                   FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

EVELYN ROSA and ROBERT ROSA, as          
individuals, and HOLLY ROSA, as
an individual and as the personal
representative of Michael Robert
Rosa, deceased,                                No. 09-17792
               Plaintiffs-Appellants,
                and                             D.C. No.
                                             5:05-cv-03577-JF
DAVID ROSA,                                      OPINION
                            Plaintiff,
                 v.
TASER INTERNATIONAL, INC.,
                Defendant-Appellee.
                                         
        Appeal from the United States District Court
           for the Northern District of California
         Jeremy D. Fogel, District Judge, Presiding

                   Argued and Submitted
         April 17, 2012—San Francisco, California

                      Filed July 10, 2012

 Before: Mary M. Schroeder, Diarmuid F. O’Scannlain, and
             Susan P. Graber, Circuit Judges.

                Opinion by Judge O’Scannlain




                              7943
7946             ROSA v. TASER INTERNATIONAL
                          COUNSEL

John Burton, The Law Offices of John Burton, Pasadena, Cal-
ifornia, argued the cause and filed the briefs for the individual
appellants, Evelyn and Robert Rosa and for appellant Holly
Rosa, as an individual and as the personal representative of
Michael Robert Rosa. With him on the briefs was Peter M.
Williamson, Williamson & Kraus, Woodland Hills, Califor-
nia.

John R. Maley, Barnes & Thornburg LLP, Indianapolis, Indi-
ana, argued the cause and filed the brief for appellee, TASER
International, Inc. With him on the brief was Mildred K.
O’Linn, Manning & Marder, Kass, Ellrod, Ramirez LLP, Los
Angeles, California.


                          OPINION

O’SCANNLAIN, Circuit Judge:

   We are called upon to decide whether, in August 2004, a
manufacturer of electronic control devices, commonly
referred to as “tasers,” was under a duty to warn that repeated
exposure to its products could lead to fatal levels of metabolic
acidosis.

                                I

   Shortly after 11:00 p.m. on August 29, 2004, a resident of
Del Rey Oaks, California, called the police to report that
someone who “look[ed] pretty disturbed” was “walking up
and down the street yelling ‘Mario’ and . . . some other stuff.”
Del Rey Oaks Police Officer Russell Van Zanten responded
to this noise complaint and found Michael Rosa (“Michael”)
still in the street. Believing that Michael was “either really
high or crazy,” Van Zanten approached him with considerable
                    ROSA v. TASER INTERNATIONAL                        7947
caution. Without fully exiting his patrol vehicle, Van Zanten
identified himself as a police officer. Michael circled the
vehicle—striking the hood with his hand as he passed—and
began staggering down the street. Van Zanten followed in his
vehicle, calling for assistance from surrounding law enforce-
ment agencies.

   Officer Jack Jeffrey Powell was the first of at least six addi-
tional officers to arrive. Due to Powell’s angle of approach,
Michael found himself between two patrol cars facing each
other. At this point, he started “moving really awkwardly,
kind of just like freaking out.” The situation deteriorated rap-
idly as more officers arrived and as Michael attempted to flee,
breaking at least one fence in the process.

