committee Notes to
the 1972 Proposed Rule 703 give the
example of a physician who, though not an
expert in radiology, relies for a
diagnosis on an x-ray. We too do not
"believe that the leader of a clinical
medical team must be qualified as an
expert in every individual discipline
encompassed by the team in order to
testify as to the team’s conclusions."
Walker v. Soo Line R.R., 208 F.3d 581,
589 (7th Cir. 2000); see also United
States v. Smith, 869 F.2d 348, 355 (7th
Cir. 1989); Ferrara & DiMercurio v. St.
Paul Mercury Ins. Co., 240 F.3d 1, 8-9
(1st Cir. 2001). But suppose the
soundness of the underlying expert
judgment is in issue. Suppose a thoracic
surgeon gave expert evidence in a medical
malpractice case that the plaintiff’s
decedent had died because the defendant,
a radiologist, had negligently failed to
diagnose the decedent’s lung cancer until
it was too advanced for surgery. The
surgeon would be competent to testify
that the cancer was too advanced for
surgery, but in offering the additional
and critical judgment that the
radiologist should have discovered the
cancer sooner he would be, at best, just
parroting the opinion of an expert in
radiology competent to testify that the
defendant had x-rayed the decedent
carelessly. The case would be governed by
our decision in In re James Wilson
Associates, 965 F.2d 160, 172-73 (7th
Cir. 1992), where the issue was the state
of repair of a building and "the expert
who had evaluated that state--the
consulting engineer--was the one who
should have testified. The architect [the
expert who did testify] could use what
the engineer told him to offer an opinion
within the architect’s domain of
expertise, but he could not testify for
the purpose of vouching for the truth of
what the engineer had told him--of
becoming in short the engineer’s
spokesman." See also TK-7 Corp. v. Estate
of Barbouti, 993 F.2d 722, 732 (10th Cir.
1993). It is the same here. Valkenburg
could have testified that the well field
was contaminated by volatile organic
compounds and that if CTS’s plastics
plant was within the well field’s capture
zone some of the contamination may have
come from that plant. It does not follow
that he could testify that the plant was
within the well field’s capture zone.

  The Daubert test must be applied with
due regard for the specialization of
modern science. A scientist, however well
credentialed he may be, is not permitted
to be the mouthpiece of a scientist in a
different specialty. That would not be
responsible science. A theoretical
economist, however able, would not be
allowed to testify to the findings of an
econometric study conducted by another
economist if he lacked expertise in
econometrics and the study raised
questions that only an econometrician
could answer. If it were apparent that
the study was not cut and dried, the
author would have to testify; he could
not hide behind the theoretician.

  We must decide whether the district
judge was reasonable in concluding that
this was such a case. The answer lies in
the four affidavits of the Geraghty &
Miller employees who did the modeling
that mapped the capture zone. The
affidavits are much alike, and we can
confine attention to those of James
Rumbaugh, who developed the QuickFlow
model, and of Eric Evans, a current
employee of Geraghty & Miller. Rumbaugh’s
affidavit confirms that QuickFlow is a
system of equations for mapping a capture
zone from data causally related to the
size of the zone. It acknowledges that
modeling groundwater flow (the capture
zone being, remember, the area from which
the groundwater that polluted a given
site could have flowed) "is inherently
not the most precise of scientific tools"
because "one never possesses complete
geotechnical information." (So this is
not like taking an x-ray.) As a result,
"the process of constructing a valid and
useful groundwater model is an iterative
process that requires the exercise of
sound technical judgment in evaluating
all available geotechnical data to
determine what input values should be
used with respect to each parameter
utilized in the model." (In other words,
professional discretion--expertise--is
involved.) Rumbaugh goes on to say that
in his experience "most hydrogeologists
are not experts in modeling"--and we know
that Valkenburg is not; and groundwater
modeling is not the sort of thing that a
lab technician or other subprofessional
does. Rumbaugh therefore "generally
work[s] with other hydrogeologists [such
as Valkenburg] to provide modeling
results upon which they can rely."
Rumbaugh states that he is familiar with
SLAEM and while it is not as
sophisticated as some groundwater models,
it is "entirely adequate and appropriate"
for answering the sort of question posed
by the present case. That of course is an
expert opinion. It is also his expert
judgment (not Valkenburg’s) that "it was
reasonable and appropriate to use
QuickFlow" in the case. He calibrated the
QuickFlow model, that is, compared the
results it generated with observable
results for the current period
(obviously, the accuracy of its map of
the capture zone in the late 1970s cannot
be observed). He attests that the kind of
calibration he did, though visual rather
than quantitative, is "an accepted
practice in the modeling community."

