United States Court of Appeals
                          FOR THE EIGHTH CIRCUIT
                                    ___________

                                    No. 08-3524
                                    ___________

In re: Baycol Products Litigation     *
__________________________            *
                                      *
David Flesner,                        *
                                      *
            Appellant,                * Appeal from the United States
                                      * District Court for the
      v.                              * District of Minnesota.
                                      *
Bayer AG; Bayer Corporation, a        *
wholly owned subsidiary of Bayer AG; *
SmithKline Beecham Corporation,       *
doing business as                     *
GlaxoSmithKline PLC, doing business *
as GlaxoSmithKline,                   *
                                      *
            Appellees.                *
                                 ___________

                             Submitted: October 22, 2009
                                Filed: March 3, 2010
                                 ___________

Before LOKEN, Chief Judge, HANSEN and MELLOY, Circuit Judges.
                              ___________

MELLOY, Circuit Judge.
       This is a failure-to-warn case involving the prescription drug Baycol, a
cholesterol-reducing medication. The case comes to us after the district court1 granted
Bayer's motion for summary judgment on Flesner's claims for strict liability,
negligence, express and implied warranty, and unjust enrichment. On appeal, our
decision focuses on whether the district court abused its discretion in finding that
Flesner failed to present competent expert testimony on medical causation, requiring
entry of summary judgment. We also address whether the district court abused its
discretion in striking, as untimely, Flesner's supplemental expert report. For the
following reasons, we affirm the judgment of the district court on both issues.

                                           I.

      Cerivastatin, marketed under the brand name Baycol, is a prescription
cholesterol-reducing medication manufactured by Appellees Bayer AG and its
subsidiary Bayer Corporation and marketed by Appellees Bayer and
GlaxoSmithKline. Baycol is a member of a class of drugs called statins. Doctors
routinely prescribe statins to lower the lipid levels of patients diagnosed with high
cholesterol, with the goal of decreasing the risk of heart disease and stroke. In August
2001, Bayer withdrew Baycol from the market after a number of deaths were linked
to Baycol use and reports suggested a link between Baycol and myopathy.2

    After Bayer withdrew Baycol from the market, plaintiffs throughout the country
commenced lawsuits asserting various claims, including strict liability, negligence,

      1
       The Honorable Michael J. Davis, Chief Judge, United States District Court for
the District of Minnesota.
      2
       Myopathy entails a broad range of muscle damage, which can be grouped into
three categories, with increasing levels of severity: myalgia, myositis, and, the most
severe, rhabdomyloysis. See Stedman's Medical Dictionary (24th ed. 1982). Because
any distinction is immaterial to our decision here, we refer broadly to Flesner's alleged
condition as "myopathy."

                                          -2-
breach of express and implied warranty, medical monitoring, and unjust enrichment.
Due to the number of lawsuits initiated, the Judicial Panel on Multidistrict Litigation
consolidated plaintiffs' cases in the District of Minnesota under 28 U.S.C. § 1407. See
In re Baycol Prods. Liab. Litig., 

, 1380 (J.P.M.L. 2001). Among
those plaintiffs is Appellant, David Flesner.

       Flesner, a sixty-seven-year-old California resident, has been treated by his
primary-care physician, Dr. Milan Brandon, since 1969. Flesner first sought treatment
for back and neck pain when Dr. Brandon treated him for an on-the-job injury in
1988. Dr. Brandon prescribed a variety of medications to treat this pain. Flesner also
received chiropractic treatment from Dr. Robert McPherson, beginning in August
2000, when Flesner suffered an injury from being hit by a tree branch and began to
suffer neck and back pain. Dr. Gary Miller later took over chiropractic treatment for
Flesner's back and neck pain.

      Flesner's experience with statins began in November 1999 when Dr. Brandon
prescribed Zocor, and later Provachol, after diagnosing Flesner with high cholesterol.
In February 2001, after weighing the risks and benefits associated with the
medication, Dr. Brandon prescribed Baycol to Flesner. On March 15, 2001, Flesner
complained to Dr. Miller about "general body fatigue and pain, with specific
complaints of severe pain in his lower back, hips, and legs." During the same month,
Flesner requested that Dr. Brandon renew his Baycol prescription. Dr. Brandon
complied.

       Flesner continued to express concern about muscle pain to Dr. Miller though
May 2001. In late May 2001, Flesner complained in a note to Dr. Brandon about pain
in his lower back and groin and dark red blood in his urine. Dr. Brandon informed
Flesner that a kidney stone was the likely cause of these symptoms. Flesner continued
to complain to his doctors about this pain through June and July 2001.