   The pursuit ended when Michael jumped over a three-foot
fence, assumed a batter’s stance, and began swinging a piece
of two-by-four. Unable to convince Michael to comply with
verbal commands and concerned for his safety, Officer Mat-
thew Doza deployed his ADVANCED TASER M26 ECD
(“M26”)—a weapon known as an electronic control device
that is manufactured by defendant-appellee TASER Interna-
tional, Inc. (“TASER”1)—in “probe mode.”2 Michael then
tumbled down an embankment, breaking the leads and ending
the shock. Officer Doza followed, loading a new cartridge as
he went. When Michael appeared to be reaching for the two-
by-four again, Officer Doza redeployed his M26. Michael was
apparently not incapacitated by this deployment. But, noting
some effect on him, Doza depressed the trigger an additional
   1
     Incidentally, TASER is an acronym for “Thomas A. Swift’s Electric
Rifle.” See Jeffrey D. Ho, et al., Absence of Electrocardiographic Change
After Prolonged Application of a Conducted Electrical Weapon in Physi-
cally Exhausted Adults, 41 J. EMERGENCY MED. 466, 469 (2009)
   2
     Deployed thus, two metal darts shoot out of the front of the M26 and
lodge in the target’s body. If it is functioning properly, the M26 will emit
a series of electrical pulses over a cycle of five seconds that will override
the target’s central nervous system, cause involuntary muscle contractions,
and prevent him from continuing to attack officers.
7948                ROSA v. TASER INTERNATIONAL
six or seven times. Seeing that Michael continued to struggle,
newly arrived Officer Nicholas Borges deployed his own
M26. He cycled his M26 three times before Michael finally
hit the ground.

   Nevertheless, Michael continued to resist as yet another
officer, Katie Reyes, attempted to place him in handcuffs.
Including Officer Reyes, it took the efforts of six officers to
subdue him. And in order finally to take him into custody,
Doza once again had to apply his M26, this time in “drive-
stun mode” to Michael’s upper leg.3 Until the handcuffs were
in place, Michael continued to struggle and did not appear to
be in medical distress.

   After officers had Michael in restraints, they rolled him
onto his side. At this point, Michael slumped, his lips blue, his
breathing erratic. He quickly stopped breathing entirely. Offi-
cers were unable to find a pulse and immediately began resus-
citation efforts. Michael was transported to the hospital,
where resuscitation efforts continued. But Michael’s heart
went into atrial arrhythmia (a form of irregular heartbeat),
tachycardia (accelerated heartbeat), and finally asystole (car-
diac arrest). He was pronounced dead at about 12:30 a.m. on
August 30, 2004.

   Dr. John Hain performed the autopsy. Discovering high
levels of methamphetamine in Michael’s blood, Dr. Hain con-
cluded that his cause of death was “ventricular arrhythmia . . .
due to methamphetamine intoxication.” He listed “Taser
application and arrest by police” as contributing conditions.
Michael’s death was subsequently linked to metabolic acido-
sis, a condition under which lactic acid—a byproduct of phys-
ical exertion—accumulates more quickly than the body can
  3
    Deployed in this manner, two electrodes in the front of the M26 are
placed in direct contact with the target’s skin. This method also uses a
series of electrical pulses over a period of five seconds, but it functions by
inducing pain rather than involuntary muscle contractions.
                   ROSA v. TASER INTERNATIONAL                      7949
dispose of it, causing the pH in the body to decrease. The con-
dition makes sudden cardiac arrest more likely.

    Plaintiffs-appellants, Michael’s parents, Evelyn and Robert,
and his daughter Holly (collectively “Rosas”) brought this
lawsuit against TASER, as manufacturer of the M26, assert-
ing that Michael died because it had provided an inadequate
warning of the dangers of the product to the officers who used
it.4 They pursued both strict liability and negligence theories
under California law based upon this failure to warn. At the
times in question, TASER provided warnings that read in rel-
evant part:

      While the medical evidence strongly supports the
      [M26] will not cause lasting effects or fatality, it is
      important to remember the very nature of physical
      confrontation involves a degree of risk that someone
      will get hurt or may even be killed due to unforeseen
      circumstances and individual susceptibilities.
      Accordingly, the [M26] should be treated as a seri-
      ous weapon and should only be deployed in situa-
      tions where the alternative would be to use other
      force measures which carry similar or higher degrees
      of risk.

The Rosas claimed that TASER also should have warned that
repeated exposure to the M26 carried its own risks, particu-
larly the risk that it can cause fatal levels of metabolic acido-
sis.