  Evans’s affidavit adds that it is his
"opinion today that the hydrogeologic
data set available to Geraghty & Miller
was adequate for the development of a
groundwater system model that would
provide reliable information regarding
the area encompassed by the Well Field
capture zone under certain conditions"
and specifically that SLAEM "is a valid
tool for determining the extent of the
Well Field ’capture zone’ at various
times in the past," reflecting
"reasonable technical judgments" by
himself, the other affiants, and
Valkenburg. He explains why SLAEM didn’t
have to be recalibrated and attests that
"the use of groundwater models to
simulate historic conditions (’backward-
modeling’) is a valid and a commonly
applied approach" and that "an inherent
assumption" of SLAEM, namely "that
groundwater flow is two-dimensional," is
"valid within the area surrounding the
[Main Street] Well Field." Obviously,
these are expert opinions, not
recitations of cut-and-dried procedures.

  It is apparent from these affidavits
that Valkenburg’s assistants did not
merely collect data for him to massage or
apply concededly appropriate techniques
in a concededly appropriate manner, or
otherwise perform routine procedures, and
that he himself lacks the necessary
expertise to determine whether the
techniques were appropriately chosen and
applied. Remember that there were two
crucial issues--the map of the capture
zone and whether, if CTS’s plant was
within it, how much if any of the
contamination of the well field was due
to the groundwater running beneath that
plant. Valkenburg was not competent to
opine on the first issue, and without an
expert opinion on that issue Dura could
not get to the second and so could not
prevail.

  We are not hydrogeologists, but we can
imagine that the assertion that visual
calibration is an adequate substitute for
exact measurement, or that groundwater
flow is "two dimensional" rather than
three dimensional, would be controversial
in the relevant community of experts.
More important than these conjectures is
Rumbaugh’s reference to the construction
of a groundwater-flow model as an "itera
tive process," a fancy way of describing
tinkering with the original model until
it yields satisfactory results. There is
nothing wrong with such tinkering. But we
must be realistic about expert evidence:
Geraghty & Miller was hired to provide
evidence favorable to Dura; so any margin
of discretion in the construction of the
groundwater-flow model could be expected
to be exploited to Dura’s benefit. That
discretion was exercised not by
Valkenburg but by Rumbaugh and the other
affiants, for it was they who constructed
the model, and the "iterative process" by
which they did so is beyond the scope of
Valkenburg’s expertise. The quotations
that we gave from their affidavits show
the breadth of the expert discretion that
they exercised. Without their testimony
explaining and justifying the discretion
ary choices that they made, his testimony
would have rested on air.

  Had Dura merely wanted to use SLAEM and
QuickFlow to determine the current
capture zone of the Elkhart well field,
we might well have a different case; such
use might be quite routine. Dura wanted
to use these models to determine the
capture zone twenty years ago. The
affidavits make clear that adapting the
models to that use required a host of
discretionary expert judgments for the
affiants, not Valkenburg, to make.

  Dura argues that it could not have
foreseen that the judge would find
Valkenburg unqualified to give expert
testimony in this case and therefore it
should have been forgiven the untimely
filing of additional experts’ reports.
Rule 37(c)(1) states that expert
testimony may not be presented at trial
if the expert’s report was not disclosed
to the other side within the deadline
unless the party was justified in missing
the deadline or the untimeliness of the
disclosure was harmless. As some cases
fail to note, however, see Miksis v.
Howard, 106 F.3d 754, 760 (7th Cir.
1997); Mid-America Tablewares, Inc. v.
Mogi Trading Co., 100 F.3d 1353, 1363
(7th Cir. 1996); Wilson v. Bradlees of
New England, Inc., 250 F.3d 10, 20-21
(1st Cir. 2001), the rule goes on to
authorize the judge, "in lieu of this
sanction . . . [to] impose other
appropriate sanctions," and this
authorization implies, as United States
v. Johnson, 228 F.3d 920, 926 (8th Cir.
2000), rightly holds, that a judge’s
failure to impose a lighter sanction
might be an abuse of discretion even if
the party could not show that missing the
deadline was justified or harmless. Cf.
Sherrod v. Lingle, 223 F.3d 605, 612-13
(7th Cir. 2000). But this is not such a
case. Not only was there no justification
for not disclosing to CTS the opinions of
the other experts--for Dura should have
known that Valkenburg’s expertise did not
extend to scientific issues at once
crucial to the prima facie case and
likely to be contested. In addition, the
suit was in its seventh year when the
judge acted; to have reopened discovery
to give CTS its crack at the additional
experts would have extended the
litigation, and burdened CTS,
unreasonably. Dura is a substantial firm
rather than a hapless individual. Its
reticence about disclosing the other
experts may have been strategic. At all
events, in the circumstances the district
judge could refuse to exercise lenity
without being thought to have acted
unreasonably.

