                IN THE SUPREME COURT OF IOWA
                              No. 07–1595

                          Filed October 9, 2009


GLEN D. JAHN, LISA A. JAHN and
GLEN D. JAHN and LISA A. JAHN as Guardians
and Next Friends of CASSIE L. JAHN,

      Plaintiffs,

vs.

HYUNDAI MOTOR COMPANY and HYUNDAI
MOTOR AMERICA, Inc., d/b/a/ HYUNDAI MOTOR
AMERICA,

      Defendants.


      Certified questions of law from the United States District Court for

the Southern District of Iowa, Thomas J. Shields, Chief United States

Magistrate Judge.



      Federal district court certified two questions concerning a claim for

enhanced injuries arising out of a products liability action. CERTIFIED

QUESTIONS ANSWERED.


      James D. Bruhn of Farwell & Bruhn, Clinton, for plaintiffs.



      Richard J. Sapp, Debra L. Hulett, John T. Clendenin, and

Matthew R. Eslick of Nyemaster, Goode, West, Hansell & O’Brien, P.C.,

Des Moines, for defendants.
                                      2

APPEL, Justice.

      The United States District Court for the Southern District of Iowa

certified two questions to this court arising out of a products liability

action. The two certified questions are:
      1.     Will the Iowa Supreme Court adopt sections 16 and 17
             of the Restatement (Third) of Torts: Products Liability
             governing liability for enhanced injury, specifically,
             including rules of joint and several liability and
             comparative fault of joint tortfeasors under sections
             16(d) and 17, and defining burdens of proof under
             sections 16(b) and 16(c)?
      2.     Under the Iowa Comparative Fault Act, may the fault
             of a released party whose negligence was a proximate
             cause of the underlying accident and of the plaintiff’s
             injuries be compared by the jury on plaintiff’s
             enhanced injury claim against the product defendant?
For the reasons expressed below, we answer “yes” to all aspects of both

questions and elaborate on our answers to provide guidance to the

federal court.

      I. Factual Background and Procedural History.

      For purposes of the certified questions presented in this case, there

are no factual disputes.     The accident that gave rise to this litigation

occurred when a vehicle driven by Grace Burke blew through a stop sign

at an intersection in Clinton, Iowa and struck an automobile operated by

Glen Jahn.       After impact, the front, driver-side airbag in the vehicle

driven by Jahn, a Hyundai Elantra, allegedly failed to deploy. As a result

of the accident, Jahn sustained multiple serious injuries including

fractures of the skull, left hip, knee, right femur, right tibia, right ankle,

and arch of the foot. Jahn also allegedly suffered a closed head injury.

      Jahn reached a settlement with Burke and her insurance carrier

prior to filing the present action against Hyundai Motor America (HMA).

In the present action, the Jahns allege that the failure of the airbag in

their Hyundai Elantra to deploy upon impact caused Jahn enhanced
                                       3

injuries that could have been avoided absent the alleged product defect.

The Jahns’ products liability claim is founded on res ipsa loquitur, strict

liability, and breach of warranty.

         The issue presented here is whether Burke’s fault may be

compared by the jury when evaluating the Jahns’ products liability claim

against HMA. The Jahns admit that Burke is a “released party” under

the Iowa Comparative Fault Act. Iowa Code §§ 668.2, .7 (2003). Further,

the Jahns admit that Burke’s fault was a proximate cause of the accident

and a proximate cause of Jahn’s injuries. They, nevertheless, assert that

Burke’s fault may not be compared by the jury in the products liability

action against HMA.

         HMA filed a motion to certify questions of law to this court seeking

definitive rulings related to whether sections 16 and 17 of the

Restatement (Third) of Torts: Products Liability should apply in this case

and, if they do, how these provisions should apply to the facts and

circumstances presented here.        The Jahns joined in the motion.     The

district court granted the motion and certified two questions for our

determination.

         II. Discussion.

         A. Position of the Parties. HMA and the Jahns both agree that

the court should adopt sections 16 and 17 of the Restatement (Third) of

Torts:    Products Liability.   The parties differ dramatically, however, on

the proper interpretation of these provisions.