   After the conclusion of discovery, the district court
awarded summary judgment to the defendant. The court con-
cluded that the Rosas had not established a triable issue of
fact that the risk of metabolic acidosis was known or know-
  4
    The Rosas, initially including Michael’s brother David, also sued the
officers and municipalities involved, but those claims are not at issue in
this appeal.
7950               ROSA v. TASER INTERNATIONAL
able when the M26 at issue was distributed in December 2003
(or even when Michael died the following August). Rosa v.
City of Seaside, 675 F. Supp. 2d 1006, 1013-14 (N.D. Cal.
2009) (order). It reasoned that the scientific research cited by
the Rosas did not address TASER’s products, was not pub-
licly available, or represented nothing more than hypotheses,
unproven by scientific methodology. Id. As a result, it con-
cluded that the manufacturer was not liable under strict liabil-
ity. Id. at 1014. The district court concluded based on similar
flaws of proof that the Rosas had not established a triable
issue of fact that TASER should have known of the risk.
Thus, it was not liable for negligence. Id. at 1015. The Rosas
timely appealed.

                                    II

   The Rosas first argue that the district court construed
TASER’s duty to warn too narrowly under California’s strict
liability rules.5 They assert that TASER had a broader duty to
test the risks of its products, as well as to integrate into its
warnings information gleaned from isolated reports of poten-
tial side effects.

                                    A

   [1] California law places a duty on manufacturers to warn
of a “particular risk” if it is “known or knowable in light of
the generally recognized and prevailing best scientific and
medical knowledge available at the time of manufacture and
distribution.” Conte v. Wyeth, Inc., 85 Cal. Rptr. 3d 299, 310
  5
    The Rosas argue that Heston v. Salinas, 431 F. App’x 586 (9th Cir.
2011) (unpublished) has some preclusive effect on this case. The district
court was aware of Heston and noted that it concerned a different period
of time. Rosa, 675 F. Supp. 2d at 1015. The Rosas, as the parties raising
preclusion, bear the burden of establishing an identity of issues, but they
have failed to do so. See United States v. Lasky, 600 F.2d 765, 769 (9th
Cir. 1979). Because the identity of issues between this case and Heston is
not established, the Rosas’ preclusion argument fails.
                 ROSA v. TASER INTERNATIONAL                7951
(Ct. App. 2008) (emphasis added). Thus, this case turns on
what was “knowable” by a manufacturer of electronic control
devices in December 2003. The Rosas argue essentially that
any risk that was discoverable through modern technology, no
matter how unsubstantiated, was knowable by TASER. We do
not interpret the standard so broadly.

   [2] Though the California courts have never announced a
comprehensive standard of when a particular risk is “know-
able,” a few key considerations are clear. “[A] manufacturer
is held to the knowledge and skill of an expert in the field; it
is obliged to keep abreast of any scientific discoveries and is
presumed to know the results of all such advances.” Carlin v.
Superior Court, 920 P.2d 1347, 1351 n.3 (Cal. 1996). A man-
ufacturer cannot defeat liability because it did not review the
relevant scientific literature.

   [3] But a manufacturer is not under a duty to warn of
“every report of a possible risk, no matter how speculative,
conjectural, or tentative,” because “inundat[ing the public]
indiscriminately with notice of any and every hint of danger”
would “inevitably dilut[e] the force of any specific warning
given.” Finn v. G.D. Searle & Co., 677 P.2d 1147, 1153 (Cal.
1984); see also Brown v. Superior Ct., 751 P.2d 470, 480-81
(Cal. 1988) (noting that strict liability is not designed to turn
manufacturers into insurers of their product). For example, in
Finn v. G.D. Searle & Co., doctors prescribed diodoquin to a
child diagnosed in 1969 with acrodermatitis enteropathica
after experiencing a severe rash and diarrhea. In 1971, the
child developed vision problems caused by optic nerve atro-
phy. His parents sued the manufacturer of diodoquin for a
failure to warn. To show that the risk that diodoquin could
cause optic nerve atrophy was knowable at the time of distri-
bution, the Finns presented a 1966 article published in the
British medical journal, The Lancet, reporting another case of
a child developing optic nerve atrophy after long term use of
diodoquin for the same condition. 677 P.2d at 1149-50. They
also presented a 1971 report implicating a drug in the same
7952            ROSA v. TASER INTERNATIONAL
chemical family in causing optic nerve atrophy. Id. In that
case, the defendants were not held liable for failure to warn,
and the California Supreme Court clarified that “[k]nowledge
of a potential side effect which is based on a single isolated
report of a possible link between a [product] and an injury
may not require a warning.” Id. at 1153. That is, such reports
of isolated or speculative injuries do not constitute generally
accepted medical knowledge.

