                        United States Court of Appeals
                               FOR THE EIGHTH CIRCUIT
                                           ___________

                                           No. 03-2651
                                           ___________

John Doe; Mary Doe, as Parents and      *
John & Mary Doe as Guardians on         *
behalf of John Doe, Jr.,                *
                                        *
             Appellants,                *
                                        *          Appeal from the United States
       v.                               *          District Court for the
                                        *          Southern District of Iowa.
Baxter Healthcare Corporation; Alpha *
Therapeutic Corporation; Bayer          *
Corporation,                            *
                                        *
             Appellees,                 *
                                        *
Cutter Biological, a Division of Miles, *
Inc.; Armour Pharmaceutical Company, *
                                        *
             Appellees.                 *

----------------------------------------

John Doe; Mary Doe, as Parents and      *
Guardians on behalf of John Doe, Jr.;   *
John Doe, Jr.,                          *
                                        *
            Appellants,                 *
                                        *
       v.                               *
                                        *
Cutter Biological, a Division of Miles, *
Inc.; Armour Pharmaceutical Company; *
Des Moines Plasma Center, Inc.;        *
Siouxland Plasma Center, now known as*
Gagnard and Marceaux, Sioux City, Inc.,*
                                       *
            Appellees.                 *
                                ___________

                            Submitted: April 15, 2004
                                Filed: August 24, 2004
                                  ___________

Before MORRIS SHEPPARD ARNOLD, MAGILL, and MURPHY, Circuit Judges.
                         ___________

MAGILL, Circuit Judge.

       Plaintiff-Appellants, John and Mary Doe (collectively, "the Does"), sued the
Defendant-Appellees, Armour Pharmaceutical Company ("Armour"), Alpha
Therapeutic Corporation ("Alpha"), Baxter Healthcare Corporation ("Baxter"), and
Bayer Corporation, f/k/a Cutter Biological ("Cutter"), in two separate actions in Iowa
state court. They claimed that one of the defendants had negligently caused their son,
John Doe, Jr. ("Doe Jr.") to become infected with Human Immunodeficiency Virus
("HIV") by allowing a product they knew carried a risk of infection to remain on the
market. Doe Jr. is a hemophiliac who has received various treatments for the disease,
including infusions of Factor VIII concentrate, which the defendants produced.

       This case presents three issues, all of which turn on whether the Does have
presented evidence sufficient to create a genuine question of fact regarding who
caused Doe Jr. to be infected with HIV. The first issue is whether, under traditional
negligence, the Does have presented enough evidence that any single defendant was
the but-for cause of Doe Jr.'s infection. The second issue is whether, under
alternative liability, the Plaintiffs have presented enough evidence that the four
defendants together are the only ones who could be responsible for Doe Jr.'s

                                         -2-
infection. If the four defendants are the only possible tortfeasors, then the Does argue
that each defendant has the burden of proving that it did not cause Doe Jr.'s injury.
The third issue is whether the Does can sustain a civil conspiracy cause of action
against the defendants. The resolution of this last issue turns on the resolution of the
first two issues; if the Does have created a genuine question of fact regarding
causation, then their civil conspiracy claim may go forward. The district court ruled
against the Does on all three issues, and the Does appeal.

      The district court had diversity jurisdiction to hear this case under 28 U.S.C.
§ 1332. This court has jurisdiction over the appeal under 28 U.S.C. § 1291. We
affirm.

                                           I.

A. Factual Background

       John Doe, Jr. was born on September 24, 1978. At ten months, physicians
diagnosed him as suffering from Hemophilia A, which results from a deficiency in
the production of a blood factor component known as "Factor VIII." Lack of Factor
VIII stops the blood from coagulating normally.