Affirmed.



 DIANE P. WOOD, Circuit Judge, dissenting.
This case is about whether CTS must help
Excel pay for some of the costs of
cleaning up the Main Street Well Field.
(I prefer to use the name "Excel" for the
plaintiff, following the practice of the
district court and both parties; this is
the same company that the majority calls
"Dura.") As the majority opinion
explains, that ultimate question turns
largely on a highly technical
determination about the size of the
Field’s capture zone in the late 1970’s
and early 1980’s. Hydrogeologists working
for the Environmental Protection Agency
(EPA) decided, based on their computer
models and analysis, that CTS’s main
factory and plastics plant (the most
polluted properties in the entire area)
lay outside the crucial capture zone, and
thus that CTS need not contribute to the
cleanup costs. Excel’s expert, Nicholas
Valkenburg, challenges that
interpretation of the data. His own
research places much of the CTS property
within the capture zone and identifies
CTS as a major source of the Field’s
pollution.

  A number of factors account for the
difference between the EPA’s and
Valkenburg’s conclusions about the shape
and size of the capture zone. First,
based on records from the Elkhart water
works office, Valkenburg instructed his
computer modelers, who inputted the data
used to draw the capture zone and then
calibrated the models, to increase the
assumed Field pumping rate to 6 million
gallons per day (MGD) from the 5 MGD
figure that the EPA used. Second,
Valkenburg consulted pond level readings
made by the U.S. Geological Survey and
his own employees over a two-decade span
and lowered the pond recharge rate from 5
MGD to 4 MGD. Third, Valkenburg adjusted
the hydraulic convectivity rates used in
the model. The USGS had determined that
in different parts of the Field the
convectivity rate ranged from 80 to 400
feet per day, but for estimation purposes
the EPA used a rate of 200 feet per day
for the entire model. Valkenburg asked
his modelers to divide the region into
zones based on available data to
construct a more sophisticated model.

  It is clear from reading CTS’s brief
that its principal objection to
Valkenburg’s research was to these
adjustments--or, as CTS says more
pejoratively, to his manipulation of
these variables based on what CTS
considers to be inadequate scientific
foundation. Much of CTS’s four-day
deposition of Valkenburg was devoted to
the technical basis for his adjustments
and estimates. Had a trier of fact in
this case listened to both Valkenburg and
the CTS experts and then determined that
the data utilized by CTS more accurately
represented the characteristics of the
Field circa 1980, I would probably have
little quarrel with such a finding. But
we are not faced with such a challenge
today. Indeed, we are not even evaluating
Valkenburg’s decision to adjust the three
variables I have mentioned. Instead, the
district court’s ruling and the
majority’s opinion focus on a fourth
difference between the EPA and Valkenburg
studies: the computer program used by the
computer modelers to represent the
capture zone. The EPA used two computer
programs called GWPATH and FEMSEEP, which
apparently were not available to the
general public. CTS argues that is best
to rely on a "three-dimensional" modeling
program called MODFLOW, while Excel used
the "two-dimensional" programs QuickFlow
and SLAEM. Both the district court and
the majority believe that Excel’s
evidence is fatally flawed because
Valkenburg, who while an expert in
hydrogeology knows little about the
technical aspects of hydrogeological
computer modeling, played almost no role
in selecting QuickFlow and SLAEM instead
of MODFLOW or some other program.
Instead, he left that task to four
computer modelers employed by Geraghty &
Miller. This specific decision is what
then prompted the inquiry in this case
and the district court’s ruling that
Excel had failed to comply with the
dictates of Daubert v. Merrell Dow
Pharm., Inc., 509 U.S. 579 (1993).