                               B

                               1

  To establish that the risk that TASER’s products could
cause fatal levels of metabolic acidosis was knowable by
December 2003, the Rosas rely primarily on four peer-
reviewed articles. We conclude that these articles do not pre-
sent a triable issue of fact that the risk was more than purely
speculative.

   [4] First, the Rosas point to a 1966 study of the impact of
acidosis on the risk of ventricular fibrillation (a form of car-
diac arrhythmia). See Paul H. Gerst, et al., Increased Suscepti-
bility of the Heart to Ventricular Fibrillation During
Metabolic Acidosis, 19 CIRCULATION RESEARCH 63 (1966).
This study demonstrates nothing more than that the risk of
ventricular fibrillation increases as blood pH decreases. Id. at
63. But the study makes no attempt to link either its findings
or acidosis to the use of electronic control devices. Further-
more, the authors themselves warn that “it may not be justifi-
able to extrapolate conclusions derived from an experimental
study such as this to human physiology.” Id. at 68. Given
these limitations, this article did not place TASER on notice
that its products could cause cardiac problems in humans.

  [5] Second, the Rosas point to a 1999 case study examin-
ing the link between metabolic acidosis and deaths that occur
while in police custody. See John L. Hick, et al., Metabolic
                ROSA v. TASER INTERNATIONAL               7953
Acidosis in Restraint-Associated Cardiac Arrest: A Case
Series, 6 ACAD. EMERGENCY MED. 239 (1999). This study was
one of a number performed to determine the causes of a phe-
nomenon known as “sudden in-custody death syndrome.” Id.
at 243. As the study pointed out, “[t]he phenomenon of sud-
den death in restraints has long been recognized,” but “[t]he
physiologic derangements that lead to death are still poorly
understood.” Id. at 241. Proposed hypotheses included “auto-
nomic reflexes, arrhythmias, or restraint stress” as well as
positional asphyxia, “cocaine ingestion[,] and significant
exertion.” Id. This study sought to examine the link between
acidosis and these deaths. The authors’ main thesis was that
prolonged struggle with police increases the risk of death by
causing acidosis; their only conclusion was that police should
eschew the “hobble restraint position” in favor of placing sus-
pects on their sides. Id. at 242. Not only was the study incom-
plete because “[l]actate levels,” an indicator of acidosis,
“were obtained in only one” of the five cases studied, but
none of the cases involved electronic control devices. Id. at
240. As the M26 was designed specifically to prevent the sort
of prolonged struggle that the article posed as the main risk
for acidosis, this article did not put TASER on notice that its
product might cause similar injuries.

   Third, the Rosas point to an article published in The Lancet
in 2001, which they claim provides the missing link between
electronic control devices and metabolic acidosis and thus to
cardiac arrhythmia. See Raymond Fish & Leslie A. Geddes,
Effects of Stun Guns and Tasers, 358 THE LANCET 687 (2001).
Finding the answers posed by previous attempts to explain
sudden in-custody death syndrome unsatisfying, Drs. Fish and
Geddes hypothesized that electronic control devices may con-
tribute to the condition by “affect[ing] acid-base balance” of
the individuals exposed to them. Id. at 688. However, they
made no attempt to test the hypothesis and noted that there
was “no adequate information” to link these deaths to expo-
sure to TASER’s products. This sort of hypothetical side
7954               ROSA v. TASER INTERNATIONAL
effect is insufficient to require a warning under California
law. Finn, 677 P.2d at 1153.