       There are various ways to treat Hemophilia A, and Doe Jr. has undergone
several of them at various times. The disease may be treated by supplementing levels
of the Factor VIII protein through infusions of whole blood, plasma, cryoprecipitate,
and Factor VIII concentrate. From November 24, 1979 to April 27, 1981, Doe Jr.
received cryoprecipitate infusions. Cryoprecipitate is the precipitate that forms when
plasma is frozen and then thawed. It is rich in Factor VIII, but contains other
components of the source plasma. Each cryoprecipitate treatment comes from a small
number of donors. According to one of the Does' experts, the cryoprecipitate used
in Iowa at the time was locally procured from single donors. On May 19, 1980, Doe

                                          -3-
Jr. received his first infusion of Factor VIII concentrate. Factor VIII concentrate is
made from pooled human plasma from many different donors from across the
country. Manufacturers separate components of the plasma and isolate the Factor
VIII protein for use in the therapy. Factor VIII concentrate is made from the plasma
of hundreds or thousands of donors, so the number of donors in any single dose is
quite large. Doe Jr. continued to receive Factor VIII concentrate infusions
manufactured by various companies until January 1985. After that month, he
received only heat-treated Factor VIII concentrate or monoclonal factor concentrates.
Neither of these last methods of treatment carry any risk of HIV infection. The heat-
treatment destroys the HIV virus, and monoclonal factors are derived from non-blood
sources that cannot carry the disease.

       Doe Jr. tested positive for HIV in July 1987. The parties agree that his infection
occurred during a single infusion, and that it is not possible to identify which
particular infusion caused his infection. Instead, the Does attempted to establish,
using expert testimony, the period during which Doe Jr. was infected. They presented
expert testimony that Doe Jr. received treatments that exposed him to some risk of
HIV exposure beginning in November 1979 and continuing through January 1985.
There is evidence that the risk of exposure from cryoprecipitate treatments between
November 1979 and May 1981 was very low. They also presented expert testimony
that Doe Jr.'s risk of exposure greatly increased when he began receiving treatments
of Factor VIII concentrate on May 19, 1980. The Does also offered evidence that
Doe Jr. was not infected by a heat-treated Factor VIII concentrate treatment or a
monoclonal concentrate treatment.1 According to medical records, this places the
date of Doe Jr.'s infection between 1979 and January 1985, the period during which
Doe Jr. received cryoprecipitate treatments and Factor VIII concentrate treatments
that had not been heat-treated. The Does spend much of their effort trying to


      1
       The defendants agree that Doe Jr. could not have been infected once he began
treatment using heat-treated concentrate and monoclonal concentrate.

                                          -4-
establish which defendants supplied the Factor VIII concentrate between May 1980
and January 1985. Although they have named the relevant suppliers of Factor VIII
concentrate, they have not named the manufacturers of the cryoprecipitate as
defendants.

      The Does rely on hospital records that indicate the source of the concentrate
with which Doe Jr. was treated. According to those records, Doe Jr. received Factor
VIII concentrate prescriptions from three manufacturers: Cutter, Armour, and Alpha.
The evidence indicates he received nineteen prescriptions from May 1980 to
November 1984. He received two prescriptions for Alpha products, on May 20, 1980
and June 15, 1980. Except for those two dates, all Doe Jr.'s prescriptions from May
1980 to September 6, 1983 were for Cutter's factor concentrate. Thereafter, from
December 2, 1983 to November 19, 1984, Doe Jr. used the factor concentrate
manufactured by Armour. Complicating this issue, the Does' experts contend that the
records are incomplete. They estimate that he received many more doses of Factor
VIII concentrate than the surviving records reflect.

       The Does' expert medical testimony further limits the dates of possible
infection. They presented statements by four experts. James Mosley, M.D., asserted
that Doe Jr. was infected after the middle of 1983. William Robinson, M.D., opined
that he was infected around February 1983. Roger Grimson, Ph.D., was of the
opinion that Doe Jr. was infected in or after August 1983. Finally, Robert Remis
provided probabilities of infection for each relevant year. He said that there was a
65% chance that Doe Jr. was infected between 1983 and 1985. He also said there was
a 5% chance of infection in 1980, 5% in 1981, and 25% in 1982.2 The defendants

      2
       Defendants claim that Doe Jr.'s physician, Thomas Kisker, M.D., gave expert
testimony indicating his opinion was that Doe Jr. was infected in the fall of 1982.
This position differs from the opinions of the Does' other experts. However, Dr.
Kisker was not recognized by the district court as a qualified expert; he testified as
Doe Jr.'s personal physician. As he noted in his testimony, an "infection disease

                                         -5-
presented their own experts, who asserted that the infection probably occurred before
August 1982.