         According to HMA, sections 16 and 17 of the Restatement treat

products liability cases, including those involving enhanced injuries, like

any other case involving multiparty defendants whose fault must be

compared under Iowa’s Comparative Fault Act.
                                          4

       On the other hand, the Jahns argue that to the extent there are

injuries   that    would    have    occurred     from    the    crash    alone,    the

manufacturer is not liable for these harms.                    In contrast, if the

manufacturer cannot apportion the injuries, it is liable for all of the

injuries suffered by the plaintiff without application of comparative fault.

       B. Theory of Enhanced Injury Liability. 1

       1. Background. As late as 1966, courts rejected the notion that a

product manufacturer could be liable for defective products where the

negligence of another party was the cause of the underlying accident.

See generally Evans v. Gen. Motors Corp., 359 F.2d 822 (7th Cir. 1966),

overruled by Huff v. White Motor Corp., 565 F.2d 104, 110 (7th Cir. 1977).

The rationale was generally that manufacturers could be held liable only

for injuries resulting from intended use.              Id. at 825.      Despite the

forseeability of automobile collisions, they were not considered an

intended use. Id.

       In the seminal case of Larsen v. General Motors Corp., 391 F.2d

495 (8th Cir. 1968), the Eighth Circuit broke new ground.                  The court

noted, “No rational basis exists for limiting recovery to situations where

the defect in design or manufacture was the causative factor of the

accident, as the accident and the resulting injury . . . all are foreseeable.”

Larsen, 391 F.2d at 502. As a result, the Larsen court saw no reason

“why the manufacturer should not be held to a reasonable duty of care in

the design of its vehicle consonant with the state of the art to minimize

the effect of accidents.” Id. at 503.




       1The  plaintiffs dispute the use of the nomenclature “enhanced injury.” The
phrase is simply a convenient label, however, and has no independent significance. It
represents that portion of total damages for which a product manufacturer may be
liable in a multiparty action involving an initial cause unrelated to a product defect.
                                      5

      The Larsen approach was further refined by the Fourth Circuit in

Dreisonstok v. Volkswagenwerk, A. G., 489 F.2d 1066 (4th Cir. 1974). In

Dreisonstok, the court stated that a manufacturer’s duty extended only

to designing a vehicle to avoid “ ‘unreasonable risk of injury in the event

of a collision.’ ” Dreisonstok, 489 F.2d at 1070 n.11 (quoting Larsen, 391

F.2d at 502). See generally Barry Levenstam & Daryl J. Lapp, Plaintiff’s

Burden of Proving Enhanced Injury in Crashworthiness Cases: A Clash

Worthy of Analysis, 38 DePaul L. Rev. 55, 61 (1988) [hereinafter

Levenstam & Lapp].

      Under an enhanced injury theory, the product defect is not the

cause of the initial accident. As a result, the manufacturer cannot be

held liable for injuries arising out of the initial collision.         The

manufacturer, however, is liable for enhanced injuries over and above

the injuries caused by the initial collision.

      2.    Burden of proof.   A question arises regarding the plaintiff’s

burden of proof to sustain an enhanced injury claim. One line of cases,

often named the Huddell approach after a leading case, holds that the

plaintiff has the burden of showing that the “sole cause” of the enhanced

injury was a product defect. See Huddell v. Levin, 537 F.2d 726 (3d Cir.

1976).     According to the court in Huddell, a plaintiff in an enhanced

injury case must prove: (1) the existence of a safer, practicable,

alternative design, (2) the extent of the injuries the plaintiff would have

suffered had the alternative design been used, and (3) “some method of

establishing the extent of enhanced injuries attributable to the defective

design.” Id. at 737–38.

      The Huddell approach was elaborated upon in Caiazzo v.