                                         -3-
       In August 2001, after taking Baycol for nearly five months, Flesner
discontinued his use of Baycol after reading in a newspaper article that Bayer had
withdrawn Baycol from the market. Continuing to experience muscle pain and
fatigue, Flesner sent a letter to Dr. Brandon in which he hypothesized that Baycol was
causing his symptoms. On August 13, 2001, Dr. Brandon performed a blood test,
which indicated that Flesner's creatine kinase ("CK")3 levels were slightly above
normal—Flesner's CK level was 234; up to 200 is considered normal. Dr. Brandon
informed Flesner that his elevated CK level was consistent with Flesner's suspicion
that Baycol was the cause of his symptoms, but that "[a]ny pains related to Baycol
should have long passed." Since discontinuing Baycol treatment, Flesner has had four
CK tests, three of which have been outside of the normal range.

       In July 2002, Flesner filed suit in the Southern District of California, alleging
that, due to inadequate warnings, Baycol caused the various symptoms he suffered and
continues to suffer. He asserted five claims under California law: (1) strict liability;
(2) negligence; (3) breach of express warranty; (4) breach of implied warranty; and
(5) unjust enrichment.

       As a part of the consolidated Baycol litigation, Flesner's case was transferred
from the Southern District of California to the District of Minnesota. Bayer
subsequently brought a number of Daubert4 motions to exclude expert testimony. See
generally, In re Baycol Prods. Litig., 

(D. Minn. 2007). As it
pertains to Flesner, the district court barred plaintiffs' experts Dr. Samuel Mayer and
Dr. Stephen Raskin from testifying that Baycol was more toxic than other statins. 

1068. In addition, the district court barred Dr. Mayer from testifying as to



      3
      CK is a chemical released into the bloodstream when muscles die. A rise in
CK level is one indication of the presence of myopathy.
      4
       Daubert v. Merrell Dow Pharm., Inc., 

(1993).

                                          -4-
Baycol's long-term effects. 

Finally, the court barred Dr. Raskin from
testifying as to the sufficiency of the Baycol warning label. 

      Three weeks after the district court's Daubert opinion, seven months after Dr.
Mayer's deposition, and nearly a year after the court-imposed deadline for submission
of case-specific discovery, Flesner submitted a supplemental expert report from Dr.
Mayer. Bayer filed a motion to strike Dr. Mayer's supplemental report as untimely.
The district court granted the motion to strike, finding that Flesner could not show
good cause for the late submission and that Bayer would be prejudiced by the
admission of Dr. Mayer's supplemental report. In the same opinion, the district court
granted Bayer's motion for summary judgment on each of Flesner's claims. Flesner
appeals both of these rulings. We affirm.

                                            II.

       District courts have broad discretion in establishing and enforcing deadlines and
in maintaining compliance with discovery and pretrial orders. See Marmo v. Tyson
Fresh Meats, Inc., 

, 758–59 (8th Cir. 2006). We review a district court's
ruling only for "clear and prejudicial abuse of discretion." Wegener v. Johnson, 

, 690 (8th Cir. 2008). In this case, there is no question that Dr. Mayer's
supplemental report was late—Flesner submitted the report nearly a year after the
court-imposed deadline. The question is whether he was justified in doing so.

      Flesner's only proffered reason for the delay was that Dr. Mayer "reviewed the
records of Mr. Flesner in greater detail." This explanation is insufficient, as there is
nothing in the record to indicate that Dr. Mayer could not have reviewed Flesner's
records in detail at the time of his initial report. See 

("[Plaintiff's] failure
to exercise due diligence with respect to her expert's review of relevant medical
records . . . does not substantially justify her untimely disclosure."). In addition, it is
not unreasonable to conclude that Bayer would be prejudiced by Flesner's late

                                           -5-
submission, given that Bayer had already deposed Dr. Mayer and moved for summary
judgment based on his initial report and deposition. See 

;
accord Trost v. Trek Bicycle Corp., 

, 1008–09 (8th Cir. 1999) (stating
that because defendant had prepared its summary judgment motion, in part, on initial
disclosure of expert-witness testimony, the district court did not abuse its discretion
in excluding plaintiff's untimely disclosed expert). For these reasons, the district court
did not abuse its discretion.

                                           III.