       In addition, the Does have presented an expert's declaration asserting that
Alpha, Armour, Baxter, and Cutter were the only players in the Factor VIII
concentrate market in Iowa at the relevant time. The expert's declaration states the
four named defendants in this case "had 94.5% of the national Factor VIII market in
1980 . . . , 93% of the national Factor VIII market in 1982 . . . , and 88% of the market
in 1984." Summ. J. App. at A-204.3 The same declaration indicates that the other
purported market players did not distribute to Iowa during the relevant period.

        Defendants claim they have presented contrary evidence that shows they were
not the only manufacturers in the market at the time Doe Jr. was using Factor VIII
concentrate. They represent to the court that there were seven other market players
at the time: the American Red Cross ("Red Cross"); Abbott Laboratories ("Abbott");
New York Blood Center; Scripps Laboratories ("Scripps"); Parke-Davis; Squibb; and
Michigan State Laboratories. This claim is almost entirely unsupported by the record
citations defendants have provided. For every purported market player except the
Red Cross, the defendants rely for their claims solely on the depositions of Fred
Feldman and Allan Brownstein. Dr. Feldman, however, represents only that certain
other manufacturers were in the business of making factor concentrate in late 1974.
His testimony is unhelpful. Brownstein is perhaps less helpful still. Brownstein gave


person" would better be able to answer questions regarding the precise date of Doe
Jr.'s infection. Summ. J. App. at A-101. The Does' other experts dismissed his
estimate as based on false premises.
      3
       Apparently there was some controversy over the timing of this expert report.
The district court noted that there was some question whether the expert's report
would be admitted. Doe v. Baxter Healthcare Corp., 178 F. Supp. 2d 1003, 1014
(S.D. Iowa 2001). The court did not resolve this issue, however, and the defendants
do not press it on appeal.

                                          -6-
testimony that some other companies were producing Factor VIII concentrate in the
late 1970s. It is clear from his deposition transcript that his memory is limited, and
he makes no representations regarding production in the 1980s or these companies'
distribution of their product. Thus, defendants point to no evidence that other
companies were in the Factor VIII concentrate market during the early to middle
1980s.

       The most important factual dispute concerns whether the Red Cross provided
some Factor VIII concentrate to Doe Jr. during the period before 1985. The Does
admit that on one occasion they obtained Factor VIII concentrate distributed to the
University of Minnesota by the Red Cross. What are contested are the dates of these
purchases. The dates are important because, as of 1985, the Red Cross distributed
only heat-treated Factor VIII concentrate, which the parties admit cannot transmit
HIV. The Does provide conflicting evidence on this point. Mrs. Doe testified in her
deposition that she believed that she purchased the Red Cross factor concentrate
before 1985. Summ. J. App. at A-24. However, in a later declaration, Mrs. Doe
stated that she had reviewed her records and they refreshed her recollection that she
purchased the Red Cross factor concentrate in 1985. The Does include as support
copies of the records of their son's treatment at the University of Minnesota. The
records confirm that he began treatment at the University of Minnesota on June 10,
1985. Thus, viewing the facts in the light most favorable to the Does, it appears that
Mrs. Doe's earlier testimony was mistaken, and Doe Jr. did not receive factor
concentrate from the Red Cross until after they had begun heat-treating their product.