  Since Daubert was decided, the Supreme
Court has addressed its scope on a number
of occasions. It confirmed in General
Electric Co. v. Joiner, 522 U.S. 136, 141
(1997), that the abuse of discretion
standard applies to appellate review of
decisions applying the Daubert framework.
In Kumho Tire Co. v. Carmichael, 526 U.S.
137, 147 (1999), it held that the Daubert
approach applies to all expert testimony,
not simply to scientific evidence. And
recently, in Weisgram v. Marley Co., 528
U.S. 440, 457 (2000), the Court held that
a court of appeals has the authority to
direct entry of judgment as a matter of
law if it concludes that Daubert requires
the exclusion of proffered expert
evidence and the remaining evidence is
insufficient to support a verdict.
Moreover, Daubert’s approach has been
codified in the Federal Rules of
Evidence, in the form of the revised
version of Rule 702 that took effect on
December 1, 2000. The net result of all
of this is a now well-recognized
approach. First, we ensure that the
district court took all of the steps that
a correct application of the Daubert
framework (or, where it applies, amended
Rule 702) requires. That is a legal
inquiry, for which de novo review is
proper. See, e.g., United States v. Hall,
93 F.3d 1337, 1341-42 (7th Cir. 1996).
Beyond that, Joiner makes clear that our
review of particular applications of
Daubert is under the deferential abuse of
discretion standard. Dhillon v. Crown
Controls Corp., 269 F.3d 865, 869 (7th
Cir. 2001).

  It is useful at this point to review
what ought to happen under the Daubert
framework, because in my opinion the flaw
in both the trial judge and the
majority’s analysis comes from a failure
to follow this framework. A trial judge
faced with proffered expert testimony
must initially determine whether the
proposed expert would be testifying about
scientific (or other expert) knowledge
that would assist the trier of fact.
Here, the proffered testimony is easily
characterized as scientific, so I will
limit my discussion to that area.
Determining whether evidence is
scientific "entails a preliminary
assessment of whether the reasoning or
methodology underlying the testimony is
scientifically valid and of whether that
reasoning or methodology properly can be
applied to the facts in issue." 509 U.S.
at 592-93. To make this assessment, the
court must investigate questions such as
whether the expert’s methodology can be
and has been tested, whether it has been
subject to peer review or publication,
what is its known or potential rate of
error, and how generally accepted it is
in the relevant scientific community. Id.
at 593-94.

  The majority has jettisoned this
established framework in its acceptance
of CTS’s criticisms of the computer
programs Valkenburg used. Under the
framework, CTS should have challenged
these programs through the use of its own
experts. Presumably the CTS experts would
have argued that QuickFlow and SLAEM are
unreliable for backwards modeling (that
is, predicting past conditions instead of
projecting future conditions) or that a
hydrogeologist would not reasonably rely
on the results yielded from such a model.
In response, Excel, as the party
supporting Valkenburg’s methodology,
would have been able to introduce
additional expert testimony or written
materials, since hearsay is admissible at
a Daubert hearing and the rules of
evidence do not apply. Daubert, 509 U.S.
at 593 n.10.

  No such Daubert hearing occurred in this
case. CTS has offered no testimony from
any experts even to hint that QuickFlow
and SLAEM are scientifically
questionable. In contrast, as I discuss
below, Excel offered considerable support
for the proposition that they are widely
accepted in the relevant expert community
for substantive (that is, non-litigation)
work. Moreover, the district court never
convened a hearing on the issue; instead,
it simply struck the supporting
affidavits proffered by the computer
modelers themselves. At this point, the
majority criticizes Excel for not naming
the modelers earlier, but it is not at
all obvious that this should have been
done. No one else had delved that deeply
into the background programs and
materials from which the hydrogeologists
were forming their opinions; to the
contrary, both the EPA and the other
principal defendant also disclosed only a
single expert hydrogeologist as a
witness. While it is possible that these
individuals are expert computer modelers,
that seems unlikely.