Volkswagenwerk A. G., 647 F.2d 241 (2d Cir. 1981).        In Caiazzo, the

court stressed that the plaintiff had the burden of showing not only the
                                        6

fact of enhanced injury but the extent of enhanced injuries attributable

to the defective design. Caiazzo, 647 F.2d at 250. According to Caiazzo,

if the plaintiff cannot identify what portion of the injury occurred as a

result of the design defect by a preponderance of evidence, the enhanced

injury claim fails. Id. at 251.

      The practical impact of the Huddell rule as applied in Caiazzo is

that the plaintiff has the burden of apportioning the loss and loses his

enhanced injury claim if he fails to offer proof of apportionment. This

approach has been adopted in a number of cases. See, e.g., Barris v.

Bob’s Drag Chutes & Safety Equip., Inc., 685 F.2d 94, 99 (3d Cir. 1982)

(applying Pennsylvania law); Dawson v. Chrysler Corp., 630 F.2d 950,

959–60 (3d Cir. 1980) (applying New Jersey law). The Huddell approach

pulls apart and segregates the injuries and, as a result, principles of joint

and several liability do not apply in an enhanced injury case.

      A second line of cases imposes a less stringent proof requirement

on plaintiffs. Under this second line of cases, often referred to as the

Fox-Mitchell approach, the plaintiff must prove only that the product

defect was a “substantial factor” in creating damage greater than that

attributable   solely   to   the   underlying   accident.   See Mitchell v.

Volkswagenwerk, AG, 669 F.2d 1199, 1206 (8th Cir. 1982); Fox v. Ford

Motor Co., 575 F.2d 774, 787 (10th Cir. 1978). If the factfinder is unable

to segregate the harm caused by the initial collision from the harm

caused by the product defect, the manufacturer is liable for the entire

injury. Mitchell, 669 F.2d at 1206.

      The rationale of the Fox-Mitchell approach is generally that injuries

are often indivisible and that the Huddell approach imposes an unfair

burden by requiring the plaintiff to “prove the impossible.” Id. at 1203–

04. In addition, the Huddell approach is criticized as inconsistent with
                                      7

orthodox concurrent tortfeasor theory in which apportionment of injuries

is not required to impose joint liability for the entire injury.   Fox, 575

F.2d at 787; see also Levenstam & Lapp, 38 DePaul L. Rev. at 70.

         As is apparent, the Fox-Mitchell approach, which has been adopted

in a number of cases, see, e.g., Fouche v. Chrysler Motors Corp., 646 P.2d

1020, 1024–25 (Idaho Ct. App. 1982); Lee v. Volkswagen of Am., Inc., 688

P.2d 1283, 1288 (Okla. 1984), produces the opposite result of Huddell in

the event of indivisible injury.     Under Huddell, the plaintiff has the

burden of showing apportionment, usually through expert testimony,

and has no enhanced injury claim if the claim is indivisible.

         3. Application of comparative fault. Another disputed issue relates

to the relationship between enhanced injury claims and comparative

fault.    The majority view is that the principle of concurrent causation

applies to cases involving enhanced injuries and, as a result, the

principles of comparative fault apply.     See, e.g., Montag by Montag v.

Honda Motor Co., 75 F.3d 1414, 1419 (10th Cir. 1996); Gen. Motors Corp.

v. Farnsworth, 965 P.2d 1209, 1218 (Alaska 1998); Daly v. Gen. Motors

Corp., 575 P.2d 1162, 1169–70 (Cal. 1978); Estate of Hunter v. Gen.

Motors Corp., 729 So. 2d 1264, 1273–75 (Miss. 1999); Harsh v. Petroll,

887 A.2d 209, 218 (Pa. 2005); Duncan v. Cessna Aircraft Co., 665 S.W.2d

414, 428 (Tex. 1984).

         The majority view may be supported in part on the ground that it

imposes upon users the responsibility to safely use products and that it

would be unfair to impose costs of substandard plaintiff conduct on

manufacturers, who would presumably pass on some or all of those costs

to users and consumers, including those who use and consume products

safely and wisely.      See William J. McNichols, The Relevance of the

Plaintiff’s Misconduct in Strict Tort Products Liability, the Advent of
                                    8

Comparative Responsibility, and the Proposed Restatement (Third) of

Torts, 47 Okla. L. Rev. 201, 283–84 (1994).