      In addition, the Does presented evidence that all four defendants conspired to
keep factor concentrate they knew to be contaminated with HIV on the shelves after
they had decided to change their production method to eliminate the risk of infection.
The district court ruled that the Does had presented sufficient evidence to survive
summary judgment on that claim, provided that negligence could be the underlying
offense. Later, the Iowa Supreme Court held, in answer to a certified question in

                                         -7-
another case, that negligence can be the underlying offense upon which a civil
conspiracy claim is based. The defendants do not challenge the sufficiency of the
Does' evidence that there was a conspiracy, but instead seek to avoid liability for civil
conspiracy on the ground that the Does cannot establish that any single defendant
caused Doe Jr.'s injury and thus cannot establish that there was an underlying tort.

B.    Procedural Background

       The Does filed two negligence actions in Iowa state court in 1996. The
defendants removed them to the United States District Court for the Southern District
of Iowa based on diversity jurisdiction. The Judicial Panel on Multidistrict Litigation
transferred the cases to the United States District Court for the Northern District of
Illinois for coordinated pretrial proceedings. In 1999, the cases were sent back to the
Southern District of Iowa. After discovery, the defendants sought summary judgment
on the basis that the Does could not establish causation and that in Iowa a civil
conspiracy claim cannot be predicated upon an underlying negligence claim. The
district court granted summary judgment on the negligence claims, holding that the
Does had failed to create a genuine issue of material fact on the question who caused
Doe Jr.'s infection. The district court withheld judgment on the civil conspiracy claim
because the Iowa Supreme Court had before it a certified question in another case.
In Wright v. Brooke Group Ltd., 652 N.W.2d 159 (Iowa 2002), the Iowa Supreme
Court held that plaintiffs can base a civil conspiracy claim on a non-intentional
underlying tort. On June 3, 2003, the district court granted defendants' motion for
summary judgment on the alternate basis that the Does could not establish the
underlying tort. The Does timely appealed.

                                           II.

      This court reviews the district court's grant of summary judgment de novo.
Dico, Inc. v. Amoco Oil Co., 340 F.3d 525, 528-29 (8th Cir. 2003). Summary

                                          -8-
judgment is appropriate only where no genuine issue of material fact exists and the
moving party is entitled to judgment as a matter of law. Anderson v. Liberty Lobby,
Inc., 477 U.S. 242, 250 (1986). The party opposing summary judgment "'must
present more than a scintilla of evidence and must advance specific facts to create a
genuine issue of material fact for trial.'" Dico, 340 F.3d at 529 (quoting F.D.I.C. v.
Bell, 106 F.3d 258, 263 (8th Cir. 1997)).

                                          III.

       The Does first claim that the district court erred by dismissing their claim under
a traditional negligence theory of liability. We must decide whether the Does
presented enough evidence respecting which one defendant caused Doe Jr. to become
infected with HIV to allow a jury to impose liability. The Does presented evidence
that shows Doe Jr. was infected between 1979—when he started using
cryoprecipitate—and January 1985—when he started using a safe, heat-treated
version of Factor VIII concentrate. They also presented expert testimony stating that
the infection most likely occurred during 1982, 1983, or 1985. The Does also
presented evidence that they used the Factor VIII concentrate product of three of the
named defendants: Armour, Alpha, and Cutter.4 All parties agree that there is no way
to determine the precise injection that infected Doe Jr.5 The only evidence that can
distinguish the three defendants are the dates Doe Jr. used their products and the
expert statements regarding the date of infection.


      4
       The Does concede that they do not have a claim in traditional negligence
against defendant Baxter because they have no evidence that Doe Jr. used a Baxter
product. They maintain their claims against Baxter only under the alternative liability
theory and the civil conspiracy charge.
      5
        In some cases of HIV infection, the event of infection is followed shortly by
an illness that experts may use to infer the date of infection. The parties agree that
Doe Jr. did not exhibit an incidental illness of this sort.