       "We review the district court's grant of summary judgment de novo and may
affirm on any basis supported by the record." Tenge v. Phillips Modern Ag. Co., 

, 906 (8th Cir. 2006). Summary judgment is appropriate when the evidence,
viewed in the light most favorable to the nonmoving party, demonstrates "that there
is no genuine issue as to any material fact and that the movant is entitled to judgment
as a matter of law." Fed. R. Civ. P. 56(c); Henerey v. City of St. Charles, Sch. Dist.,

, 1131 (8th Cir. 1999). "[T]he plain language of Rule 56(c) mandates
the entry of summary judgment, after adequate time for discovery and upon motion,
against a party who fails to make a showing sufficient to establish the existence of an
element essential to that party's case, and on which that party will bear the burden of
proof at trial." Celotex Corp. v. Catrett, 

, 322 (1986). We review for
abuse of discretion the district court's decision to exclude expert testimony for
purposes of determining whether there exists an issue of material fact. Gen. Elec. Co.
v. Joiner, 

, 142–43 (1997); Ahlberg v. Chrysler Corp., 

, 635
(8th Cir. 2007). We first address Flesner's strict liability, negligence, and warranty
claims, and then address Flesner's unjust-enrichment claim.




                                           -6-
                                            A.

        The district court granted summary judgment on Flesner's claims for strict
liability, negligence, and express and implied warranty. In regard to the strict liability
and negligence claims, the district court found that Flesner could not meet his
causation burden because he failed to present an expert capable of testifying with a
reasonable degree of medical probability that Baycol contributed to his injuries. The
court found that Flesner's warranty claims failed because the Baycol labels "warned
of the side effects [Flesner] alleges." On appeal, we limit our analysis to whether
Flesner has met his burden of proving causation on each of these claims. We find that
he has not.

       To succeed in his strict liability and negligence claims, Flesner has the burden
of proving medical causation through the use of a medical expert. Bockrath v. Aldrich
Chem. Co., Inc., 

, 403 (Cal. 1999) ("In cases . . . presenting complicated
and possibly esoteric medical causation issues, the standard of proof ordinarily
required is 'a reasonable medical probability based upon competent expert testimony
that the defendant's conduct contributed to [the] plaintiff's injury.'") (citation omitted).
Causation is also a required element in a claim for breach of express or implied
warranty. Pisano v. Am. Leasing, 

, 80 (Cal. Ct. App. 1983). Under
California law, proof of causation in this context requires that Flesner demonstrate to
a "'reasonable medical probability based upon competent expert testimony that the
defendant's conduct contributed to [his] injury.'" Rutherford v. Owens-Illinois, Inc.,

, 1219 n.11 (Cal. 1997) (citation omitted). Probability is a higher
standard than possibility, requiring Flesner to prove that, "in the absence of other
reasonable causal explanations, it [is] more likely than not that the injury was a result
of [Bayer's] action. This is the outer limit of inference upon which an issue may be
submitted to the jury." Jones v. Ortho Pharm. Corp., 

, 460 (Cal. Ct.
App. 1985). While Flesner points to the testimony of various "generic causation
experts" who are able to testify as to general causation—that is, whether Baycol is
capable of causing myopathy—the issue on appeal is specific causation—whether
                                            -7-
Baycol caused Flesner's alleged injuries. See Whiteley v. Philip Morris Inc., 11 Cal.
Rptr. 3d 807, 863 (Cal. Ct. App. 2004) ("'[P]laintiffs must establish, to a reasonable
medical probability, their illnesses were caused by the toxic exposure. The fact the
chemicals increased the possibility of sickness in the overall population does not
suffice to provide a causal link with plaintiffs' illnesses.'") (citation omitted).

       On this point, Flesner relies on the testimony of Dr. Mayer, his case-specific
expert.5 Specifically, he relies on two reports: (1) Dr. Mayer's generic expert-witness
report, which Dr. Mayer submitted in the consolidated Baycol litigation; and (2) Dr.
Mayer's case-specific expert report. Dr. Mayer's generic report concluded only that
Baycol is capable, as a general matter, of causing myopathy. Because this is not at
issue on appeal, we focus on Dr. Mayer's case-specific expert report in determining
whether the district court abused its discretion in excluding Dr. Mayer's testimony on
causation.6 We find that Dr. Mayer had inadequate factual evidence on which to base
his opinion.

       Dr. Mayer's case-specific expert report fails to provide competent evidence on
specific medical causation, particularly in light of Dr. Mayer's deposition testimony.
Upon reviewing the record, it is apparent that Dr. Mayer's testimony on causation is
devoid of the factual basis necessary to render it sufficient to create a triable issue of
fact. See McGonnell v. Kaiser Gypsum Co., Inc., 

, 29 (Cal. Ct.