  I am deeply concerned that the
majority’s approach will have the effect
of transforming--in a manner
uncontemplated by and unauthorized by
Rule 702--the way in which litigants
approach the use of expert witnesses in
all kinds of cases. All experts, and all
people for that matter, rely on the
expertise of others. Cautious parties
will feel compelled to engage in
something like an infinite regression of
the naming of experts. Expert 1 may have
relied on something prepared using the
expertise of Expert 2, who in turn relied
on the expertise of Expert 3, and on out
until we reach Expert N. There is no
reason to assume that Experts 2, 3, and
others are "hiding behind" Expert 1, if
the information they produce is commonly
relied upon by people in the field of
Expert 1. Indeed, Rule 702 permits
exactly this kind of reliance, as I
explain later. Thus, it makes no
difference to my analysis whether we
consider the computer modelers to be
"mere" technicians or experts in their
own right. The critical question is
instead whether CTS ever introduced any
evidence tending to show that a
hydrogeologist would not commonly rely on
their choice of a computer model.

  Recall that here Valkenburg ordered his
modelers to increase the pumping rate
used in the models based on a review of
the Elkhart city water records. CTS also
argued below that this evidence was
suspect because Valkenburg himself did
not inspect the water records, leaving
that chore to his assistants, and because
Valkenburg testified that he did not know
how Elkhart’s water records were kept.
While the majority might decide that
these tasks lack discretion and do not
require testimony at trial, another
district court might take a different
view of the matter. The radiologist, the
computer modeler, the data collector, the
Water Department recordkeeper, even the
lab technician who selects a test tube
that is not of the highest quality on the
market all exercise some measure of
discretion that could conceivably
influence an expert’s end product. And
since the expert can never supplement an
expert report in any way under the
majority’s approach, the only responsible
course would be to disclose all of these
individuals as potential expert witnesses
and have each submit a comprehensive Rule
26(b)(2)(B) expert report, fueling ever
more time-consuming and expensive
litigation.

  Nothing in Daubert, any of the later
Supreme Court decisions, or amended Rule
702 requires any such thing; the Daubert
approach is designed only to ensure that
an expert’s methodology is reliable and
accepted rather than quack science. But
that one central question was never
explored here, because as I have already
mentioned the district court never
conducted a Daubert hearing or heard a
single CTS expert opine that Valkenburg
had made unreliable assumptions or had
utilized an unaccepted computer program
in reaching his conclusions about the
Field capture zone and the migration of
chemicals from the CTS plastics plant.
This was a failure of procedure, not a
discretionary decision about the way to
apply the Daubert factors in a particular
situation. I thus regard it as the kind
of thing this court should review de
novo. Cummins v. Lyle Indus., 93 F.3d
362, 367 (7th Cir. 1996). Because the
district court and the majority’s
approach drastically modifies the Daubert
analytical framework, I cannot accept its
conclusions.

  Turning briefly to the details of the
Daubert analysis, let me suppose for a
moment that we should disregard the
affidavits of the four computer modelers
who were prepared to testify about the
general acceptance of the programs on
which Valkenburg relied. Even without
those affidavits, the only evidence in
the record is that SLAEM is a generally
accepted computer program in the modeling
community. The program has been used by
the lead environmental agencies of the
United States, the Netherlands, and
Minnesota. It has been published and has
sold well in commercial markets.
Valkenburg unequivocally testified that
SLAEM is widely used by hydrogeologists
outside the litigation context, a major
indicator of reliability. Daubert, 509
U.S. at 593. (Most lawyers widely use
computer research programs like LEXIS
and WestLaw, and they would be competent
to testify about their general
acceptance, even if they do not know how
the programs were written.) Valkenburg
also noted that his model can be
validated and calibrated by visually
comparing its projections to actual
current water levels, which could help
determine an error rate. Id. at 594.

  While CTS baldly asserts that
Valkenburg’s methodology is unreliable
and the majority "imagines" that
hydrogeologists might find something
controversial or suspect about visual
calibration or two-dimensional modeling,
CTS has presented no hydrogeologist or
other scientist to attest to this fact.
Indeed, the only information we have
suggests exactly the opposite: Excel
contends that CTS’s own environmental
consulting experts used visual
calibration in constructing their models.
Even under abuse of discretion review,
when CTS has offered nothing to challenge
any of the support offered by Excel, I
see no possible way to hold that either
SLAEM or QuickFlow are inherently
unreliable or that an expert
hydrogeologist would for some other
reason not rely on them.