                                          -9-
        A defendant's breach of its duty of care is actionable negligence only if the
breach is the proximate cause of a plaintiff's injury. Cedar Falls v. Cedar Falls Sch.
Dist., 617 N.W.2d 11, 17 (Iowa 2000). Proximate cause has two elements: "(1) the
defendant's conduct must have in fact caused the damages; and (2) the policy of the
law must require the defendant to be legally responsible for them." Id. To establish
the first element of proximate causation, the Does must show that their son's damages
would not have occurred but-for a defendant's negligence. Id.

       The Does' claim founders on the shoals of the but-for requirement, for it is
conceded by the Does that there is no way to identify the moment of infection. The
best they can hope to do is narrow the potential dates and show which companies
provided the product during that period. Their experts have not narrowed the
potential dates of infection so far that a rational jury could conclude that the conduct
of one of the defendants was the but-for cause of Doe Jr.'s infection. The best that
can be said for the evidence is that there is a strong likelihood that either Cutter or
Armour supplied the Factor VIII concentrate that infected Doe Jr. But the evidence
provides no means of distinguishing between these two defendants. Consequently,
even taking the expert statements proffered by the Does as true, a jury would be
required to speculate in order to find one of the defendants liable for Doe Jr.'s
damages.

      The Does argue that the court should not require them to prove any single
defendant was a but-for cause. They argue for the lesser standard articulated by the
Iowa Supreme Court in Huber v. Watson, 568 N.W.2d 787 (Iowa 1997). That court
held that "[i]n cases involving exposure to asbestos, 'a reasonable inference of
exposure to a defendant's asbestos-containing product, coupled with expert testimony
regarding asbestos fiber drift and the cumulative effects of exposure to asbestos, is
enough to prove proximate cause.'" Id. at 790 (quoting Beeman v. Manville Corp.
Asbestos Disease Comp. Fund, 496 N.W.2d 247, 254 (Iowa 1993)). The "test is
whether a jury could logically make the necessary inference of the causal connection

                                         -10-
between defendant's action and the plaintiff's injury." Id. Under this standard, the
Does argue, the evidence would support a jury verdict in their favor because their
expert testimony narrows the range of possible dates of infection and would allow a
jury to base its judgment on probability judgments of experts that one defendant or
another was a substantial cause of Doe Jr.'s injuries.

       The Does' reliance on Huber's reasoning is misplaced. Huber and all the cases
upon which it relies concern liability for injuries caused by asbestos exposure. The
crucial difference between asbestos exposure and exposure to HIV is that the effects
of asbestos exposure are cumulative. Hence, incidents of asbestos exposure are
concurrent causes of a plaintiff's injuries. The parties and experts all admit that HIV
infection does not work in the same way. Doe Jr. was infected on a particular
occasion. Doe Jr.'s separate infusions were not concurrent causes of his HIV
infection. Plaintiffs are relieved of the need to show that a defendant was a but-for
cause of an injury only where the "conduct of two or more persons 'is so related to an
event that their combined conduct, viewed as a whole, is a but-for cause of the event,
and the application of the but-for rule to them individually would absolve all of
them.'" Spaur v. Owens-Corning Fiberglass Corp., 510 N.W.2d 854, 858 (Iowa 1994)
(quoting W. Page Keeton, Prosser and Keeton on the Law of Torts § 41, 268 (5th ed.
1984)). Since the parties admit that concurrent causation is not at issue in this case,
the Does are not relieved of the need to distinguish between the defendants and show
that one was the but-for cause of Doe Jr.'s infection.

      Accordingly, we will affirm the district court's determination that the Does
cannot sustain their claim under traditional negligence.

                                         IV.

      The Does seek to have this court apply a widely accepted exception to the
requirement that they prove which negligent defendant caused Doe Jr. to be infected

                                         -11-
with HIV.6 Under an alternative liability approach to causation, the plaintiff still must
show that one of the defendants caused his injury, but "the burden of proof as to
which actor caused the harm shifts to the defendants because there is uncertainty as
to which of them caused the injury." Mulcahy v. Eli Lilly & Co., 386 N.W.2d 67, 72
(Iowa 1986). If the court found alternative liability applicable, it would not matter
that the plaintiffs cannot pinpoint the date of infection or the manufacturer which
supplied the tainted Factor VIII concentrate. Instead, the plaintiffs might prevail on
summary judgment if they can create a genuine question of material fact whether only
the named defendants could have caused Doe Jr. to contract HIV, even if they cannot
show which one of the defendants did so.