      A minority of cases, however, do not apply comparative fault

principles or at least limit their application in the enhanced injury

context. See, e.g., Binakonsky v. Ford Motor Co., 133 F.3d 281, 288 (4th

Cir. 1998); D’Amario v. Ford Motor Co., 806 So. 2d 424, 426 (Fla. 2001);

Andrews v. Harley Davidson, Inc., 796 P.2d 1092, 1095 (Nev. 1990);

Green v. Gen. Motors Corp., 709 A.2d 205, 209 (N.J. Super. Ct. App. Div.

1998); Alami v. Volkswagen of Am., Inc., 766 N.E.2d 574, 575 (N.Y.

2002).     Some of these cases, however, arise in jurisdictions applying

contributory negligence and may have been motivated by a desire to

prevent the harsh result of completely denying a plaintiff recovery where

the plaintiff’s negligence was modest. See, e.g., Binakonsky, 133 F.3d at

284; Andrews, 796 P.2d at 1095; Restatement (Second) of Torts § 402A

cmt. n, at 356 (1965). The minority viewpoint has its adherents in the

academic literature.    See generally Robert C. Reichert, Limitations on

Manufacturer Liability in Second Collision Actions, 43 Mont. L. Rev. 109

(1982).

      The reasoning behind the minority line of cases is often that a

manufacturer has a duty to minimize the injurious effect of a crash no

matter how the crash is caused and has a duty to anticipate foreseeable

negligence of users and third parties.     As noted by the New Jersey

Supreme Court, “ ‘[o]nce it is established that the defendant has a duty

to protect persons from the consequences of their own foreseeable faulty

conduct, it makes no sense to deny recovery because of the nature of the

plaintiff’s conduct.’ ” Green v. Sterling Extruder Corp., 471 A.2d 15, 20

(N.J. 1984) (quoting Patricia Marschall, An Obvious Wrong Does Not Make

a Right:    Manufacturer’s Liability for Patently Dangerous Products, 48
                                      9

N.Y.U. L. Rev. 1065, 1088 (1973)).        This viewpoint was reiterated in

Jimenez, where the court observed that “the concept of ‘enhanced injury’

effectively apportions fault and damages on a comparative basis;

defendant is liable only for the increased injury caused by its own

conduct, not for the injury resulting from the crash itself.” Jimenez v.

Chrysler Corp., 74 F. Supp. 2d 548, 566 (D.S.C. 1999), rev’d in part and

vacated in part by Jimenez v. DaimlerChrysler Corp., 269 F.3d 439 (4th

Cir. 2001).   In addition, some cases support the minority rule on the

ground that product manufacturers should be encouraged to design

products that protect the user in the event of an accident. Andrews, 796

P.2d at 1095.

      C.   Restatement (Third) of Torts.         Against the above clash of

court cases and academic antlers, the American Law Institute in the

Restatement (Third) of Torts:     Products Liability considered the proper

approach to enhanced injury claims in sections 16 and 17.

      Section 16 of the Restatement (Third): Products Liability provides:
           (a) When a product is defective at the time of
      commercial sale or other distribution and the defect is a
      substantial factor in increasing the plaintiff’s harm beyond
      that which would have resulted from other causes, the
      product seller is subject to liability for the increased harm.
            (b) If proof supports a determination of the harm that
      would have resulted from other causes in the absence of the
      product defect, the product seller’s liability is limited to the
      increased harm attributable solely to the product defect.
              (c) If proof does not support a determination under
      Subsection (b) of the harm that would have resulted in the
      absence of the product defect, the product seller is liable for
      all of the plaintiff’s harm attributable to the defect and other
      causes.
              (d) A seller of a defective product that is held liable for
      part of the harm suffered by the plaintiff under Subsection
      (b), or all of the harm suffered by plaintiff under Subsection
      (c), is jointly and severally liable or severally liable with other
      parties who bear legal responsibility for causing the harm,
                                       10
      determined by the applicable rules of joint and several
      liability.
Restatement (Third) of Torts: Products Liability § 16, at 235–36 (1998).
Section 17 provides:
             (a) A plaintiff’s recovery of damages for harm caused
      by a product defect may be reduced if the conduct of the
      plaintiff combines with the product defect to cause the harm
      and the plaintiff’s conduct fails to conform to generally
      applicable rules establishing appropriate standards of care.
            (b) The manner and extent of the reduction under
      Subsection (a) and the apportionment of plaintiff’s recovery
      among multiple defendants are governed by generally
      applicable rules apportioning responsibility.
Id. § 17, at 256.