   Fourth, the Rosas point to a study that was performed on
behalf of the Department of Defense in 1999, but that did not
become publicly available until after Michael’s death. JOHN
M. KENNY, ET AL., HUMAN EFFECTS ADVISORY PANEL, REPORT OF
FINDINGS STICKY SHOCKER ASSESSMENT (1999). Assuming that
a document that is not publicly available can constitute gener-
ally accepted medical knowledge—which we doubt—this
study suffers the same problem as the article from The Lancet.
It merely states that “deaths following Taser[ ] use may be
due to acidosis.” Id. at 31. It does not purport to establish that
causal link and explicitly limits the reach of its findings due
to its small data set. Id. at 32.

   [6] Because these last two articles provided the only link
between electronic control devices and severe levels of acido-
sis, even taken with the Gerst and Hick studies, they do not
establish a triable issue of fact that the risk of metabolic aci-
dosis was knowable at the time of distribution.

                                    2

   [7] The Rosas attempt to avoid this outcome by pointing to
a warning TASER issued in 2009 that explicitly discusses the
risk of metabolic acidosis.6 In examining whether summary
judgment is appropriate, we “consider only alleged facts that
  6
    In relevant part, that warning reads: “The ECD can produce physio-
logic or metabolic effects which include, but are not limited to, changes
in acidosis. . . . Reasonable efforts should be made to minimize the num-
ber of ECD exposures and resulting physiologic and metabolic effects.” It
continues by warning law enforcement officers to pay special attention to
“physiologically or metabolically compromised” suspects, including those
with cardiac disease and the effects of drugs in their systems. These indi-
viduals, TASER warns, “may already be at risk of death or serious injury
. . . [;] any physiologic or metabolic change may cause or contribute to
death or serious injury.”
                    ROSA v. TASER INTERNATIONAL                        7955
would be admissible in evidence.” Filco v. Amana Refrigera-
tion, Inc., 709 F.2d 1257, 1260 (9th Cir. 1983) (citing FED. R.
CIV. P. 56(e)). Because the fact of this 2009 warning is not
admissible to establish what was knowable in December
2003, it cannot aid the Rosas in avoiding summary judgment.
FED. R. EVID. 407; see also Gauthier v. AMF, Inc., 788 F.2d
634, 636 (9th Cir. 1986) (applying Rule 407 in a products lia-
bility case under Montana law); Flaminio v. Honda Motor
Co., 733 F.2d 463, 471 (7th Cir. 1984) (explaining that Rule
407 was sufficiently procedural in nature to apply in diversity
cases under Erie R.R. Co. v. Tompkins, 304 U.S. 64 (1938)).7

                                    III

   [8] The Rosas next assert that the district court erred in
awarding summary judgment to TASER on their negligence
claim. Though they do not precisely lay out how their negli-
gence claim differs from their strict liability claim, they point
to repeated statements by the California courts that the duties
to warn under strict liability and negligence theories are not
coterminous. See, e.g., Valentine v. Baxter Healthcare Corp.,
81 Cal. Rptr. 2d 252, 263 (Ct. App. 1999). While this is true,
there is also considerable overlap between the two torts.
Indeed, generally a “manufacturer’s duty, per strict liability
. . . to warn of potential risks and side effects envelopes a
broader set of risk factors than the duty, per negligence . . .
to warn of facts which make the product ‘likely to be danger-
ous’ for its intended use.” Id. (emphasis in original). In this
  7
    Concluding that the risk of metabolic acidosis was not knowable in
2003 precludes the Rosas’ claim for punitive damages. To recover such
damages under California Civil Code § 3294, the Rosas must demonstrate
that “defendant acted with knowledge of the probable dangerous conse-
quences to plaintiff ’s interests and deliberately failed to avoid these con-
sequences.” Gawara v. U.S. Brass Corp., 74 Cal. Rptr. 2d 663, 674 (Ct.
App. 1998) (stating that proof of negligence is insufficient) (internal quo-
tation marks omitted). Logically, TASER could not have disregarded a
known risk that its products could cause fatal levels of metabolic acidosis
if at the time that risk was not knowable.
7956               ROSA v. TASER INTERNATIONAL
case, we see three potential circumstances when negligence
might provide a broader duty to warn than does strict liability,
but we conclude that the Rosas have not established a triable
issue of fact on any of them.