  As a theoretical matter, I have no
problem with the majority’s proposition
that a thoracic surgeon in a medical
malpractice suit cannot testify that a
radiologist was negligent for failing to
diagnose lung cancer at an earlier time,
or that a theoretical economist may not
serve as a "mouthpiece" for an
econometrician. But the real question is
whether those analogies fit the situation
of a hydrogeologist’s reliance on a
computer modeler’s choice of a program. I
think not. The dispute here is far more
like the x-ray example from the Advisory
Committee Notes to the 1972 Proposed
Rules, which permits a physician to rely
upon x-rays in formulating her
diagnosis,/1 or, even more
appropriately, like a case in which the
opposing party objected to a physician’s
testimony on the ground that the
radiologist who took the x-rays relied on
an x-ray machine that was old,
antiquated, or in some other way
inadequate under modern day standards.
The only objection ever voiced even by
CTS’s counsel (whose expertise in these
matters is certainly unproven) is that
QuickFlow and SLAEM are inferior two-
dimensional programs that require visual
calibration and therefore give inaccurate
and scientifically unsound results.
Daubert and the Federal Rules of Evidence
anticipate only a basic inquiry into
whether an expert physician would
reasonably rely on a radiologist to do
her job and use adequate and up-to-date
technology and whether an expert
hydrogeologist such as Valkenburg would
reasonably rely on his computer modelers
to select an adequate and up-to-date
computer model to crunch the data
necessary for him to interpret his
results. The record shows that he would.
  This does not mean that if a physician
really did rely on a radiologist who used
an inferior x-ray machine the results
could go unchallenged; it means only that
such potential flaws go to the weight,
not to the admissibility, of the
evidence. The party’s opponent would have
an opportunity to introduce an expert
radiologist in rebuttal under Rule
26(a)(2)(C) who could assert that,
although a physician would normally have
every right to rely on a radiologist’s
work, in this specific case that reliance
was unjustified. But CTS has introduced
no such expert here. The only evidence in
the record is that an expert
hydrogeologist would reasonably rely on
computer modelers to select appropriate
computer models and plug in the data the
hydrogeologist provides to produce
accurate capture zones.

  In the end, even CTS’s argument makes it
clear that the dispute here is about
Valkenburg’s decisions as a
hydrogeologist, not about the computer
program he was using. As CTS repeatedly
noted in its motion before the district
court, Valkenburg acknowledged in his
deposition that when he had earlier
instructed his computer modelers to run
QuickFlow and SLAEM using the same
variables that CTS and the EPA had used,
the CTS plants were not located within
the capture zone. This indicates that the
computer program used has little or
nothing to do with the real dispute in
this case: the correctness of
Valkenburg’s expert opinion that the
pumping, pond recharge, and hydraulic
convectivity rates were different than
the EPA had thought. That dispute is all
about the variables and data that Valken
burg, not the computer modelers, decided
to use for the program. Assuming that
Valkenburg used reliable and generally
accepted methods in determining those
variables (another issue never reached by
the district court) these questions
should be resolved as a factual matter at
trial. The fact that the selection of a
computer program, whether a "two-
dimensional" or "three-dimensional"
model, seems largely irrelevant to the
final analysis also likely explains why
Excel considered it unnecessary to
disclose any of its computer modelers as
expert witnesses under Rule 26(a)(2)(A),
as opposed to the majority’s speculation
about strategic motivations. CTS was well
aware of the existence of each of Excel’s
four modelers since their work and
computer models were turned over in
response to discovery requests in August
1996. One of the modelers, Eric Evans,
has even been deposed by CTS. It is quite
hard to see what Excel could possibly
have gained strategically through an
attempt to hide them.

  Finally, let us suppose that there is
now some controversy regarding the use of
QuickFlow and SLAEM for modeling in this
case. Everyone agrees that Valkenburg
cannot testify about the differences
between these programs and others that
might have been used because he is not an
expert modeler, and so additional
testimony is required to rebut this
challenge. The district court found that
because Excel had failed to disclose the
four computer modelers earlier (as
experts; at least two of the modelers
were disclosed as fact witnesses), it was
compelled to strike their testimony by
Fed. R. Civ. P. 37(c)(1). Rule 37 is
designed to prevent a party from
springing new expert testimony on an
opponent at the last minute. The remedy
of striking testimony is admittedly a
drastic one, and some circuits have found
discretion to relax it, Newman v. GHS
Osteopathic, Inc., 60 F.3d 153, 156 (3d
Cir. 1995); Orjias v. Stevenson, 31 F.3d
995, 1005 (10th Cir. 1994). We, however,
have held that exclusion is automatic
unless the sanctioned party proves that
its violation was either justified or
harmless. NutraSweet Co. v. X-L Eng’g
Co., 227 F.3d 776, 786 (7th Cir. 2000).