       We begin by considering whether it is appropriate under Iowa law to apply the
alternative liability theory at all. Under diversity jurisdiction and applying Iowa law,
we must endeavor to decide the case as the Iowa Supreme Court would decide it.
Rucci v. City of Pacific, 327 F.3d 651, 652-53 (8th Cir. 2003). We are bound by the
decisions of the Iowa Supreme Court. Id. at 652. Where the Iowa Supreme Court has
not addressed an issue, we must determine what rule the Iowa Supreme Court would
apply. Id. at 652-53. Statements made by the Iowa Supreme Court are instructive.
So, too, are rulings by inferior state appellate courts. Id. at 653.

       The Iowa Supreme Court has neither adopted the alternative liability theory nor
ruled it out, so we are faced with predicting whether that court would apply
alternative liability in this case. There are no Iowa Court of Appeals decisions on the
topic. However, the Iowa Supreme Court did discuss the theory of liability at some
length in Mulcahy, 386 N.W.2d at 72-74. In that case, the Supreme Court faced a

      6
        The exception had its origin in the California Supreme Court decision in
Summers v. Tice, 199 P.2d 1 (Cal. 1948). It has been followed by courts in several
states in the context of product liability suits. See, e.g., McGuinness v Wakefern
Corp., 608 A.2d 447 (N.J. 1991); Minnich v. Ashland Oil Co., Inc., 473 N.E.2d 1199
(Ohio 1984); Abel v. Eli Lilly & Co., 343 N.W.2d 164 (Mich. 1984).

                                          -12-
certified question from a federal district court asking whether it would adopt three
nontraditional theories of tort liability on certain established facts. While the Iowa
Supreme Court did not, in the end, adopt a position on alternative liability, the case
bears close attention for its detailed discussion of nontraditional theories of
negligence.

       The product under review in Mulcahy was a synthetic estrogen compound
known as DES. Id. at 69. DES causes injury to children still in the womb when
ingested by their mothers. DES can also cause difficulties for the grandchildren of
women who took the drug. As a consequence, victims of DES did not recognize they
had been injured until years—and in some cases decades—later. Plaintiffs in DES
lawsuits seldom could present evidence concerning the manufacturer of the particular
doses their mothers or grandmothers took. At the time of concern in Mulcahy, there
were some 200 manufacturers and distributors of DES nationally. The Mulcahy
plaintiffs sought to establish liability by appealing to three different
theories—alternative liability, enterprise liability,7 and market share liability. The
court held that neither alternative liability nor enterprise liability applied on the facts
before it. Its treatment of market share liability, however, was more direct and more
hostile.

       The Iowa Supreme Court rejected the market share liability theory on broad
policy grounds. Under market share liability, as fashioned by the California Supreme
Court in Sindell v. Abbott Laboratories, 607 P.2d 924 (Ca. 1980), a plaintiff need not
join all potential defendants to benefit from burden shifting. There need be no


      7
        Enterprise liability has the following elements: (1) the product that caused the
injury was manufactured by one of a few defendants; (2) the defendants all knew of
the risks the product posed and together had the ability to reduce those risks; and (3)
the defendants failed to take those steps, choosing instead to push responsibility for
taking action onto a trade association. See, e.g., Burnside v. Abbott Laboratories, 505
A.2d 973, 984 (Pa. Super. Ct. 1985). Enterprise liability is not at issue in this case.