      5
       In addition to excluding Dr. Mayer's testimony, the district court found that
Flesner's treating physicians, Drs. Miller and Brandon, could not testify to a
reasonable medical probability on causation. Flesner does not appear to rely on
testimony from Drs. Miller and Brandon on appeal. Rather, Flesner focuses on Dr.
Mayer's testimony. In any event, the record is clear that neither Dr. Miller nor Dr.
Brandon could testify with the requisite degree of certainty that Baycol contributed
to Flesner's alleged injuries.
      6
        Bayer has not, as Flesner claims, conceded that there is a question of material
fact as to specific causation. The context of Bayer's "concession" reveals that Bayer
was arguing in the alternative.
                                          -8-
App. 2002) ("Plaintiffs cannot manufacture a triable issue of fact through use of an
expert opinion . . . devoid of any basis, explanation, or reasoning."). Neither Dr.
Mayer's sparse objective medical evidence nor the conclusory remarks in his case-
specific expert-report form are sufficient to overcome the abuse-of-discretion standard
with which we are presented.

       First, Flesner fails to demonstrate that the district court abused its discretion
because Dr. Mayer cannot present any objective scientific evidence—other than
Flesner's slightly elevated CK level—that Baycol caused Flesner's injuries. In Dr.
Mayer's generic report, he stated that, while each is flawed, there are numerous tests
for diagnosing myopathy, including testing for increased CK and myoglobinuria
levels, muscle biopsies, and electromyography tests. He testified in his deposition,
however, that, other than testing for elevated CK levels, none of these scientific tests
was performed on Flesner. Further, he testified that Flesner's above-normal CK level
could have alternative causes and the elevation was so slight it would not, under the
standards of the American College of Cardiology, require discontinuation of Baycol
therapy out of concern for myopathy.

       In addition, although Flesner's CK levels were above normal in his first CK test,
the record does not contain a measure of Flesner's CK level prior to his taking Baycol.
Without this baseline reading, there is no evidence to suggest that this elevated level
has any link to Flesner's Baycol ingestion. This problem is exacerbated by the high
degree of variance exhibited in Flesner's post-Baycol CK readings. On September 18,
2001—approximately one month after he stopped taking Baycol—Flesner had a CK
level of 167, which, as Dr. Mayer testified, is within the normal range. But he
subsequently had three readings, again after he stopped taking Baycol, in which his
CK level was outside of the normal range.

      Finally, Dr. Mayer himself stated in his generic report that CK readings are an
"inaccurate and crude 'snapshot' of muscle damage" that "tell us little about
prognosis." Thus, the limited objective evidence available to Dr. Mayer was—as he
                                         -9-
describes it—a poor indicator of muscle damage, had alternative explanations, and
presented, at best, a weak causal link between Flesner's alleged injuries and his
ingestion of Baycol. We are not persuaded, therefore, that Flesner's slightly elevated
CK level calls into question the district court's decision that Dr. Mayer could not
present evidence that demonstrates, to a reasonable medical probability, that Baycol
contributed to Flesner's alleged injuries.

       Second, Dr. Mayer's conclusory remarks in his case-specific report are
insufficient to show that the district court abused its discretion in excluding his expert
testimony. In addition to noting Flesner's elevated CK level, Dr. Mayer based his
conclusion on his observations that: (1) Flesner's pain was of "new onset" with
ingestion of Baycol; (2) Dr. Mayer had no other explanation for the injury; (3) Flesner
suffered pain "reasonably contemporaneous" with ingesting Baycol; and (4) Flesner's
injury did not grow worse after he stopped taking Baycol.

       Dr. Mayer's deposition testimony, along with the remainder of the record, calls
into question his first and second observations in which he stated that the pain was of
"new onset" with Baycol ingestion and that there was "no other explanation" for
Flesner's pain. Flesner's medical history reveals a long battle with muscle pain, dating
back to 1988 when he suffered an on-the-job injury. Since that time, Flesner's doctors
have prescribed a number of pain medications to address Flesner's ongoing pain.
Thus, the record contains evidence that Flesner's pain was not of new onset and that
there were, indeed, alternative explanations for the pain. In his deposition, Dr. Mayer
acknowledged this history of muscle pain, but concluded that this prior pain was
"certainly of a different nature and character than it was after approximately August
2001." In this context, such conclusory statements without sufficient evidentiary
support do not call into question the district court's broad discretion in the area of
expert testimony.