  I believe the failure to disclose was
both justified and harmless. First, since
the changes in variables, rather than the
specific modeling program used, appear to
account for most if not all of the change
in the size of the capture zone, Excel
was justified in producing an expert who
could respond to these criticisms without
worrying about the more technical aspects
of its experts’ work. Furthermore, the
only harm cited by the majority opinion
is the seven years that have elapsed
since this case began. But that is a
misleading time frame. The case was
stayed for nearly three years while the
United States and most of the other
parties negotiated a settlement. Then the
district court took over thirteen months
to rule on the motion to strike. The case
has been pending before this court for
over a year. Thus, the case was in active
discovery for just a little under two
years, hardly a great span of time in a
complicated environmental cleanup suit.
The only other harm noted by the district
court was that CTS might have to hire
additional computer modelers to testify.
Presumably, though, CTS must already have
some modelers on hand who dispute the
validity of QuickFlow and SLAEM, or else
its attorneys could not credibly raise a
challenge to Valkenburg’s reliance on the
programs. I therefore cannot conclude
that CTS has been harmed. In summary,
even if I am wrong about the need for the
testimony of the computer modelers, I
would find that their affidavits fit
within the exception noted by NutraSweet,
because Excel’s failure to present them
earlier was both justified and harmless
to CTS.

  No one should be under any illusions
about the importance of the difference of
opinion between the majority and myself.
The majority thinks that every party who
wishes to proffer expert testimony has an
obligation under the discovery rules to
name as an expert everyone whose
expertise in any way affects the opinion
of another expert: my example of Experts
1 through N above. In my opinion, Rule
702 expressly permits one expert to rely
on the informed opinion of other experts.
An opposing party who wishes to argue
that the underlying expert’s opinion is
contestable, in the sense that both
Daubert and amended Rule 702 use this
idea, is entitled to produce evidence to
that effect. That should occur during the
Daubert/Rule 702 hearing. At that point,
if the court agrees that it is confronted
with a situation more like the
theoretical economist and the
econometrician than like the doctor and
the x-ray technician, the court should
afford the party proffering the evidence
the opportunity to name Expert 2. That
system respects the fact that in our
complex society, all experts rely in
countless ways on the conclusions of
other experts, and it structures the
process for deciding which of those many
experts must testify at a trial. The
majority’s rule does not; it proceeds
from the unwarranted assumptions that
experts are "hiding behind" the work of
other experts, that there is no
obligation on the resisting party to
introduce so much as a scrap of evidence
to challenge the secondary expert’s work,
and that parties must name everyone from
the hydrogeologist to the weatherman from
Day 1. Although many might have thought
that litigation in areas like
environmental disputes, antitrust, and
intellectual property could not become
more unwieldy and expensive than it
already is, the majority has shown them
to be wrong. Its rule will hamper
governmental plaintiffs (like the EPA in
this very case, which named only a
hydrogeologist) just as much as private
plaintiffs, and defendants just as much
as any plaintiffs. Furthermore, its
approach is inconsistent with amended
Rule 702, with the "just, speedy, and
inexpensive determination of every
action" command of Fed. R. Civ. P. 1, and
with a fair balance of obligations on
both parties.

  I would Reverse the district court’s
judgment, and I respectfully dissent.

FOOTNOTE

/1 The committee’s comments are instructive. It said
"the rule is designed to broaden the basis for
expert opinions beyond that current in many
jurisdictions and to bring the judicial practice
into line with the practice of the experts them-
selves when not in court. Thus a physician in his
own practice bases his diagnosis on information
from numerous sources and of considerable vari-
ety, including statements by patients and rela-
tives, reports and opinions from nurses, techni-
cians and other doctors, hospital records, and X
rays." Advisory Committee Notes to Proposed Rule
703. It is evident that some of the information
that the Committee considered legitimate as a
basis for the expert’s testimony is itself the
product of the expertise of others, such as the
work of other doctors, or the evidence from x-
rays. Yet this was not a reason to forbid the
first expert from testifying. Those who wished to
challenge the testimony were responsible for
impeaching the basis for it with their own coun-
terexpertise.