                                           -13-
assurances whatsoever that the defendants who actually end up paying damages for
an injury played any role in causing the injury. A plaintiff must only join
manufacturers of a substantial share of the product and meet her burden of proof on
the other negligence elements. The burden then shifts to the defendants to prove they
could not have issued the particular product that caused the injury. For any
defendants who fail to meet their burden, the court "fashions a 'market share' theory
to apportion damages according to the likelihood that any of defendants supplied the
product by holding each defendant liable for the proportion of the judgment
represented by its share of that market." Mulcahy, 386 N.W.2d at 75 (quotation
omitted). The Iowa Supreme Court objected that all this theory requires of a plaintiff
is proof of negligence "in the air," and held that such would not suffice. Id. at 76.
The link between the defendant and the injurious act under the market share theory
is too attenuated.

       The alternative liability theory does not exhibit the same faults as the market
share liability theory. The Iowa Supreme Court treated the alternative liability theory
less dismissively, holding only that it did not apply under the facts as presented. The
court noted that one version of the alternative liability theory "still requires plaintiffs
to prove they have been harmed by the conduct of one of the defendants." Id. at 74.
Thus, there is a closer link between tortfeasor and injury under alternative liability
than under market share liability. The plaintiff under alternative liability has the
burden of narrowing the field of potentially liable defendants to "'all the actors who
may have caused the injury in fact.'" Id. (quoting Abel v. Eli Lilly & Co., 343
N.W.2d 164, 173 (Mich. 1984)). According to the Iowa Supreme Court, "[p]laintiffs
also have the burden of showing that all the defendants have acted tortiously, and that
plaintiffs, through no fault of their own, are unable to identify which actor caused the
injury." Mulcahy, 386 N.W.2d at 74. Only at this point does the burden shift under
alternative liability, requiring defendants to prove they did not manufacture the
injurious product. Thus, under alternative liability, the plaintiffs have a much stiffer
burden than under market share liability, and the difference addresses the precise

                                           -14-
concerns the Iowa Supreme Court expressed in rejecting market share liability.
Plaintiffs may not simply prove negligence is "in the air," but rather must target all
the companies that might have been liable and prove that each had a duty of care that
it breached. This rule is a far cry from market share liability, which simply apportions
liability to market actors who cannot prove they did not cause a particular injury.

        While we think, based on Mulcahy, that the Iowa Supreme Court would adopt
the alternative liability theory and give it the contours discussed in that case if
presented with the right facts, we need not decide that issue because we do not
believe that it would do so on the facts here presented. To hold the theory applies,
we would have to hold that the district court erred in determining that the Does did
not succeed in presenting enough evidence that they had brought all potential
defendants to court. The district court held that the Does' claim fails because they did
not negate the manufacturers of the doses of cryoprecipitate as potential defendants.
To do so, they would have to have presented enough evidence to convince a rational
jury that the cryoprecipitate manufacturers could not have caused Doe Jr.'s injury. It
is not sufficient that they present enough evidence to convince a rational jury that the
cryoprecipitate manufacturers did not cause his injury. The defendants also argue that
the Does cannot prevail for the additional reason that Doe Jr. received Factor VIII
concentrate treatments manufactured by the Red Cross and that the Does did not
negate these doses as the cause of Doe Jr.'s infection. In our view, it is only the Does'
failure to exclude the manufacturers of cryoprecipitate as potential defendants that is
fatal to their claim.

       The Does have presented sufficient evidence to convince a rational jury that the
Red Cross-manufactured Factor VIII concentrate could not have infected Doe Jr. In
Mulcahy, the Iowa Court held that alternative liability could not apply because
"[plaintiffs] do not possess evidence to negate marketing of DES in Ames by other
manufacturers." Id. at 74. The Does, unlike the plaintiffs in Mulcahy, have
substantial evidence that the Factor VIII concentrate manufactured by the Red Cross