      Dr. Mayer's third and fourth observations are best categorized as an argument
for causation by temporal association—the third observation addressing when the
                                       -10-
condition started, the fourth addressing when the condition stopped. Temporal
association, in this case, is not sufficient to prove it was "more likely than not," that
Baycol caused Flesner's injuries. We have held, "Under some circumstances, a strong
temporal connection is powerful evidence of causation." Bonner v. ISP Techs., Inc.,

, 931 (8th Cir. 2001). For example, in Bonner, we referenced Heller v.
Shaw Industries, Inc., 

(3d Cir. 1999), a case in which the Third Circuit
stated, "'if a person were doused with chemical X and immediately thereafter
developed symptom Y,'" this temporal relationship might constitute strong evidence
of causation. 

167 F.3d at 154). Flesner's case does not fit within
this narrow category. "The temporal relationship often will be only one of several
factors, and the weight to be given to the temporal relationship 'will differ depending
on the strength of that relationship.'" Bland v. Verizon Wireless, (VAW) LLC, 

, 899 (8th Cir. 2008) (quoting 

). In this case, the
additional factors on which Dr. Mayer relied are either unsupported by the record or
have alternative explanations. Further, Flesner has suffered muscle aches for many
years and taken a number of medications for a variety of ailments—some of them
contemporaneously with Baycol—thus reducing the strength of a causal link based on
a temporal relationship between his alleged pain and his Baycol ingestion. Given this,
temporal proximity does not render the district court's decision to disregard Dr.
Mayer's testimony an abuse of discretion.

        This case is not, as Flesner suggests, like Bonner, where there are "questions
of conflicting" expert 

; see also Andrews v. Foster Wheeler
LLC, 

, 239 (Cal. Ct. App. 2006) ("'[T]he court may not weigh the
plaintiff's evidence or inferences against the defendants' as though it were sitting as
the trier of fact.'") (citation omitted). Rather, it is a case in which Flesner failed to put
forth competent evidence with which to create a conflict. Without competent
evidence on both sides, there can be no "battle of the experts" in which a fact-finder
could weigh competing claims. Simply put, this case presents us with an expert
opinion based on conclusory statements, weak scientific evidence, and temporal
proximity in the face of alternative explanations. See Bushling v. Fremont Med. Ctr.,
                                            -11-


, 664 (Cal. Ct. App. 2004) ("[A]n expert opinion is worth no more
than the reasons and facts on which it is based."). Dr. Mayer's opinion on causation
simply lacks the factual basis to rise above the level of speculation. See 

("[A] court is not bound by expert opinion that is speculative
or conjectural."). Given the broad discretion afforded to district courts in matters of
expert testimony, we cannot find that the district court abused its discretion in finding
that Dr. Mayer could not competently testify as to medical causation in Flesner's case.
Flesner has therefore failed to establish the existence of an element of his
claims—causation—that he would have the burden of proving at trial. As a result,
summary judgment is appropriate and we affirm the district court. See 

.

                                            B.

      The district court also granted Bayer's motion for summary judgment on
Flesner's unjust-enrichment claim, finding that Flesner received what he bargained for
and therefore could not demonstrate that Bayer was unjustly enriched as a result of
Flesner purchasing Baycol. As with the previous claims, we affirm.

        Under California law, an unjust-enrichment plaintiff must show "receipt of a
benefit and unjust retention of the benefit at the expense of another." Lectrodryer v.
SeoulBank, 

, 883 (Cal. Ct. App. 2000). There is no question that
Bayer received a benefit when Flesner purchased Baycol. The issue is whether
retention of that benefit was unjust. See Marina Tenants Ass'n v. Deauville Marina
Dev. Co., 

, 328 (Cal. Ct. App. 1986) ("The 'mere fact that a person
benefits another is not itself sufficient to require the other to make restitution
therefor.'") (quoting Restatement (First) of Restitution § 1, cmt. c (1937)). We find
that it was not. The record illustrates not only that Flesner's cholesterol level fell after
he took Baycol, but, as our analysis in the previous section demonstrates, that there
is no competent medical evidence showing that Flesner suffered any harm as a result
of taking Baycol. Thus, he received the benefit of his bargain. In light of this, we
                                           -12-
affirm the district court's grant of summary judgment on Flesner's unjust-enrichment
claim. Peterson v. Cellco P'ship, 

, 323 (Cal. Ct. App. 2008)
("'There is no equitable reason for invoking restitution when the plaintiff gets the
exchange which he expected.'") (quoting Comet Theatre Enters., Inc. v. Cartwright,

, 83 (9th Cir. 1952)).

                                        IV.

      For the foregoing reasons, we affirm the judgment of the district court.
                      ______________________________




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