   First, under certain circumstances, California’s negligence
law may impose on a manufacturer a duty to warn individuals
who, while not users of its products, could foreseeably rely on
its warnings. For example, when the user of a generic pharma-
ceutical sues the manufacturer of the brand name medication
for the warning included in the Physician’s Desk Reference,
the user cannot recover under strict liability because he or she
was not injured by the manufacturer’s own products. Conte,
85 Cal. Rptr. 3d at 309-10, 316. However, because the brand
name manufacturers are responsible for disseminating the
information in the Physician’s Desk Reference, which others
would foreseeably rely upon, they may be held liable under
negligence. Id. at 317-18. Such a duty thus arises only in nar-
row circumstances that are not present here.

   Second, though California law measures the strict liability
duty to warn from the time a product was distributed, a manu-
facturer may be liable under negligence for failure to warn of
a risk that was subsequently discovered. Oxford v. Foster
Wheeler LLC, 99 Cal. Rptr. 3d 418, 432-33 (Ct. App. 2009)
(discussing Hernandez v. Badger Constr. Equip. Co., 34 Cal.
Rptr. 2d 732 (Ct. App. 1994)). However, the record indicates
only one development between the date that this M26 was dis-
tributed and Michael’s death: TASER became aware of the
study regarding the “Sticky Shocker” done for the Department
of Defense.8 As discussed above, that study merely states an
  8
    The parties conceded at oral argument that the study that most strongly
supported Rosa’s position, James R. Jauchem, et al., Acidosis, Lactate,
Electrolytes, Muscle Enzymes, and Other Factors in the Blood of Sus
Scrofa Following Repeated TASER Exposures, 161 FORENSIC SCI. INT’L 20,
28 (2006), was first presented at a conference in late 2004, several months
after Michael’s death. It was not published for an additional two years.
                    ROSA v. TASER INTERNATIONAL                        7957
untested hypothesis. This does not create a triable issue of fact
that a reasonable manufacturer would have sent a supplemen-
tal warning based on this information.

   Third, under California law, TASER may be liable in negli-
gence for failure to undertake sufficient testing before distri-
bution. Cf. Valentine, 84 Cal. Rptr. 2d at 264. But the Rosas
have put forth no evidence creating an issue of fact regarding
whether it conducted reasonable testing. Before Michael’s
death, the perceived cardiac risk associated with the device
was immediate ventricular fibrillation, and TASER expended
considerable resources testing its products for that risk.9 This
does not establish a triable issue of fact that TASER failed to
exercise due care when this new risk was brought to its atten-
tion.

   [9] Because California law would not extend negligence
liability to a manufacturer in this circumstance, the district
court properly awarded summary judgment.

                                    IV

   [10] For the foregoing reasons, we conclude that the dis-
trict court properly awarded summary judgment in favor of
TASER because the risk of lactic acidosis was not knowable
in 2003. Thus, we do not reach TASER’s alternative argu-
ments.

   AFFIRMED.



   9
     When the perceived risk shifted to acidosis, TASER’s focus also
shifted, and its scientists published articles almost concurrently with those
upon which the Rosas rely. Compare James R. Jauchem, et al., supra note
8, at 7956, with Jeffrey D. Ho., et al., Cardiovascular and Physiologic
Effects of Conducted Electrical Weapon Discharge in Resting Adults, 13
ACAD. EMERGENCY MED. 1 (2006).