      With respect to the issue of indivisible harm in an enhanced injury

case, the language of section 16(c) supports the Fox-Mitchell approach.

This interpretation is confirmed by the Reporter’s Note to section 16,

which expressly states that the Fox-Mitchell approach is the majority

viewpoint and is embraced in the Restatement (Third). Id. § 16 reporter’s

note to cmt. d, at 244. The Reporter’s Note emphasizes, however, that

section 16(c) does not formally shift any burden of proof to the

defendant. Id. Instead, according to the Reporter’s Note,
      if the plaintiff has established that the product defect
      increased the harm over and above that which the plaintiff
      would have suffered had the product been nondefective, and
      if, at the close of the case, proof does not support a
      determination of the harm that would have resulted in the
      absence of the product defect, then the defendant is liable
      for all the harm suffered by the plaintiff.
Id.

      On the issue of application of comparative fault, the Restatement

(Third) section 17(b) indicates that generally applicable comparative fault

principles should apply among multiple defendants.                The official

comments     to     section   17,   however,   address   only   the   issue   of

apportionment of plaintiffs’ fault. The Reporter’s Note emphasizes that a
                                    11

majority of courts utilize comparative fault to reduce the recoveries of

product liability plaintiffs, but does not discuss the issue of applying

comparative fault principles among defendants. Id. § 17 reporter’s note

to cmt. a, at 259–60.

      D. Iowa Case Law on Enhanced Injury. We begin discussion of

Iowa law with a review of our prior approach to “indivisible injuries”—

where two or more separate negligent acts or omissions result in an

indivisible injury. In Meek v. Long, 258 Iowa 1309, 1314, 142 N.W.2d

385, 388–89 (1966), the court held that where the injuries to a plaintiff

resulting from two separate accidents were indivisible, the defendant

should not be permitted to benefit from the inability to attribute all

damages to one incident or the other.

      The holding of Meek was extended to situations involving separate

defendants in Treanor v. B.P.E. Leasing, Inc., 158 N.W.2d 4 (Iowa 1968).

In Treanor, the plaintiff sought to recover for personal injuries allegedly

suffered in two separate automobile accidents. Treanor, 158 N.W.2d at

5.   We held that to the extent there were indivisible damages, both

defendants would be jointly and severally liable for injuries which could

not with reasonable certainty be attributed solely to the other. Id. at 7.

      There are two Iowa Supreme Court cases subsequent to Meek and

Treanor that deal with the question of enhanced injuries arising out of a

single accident. In Hillrichs v. Avoc Corp., 478 N.W.2d 70, 71–72 (Iowa

1991), a farmer brought an action against a manufacturer and an

implement dealer after his hand was crushed in the husking bed of a

corn picker.   While being used to pick corn, the implement became

plugged with corn husks. Hillrichs, 478 N.W.2d at 71. Unable to unplug

the husking bed, the plaintiff reached into the equipment with a gloved

hand. Id. at 72. The glove on his right hand entangled in the rollers,
                                      12

trapping the plaintiff’s hand for approximately one-half hour and

resulting in significant injuries. Id. The plaintiff claimed that the corn

picker    was   unreasonably     dangerous    because:    (1) “it   lacked   an

interlocking shield over the rollers that would disengage the power

source when the shield was removed” and (2) “it lacked an emergency

shut-off device” that would be triggered when a foreign body became

entangled in the machine. Id.