                                          -15-
did not cause their son's infection. This feature of the case distinguishes it from
Mulcahy and supports allowing the plaintiffs to go forward on an alternative liability
theory. Defendants rely on Mrs. Doe's deposition testimony claiming that her son
received a non-heat-treated infusion of Factor VIII concentrate from the Red Cross
before 1985. If true, the treatment would be a potential source of the infection.
However, Mrs. Doe has since reviewed the medical records from the University of
Minnesota, where the Red Cross treatment occurred, and determined that she was
mistaken about the date. The Does have provided their son's records from the
University of Minnesota, and they confirm that he first received treatments there in
1985, after the Red Cross started heat-treating its Factor VIII concentrate.
Consequently, on both these points the Does have presented evidence sufficient for
a rational jury to conclude that the Red Cross could not have caused Doe Jr.'s
infection. The defendants are not entitled to summary judgment on this basis.

       The Does have not, however, met their burden under the summary judgment
standard with respect to Doe Jr.'s cryoprecipitate treatments. The district court
properly determined that the Does' evidence that Doe Jr.'s cryoprecipitate treatments
could not have caused his infection was insufficient as a matter of law. The facts
related to these treatments are sparse. Doe Jr. received several treatments with
cryoprecipitate between November 24, 1979 and April 27, 1981. On May 19, 1980,
Doe Jr. began using Factor VIII concentrate, and by April 27 the next year, he made
the switch permanent. Unlike factor concentrates which result from blending
multiple donor samples together, cryoprecipitate is made from the blood of a very few
donors. Thus the risk posed by any use of cryoprecipitate is much lower than that
posed by an application of factor concentrate. The treatments are not without risk,
however. The Does presented an expert declaration by Dr. Donald Francis, M.D.,
which briefly addressed the likelihood that Doe Jr. was infected by cryoprecipitate.
According to Dr. Francis, the cryoprecipitate posed "very little" risk of infection to
Doe Jr. Presumably based in part on this same view of the risk posed by the
cryoprecipitate treatments, other experts testified that Doe Jr.'s infection most likely

                                         -16-
occurred after he stopped receiving those treatments. This is the sole evidence
provided to negate the cryoprecipitate as the agent of Doe Jr.'s infection. The experts'
proposed testimony cannot negate the manufacturers of the cryoprecipitate as the
actors who caused Doe Jr.'s infection; it can only cast strong doubt on them as
culprits. Mulcahy requires that plaintiffs clear a much higher hurdle. While it is
evident that the Does have created a genuine question of fact that the cryoprecipitate
treatments did not cause Doe Jr.'s infection, they have not created a genuine question
of fact that they could not have caused the infection, which is the standard favored
in Mulcahy. It is a difficult standard to meet, but it is the cost of avoiding proof that
some particular, single defendant was the but-for cause of Doe Jr.'s injury under Iowa
law. We believe the Iowa Supreme Court favors a rule that keeps liability for
negligence moored closely to causation, as its discussion renouncing market share
liability makes clear. Accordingly, we cannot say that the Does have created a
genuine question of material fact as to whether all the potential defendants have been
named, and we affirm that aspect of the district court's order.

                                           V.

      The Does also appeal the district court's separate order granting summary
judgment in favor of all defendants on the Does' civil conspiracy claim. Given our
conclusion that the Does did not present enough evidence that any single defendant
caused Doe Jr.'s injury, it follows that the district court properly dismissed the civil
conspiracy claim as well. A civil conspiracy is an agreement between two or more
people to commit a wrong against another person. Wright v. Brooke Group Ltd., 652
N.W.2d 159, 172 (Iowa 2002). The conspiracy alone is not actionable. Id. Only acts
taken in furtherance of the conspiracy that cause some injury to the plaintiff can be
the basis of a civil conspiracy claim. Id. The district court held that the Does had
presented sufficient evidence of a conspiracy involving the defendants to withstand




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summary judgment. But, as we held above, they have not presented sufficient
evidence that any of the defendants actually caused Doe to become infected with
HIV. Without such evidence, the Does' civil conspiracy claim sinks as well.

                                         VI.

       For the reasons provided above, we affirm the decision of the district court in
all respects.
                       ______________________________




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