        At trial, the plaintiff sought jury instructions and verdict forms

requiring the jury to apportion damages arising from the initial

entanglement in the machine from damages caused by the failure of the

machine to shut off power upon becoming entangled. Id. The trial court

declined to give the plaintiff’s requested instructions on apportionment.

Id.

        At first, the jury returned a verdict finding the plaintiff seventy

percent at fault, the manufacturer twenty-five percent at fault, and the

dealer five percent at fault. Id. The jury also found, however, that the

defendants’ fault was not a proximate cause of the plaintiff’s injuries. Id.

The trial court rejected the verdicts as inconsistent and directed the jury

to reconsider the issues consistent with the instructions. Id. The jury

then returned a verdict finding the plaintiff one hundred percent at fault.

Id.

        On appeal, this court held that the plaintiffs’ claim for “enhanced

injuries” against the manufacturer should have been submitted to the

jury.     Id. at 75.     The court, however, disagreed with plaintiffs’

apportionment theory. We stated:
              Although plaintiff suggests that any percentage of fault
        that might be assigned to him with respect to the initial
        entanglement in the machinery may not be assessed to him
        on the trial of his enhanced injury claim, we disagree with
        that contention. The fault of the plaintiff, if any, in becoming
                                     13
      entangled in the machinery would be a proximate cause of
      the enhanced injury as well as the initial injury.
Id. at 76. Although Hillrichs involved an enhanced injury case where the
defendant alleged comparative fault of the plaintiff, the rationale of the

case would seem to apply to cases where a defendant sought to compare

its fault with that of a codefendant or released party.

      Thirteen months later, this court decided Reed v. Chrysler Corp.,

494 N.W.2d 224 (Iowa 1992). In Reed, an injured passenger brought a

products liability action against an automobile manufacturer for injuries

arising from a one-vehicle accident.      Reed, 494 N.W.2d at 225.       An

intoxicated driver lost control of his vehicle, which ultimately slammed

into a concrete bridge abutment, rolled, and traveled three hundred feet

on the road upside down on its roll bar. Id. at 225–26. The plaintiff, a

backseat passenger, suffered severe injuries in the mishap. Id. at 226.

Like the driver, he was also intoxicated. Id.

      The plaintiff in Reed claimed that the vehicle had a defective

windshield and removable hardtop.         Id. at 227.     The district court

granted the defendant a directed verdict on the ground that the plaintiff

failed to present evidence of an alternative design, practicable under all

the circumstances. Id.

      We reversed the district court’s grant of a directed verdict. Id. As

a threshold matter, we held that the plaintiff had generated a jury

question on whether there was an alternative design that was practicable

under all the circumstances.      Id. at 227–28.     We then went on to

consider other elements of a crashworthiness claim.         Specifically, we

considered whether Reed presented sufficient evidence to show what

injuries would have resulted if the safer design method had been used.

Id. at 228. We held that Reed offered sufficient evidence to show that the
                                    14

injury to his arm would not have occurred if the vehicle had a more

safely-designed metal top. Id.

      We also addressed the question of the admissibility of the driver’s

and Reed’s intoxication. Id. at 229–30. We held that the evidence was

inadmissible. Id. at 230. We recognized that in Hillrichs we held that a

plaintiff’s comparative fault could be used against him in a claim for

enhanced injuries. Id. We, nevertheless, reconsidered Hillrichs and held

that a plaintiff’s comparative fault should not be so assessed in a

crashworthiness case unless it is shown to be a proximate cause of the

enhanced injury.    Id. (abrogating Hillrichs).   Because there was no

evidence that the driver’s or Reed’s intoxication had any bearing on how

Reed’s injuries were enhanced, the evidence of intoxication was

inadmissible. Id.

      The core rationale of the result in Reed was expressed as follows:
      The theory [of an enhanced injury claim], which presupposes
      the occurrence of accidents precipitated for myriad reasons,
      focuses alone on the enhancement of resulting injuries. The
      rule does not pretend that the design defect had anything to
      do with causing the accident. It is enough if the design
      defect increased the damages. So any participation by the
      plaintiff in bringing the accident about is quite beside the
      point.
Id. This rationale is consistent with the minority view that comparative

fault principles do not apply to claims of enhanced injury.

      The Reed decision drew a sharp dissent. Id. (Carter, J., concurring

in part and dissenting in part). The dissent argued that under Iowa’s

comparative fault framework, fault “resulting” in injuries was to be

compared with a strict liability defendant in an enhanced injury case. Id.

at 231.   Unlike the majority, the dissent argued that the plaintiff’s

negligence was a proximate cause of the enhanced injury and that the

conduct of the manufacturer was not an intervening cause in the case.
                                    15

Id.   The dissent asserted that the ordinary rules of proximate cause

should apply in enhanced injury cases and that, in the comparative fault

setting, any fault of the plaintiff or other person should be compared

against the fault of the manufacturer.       Id.   The dissent is a clear

articulation of the majority view which has prevailed in a number of

jurisdictions and which has been embraced in the Restatement (Third) of

Torts section 17(b).

       Neither Reed nor Hillrichs directly considered whether to follow the

approach of Hubbell or Fox-Mitchell on the question of indivisible injury.

The Reporter’s Note to the Restatement (Third) observed that the court in

Hillrichs stated, “ ‘Damages may be awarded . . . when the only dispute is

the amount of damages and the evidence affords a reasonable basis for

estimating the loss.’ ” Restatement (Third) § 16 reporter’s note to cmt. d,

at 251 (quoting Hillrichs, 478 N.W.2d at 75). But this limited statement

is true regardless of whether Hubbell or Fox-Mitchell is applicable. This

issue thus presents a question of first impression under Iowa law.

       In Iowa, however, the issue may have limited impact. In Reed, we

discussed how a party may prove apportionment. First, a plaintiff must

offer substantial evidence to prove, ordinarily through expert testimony,

that the alleged defect in fact caused an enhanced injury.            Once

substantial evidence on the fact of enhanced injury has been established,

the plaintiff is not required to prove the amount of injury with exactitude.

Reed, 494 N.W.2d at 228. Because of the relatively liberal approach to

establishing apportionment, the allocation of the burden of proof may not

be as problematic as it once seemed.

       E.   Adoption of Fox-Mitchell Approach to Causation and

Rejection of Divisible Injury Requirement. As stated in the Reporter’s

Note, the Restatement (Third) section 16(c) expressly adopts the Fox-
                                     16

Mitchell approach to indivisible harm.       Although Hubbell has a few

adherents, on this issue of first impression, we adopt the Fox-Mitchell

approach.    We believe the Fox-Mitchell approach to causation and the

rejection of a requirement that plaintiff show a divisible harm is the

soundest approach because it is the most consistent with our

established law regarding indivisible injuries of successive tortfeasors in

Meek and Treanor.

       Specifically, we hold that in an enhanced injury case, the plaintiff

has the burden of showing the fact of enhanced injury. This burden can

be met by offering evidence that the design defect was a substantial

cause of injury above and beyond that which would have occurred

without the design defect. There is no requirement that a plaintiff prove

a divisible injury. We regard the above statement of law as consistent

with Restatement (Third) of Torts: Products Liability section 16(b) and (c).

       F.   Application of Comparative Fault and Joint and Several

Liability in Iowa Code Chapter 668.           Reed plainly stands for the

proposition that comparative fault concepts of Iowa Code chapter 668 do

not apply in enhanced injury cases. Because Reed involved the potential

fault of the driver of the vehicle as well as the plaintiff, the holding in

Reed    applies   to   apportionment      among   defendants    as   well   to

apportionment between the plaintiff and the product manufacturer. The

question is thus whether Reed should be abandoned in favor of the

approach of the Restatement (Third).

       A central issue lurking behind this question is whether the

enhanced injury, or injury occurring because of the product defect in an

automobile, was proximately caused by the conduct of the initial

tortfeasor. In Hillrichs, we declared that the fault of the plaintiff, if any,

would be a proximate cause of the enhanced injury.             Hillrichs, 478
                                    17

N.W.2d at 76. By contrast, in Reed, we stated that the intoxication of the

driver or of Reed did not bear on the issue of how Reed’s injuries were

enhanced by the construction of the Jeep’s roof. Reed, 494 N.W.2d at

230.

       Under Iowa law, tortfeasors are responsible for the natural and

foreseeable consequences of their acts.    Virden v. Betts & Beer Constr.

Co., 656 N.W.2d 805, 808 (Iowa 2003). We have repeatedly held that the

tortious conduct of others can be natural and foreseeable in the context

of medical negligence which results after a plaintiff is injured. See Casey

v. Koos, 323 N.W.2d 193, 197 (Iowa 1982); Smith v. Conn, 163 N.W.2d

407, 410 (Iowa 1968). It is hard to see how a different approach should

apply to a case involving a product defect in an automobile. As noted by

the Alaska Supreme Court, “it is just as foreseeable to an original

tortfeasor that equipment in a car may malfunction as it is that a doctor

may act negligently in treating the plaintiff’s injuries.” Farnsworth, 965

P.2d at 1218; see also Harsh, 887 A.2d at 218 (“insulating a negligent

tortfeasor from liability for enhanced injuries based on his status as the

sole cause of some other distinct harm would engender substantial

incongruities in Pennsylvania law”).

       In addition, the question of whether fault should be apportioned in

enhanced injury cases is no longer solely a question of common law

development.    Instead, we must consider the provisions of Iowa Code

chapter 668, which codify comparative fault principles.      Unlike many

comparative fault statutes which apply comparative fault concepts only

in cases involving negligence, see, e.g., Melia v. Ford Motor Co., 534 F.2d

795, 802 (8th Cir. 1976) (applying Nebraska law); Kirkland v. Gen. Motors

Corp., 521 P.2d 1353, 1367 (Okla. 1974), Iowa’s comparative fault

statute expressly states that the fault of other parties is to be compared
                                      18

in cases of negligence, recklessness, and strict liability. Coker v. Abell-

Howe Co., 491 N.W.2d 143, 147 (Iowa 1992) (citing Iowa Code § 668.1

(1991)).   While an exception to the application of comparative fault

principles for enhanced injury cases might be supported on policy

grounds, the legislature has not provided for such an exception.        See

Montag, 75 F.3d at 1419 (noting broadly worded comparative fault act

applies to enhanced injury claims).

      Further, the legislature in Iowa Code section 668.3(3) has

expressly stated that “[i]n determining the percentages of fault, the trier

of fact shall consider both the nature of the conduct of each party and

the extent of the casual relation between the conduct and the damages

claimed.” In this language, we conclude that in enhanced injury cases,

the legislature has directed that the casual relation between the conduct

of a product manufacturer and the resulting damages is one of the two

elements to be considered in assigning a percentage of liability, but is not

solely determinative as to the allocation of fault.

      We recognize, however, that in cases where the factfinder has

found a divisible injury, the liability of the product manufacturer, though

subject to comparative fault analysis, is limited to the amount of the

divisible injury. Restatement (Third) § 16(b), at 236. Having found that

the comparative fault provisions of Iowa Code chapter 668 apply to

enhanced injury cases, it follows that the joint and several liability

provisions of Iowa Code section 668.4 apply to parties liable for divisible

or indivisible injuries.

      In light of the Restatement (Third), the evolving case law from other

jurisdictions, and our duty to interpret Iowa Code chapter 668 in

accordance with the legislative intent revealed by its language, we
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overrule Reed and align our law with the Restatement (Third) and the

majority of jurisdictions.

      III. Conclusion.

      We adopt the Fox-Mitchell approach to the required causation in

enhanced injury cases.        We further hold that the principles of

comparative fault and joint and several liability found in Iowa Code

chapter 668 apply in enhanced injury cases. As a result, the answer to

both certified questions is “Yes.”

      CERTIFIED QUESTIONS ANSWERED.
