                                                                   This opinion was

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                                                                    filed for record
                                                                 at^&fliori 3-A\       ^

     :OOUm;8WrEOFWASH(NQTOM

   DATE
   i            2 ]                                                Susan L. Carlson
                                                                 Supreme Court Clerk

      GtUBPJUSriCB



          IN THE SUPREME COURT OF THE STATE OF WASHINGTON




  L.M., a minor, by and through his Guardian             NO. 95173-0
  ad Litem WILLIAM L.E. DUSSAULT,

                        Petitioner,
                                                         EN BANC
          V.


  LAURA HAMILTON,individually and her
  marital community; LAURA HAMILTON                      Filed     MAR 2 I 2019
  LICENSED MIDWIFE, a Washington
  business.

                        Respondents.



        GORDON McCLOUD, J.—L.M. suffered a severe injury during birth and

 subsequently sued Laura Hamilton, the midwife who delivered him, for negligence.

 Hamilton prevailed at trial. L.M. now argues that the trial court erred by admitting

 evidence that natural forces of labor could have caused the injury and testimony from a

 biomechanical engineer to the same effect. L.M. argues that the trial court should have

 excluded the evidence under Frye^ and the testimony under ER 702.^




       'Frye v. United States, 54 App. D.C. 46, 293 F. 1013 (1923).

        ^ ER 702 provides: "If scientific, technical, or other specialized knowledge will
 assist the trier of fact to understand the evidence or to determine a fact in issue, a witness
 qualified as an expert by knowledge, skill, experience, training, or education, may testify
 thereto in the form of an opinion or otherwise."
L.M. V. Hamilton, No. 95173-0


       We affirm. Under Frye, the trial court must exclude evidence that is not based on

generally accepted science. Anderson v. Akzo Nobel Coatings, Inc., Ill Wn.2d 593, 603,

260 P.3d 857 (2011). And under ER 702, the trial court must exclude testimony from

unqualified experts and testimony that is unhelpful to the jury. Lakey v. Puget Sound

Energy, Inc., 176 Wn.2d 909, 918, 296 P.3d 860 (2013). Testimony is unhelpful to the

jury if it is unreliable, id., or lacks an adequate foundation,Johnston-Forbes v. Matsunaga,

181 Wn.2d 346, 357, 333 P.3d 388 (2014).

       L.M.'s Frye challenge concerns the extent to which the challenged science must be

generally accepted. And his ER 702 challenge hinges on the amount of discretion an

appellate court grants a trial court under that rule. But before we resolve either issue, we

must explore the current state ofthe challenged science because we review Frye challenges

de novo. We must also detail what the trial court did because we review ER 702 challenges

for abuse of discretion.


                       Factual and Procedural Background


   1. L.M. was injured during birth and subsequently sued the delivering midwife

       On April 4, 2010, Laura Hamilton, a midwife, delivered L.M. Ex. 2 (medical

records) at 7; see also Clerk's Papers (CP) at 1586. Her notes from the procedure show

that she performed an "assisted shoulder delivery" and that L.M.'s right arm was "weak at

side." Ex. 2 at 7; see also CP at 1586-87.

       In his first few months of life, L.M. experienced "complete paralysis" of his upper

arm, along with wealoiess of the entire arm. CP at 1567. In August 2010, exploratory

surgery to address the problem revealed substantial injuries to L.M.'s brachial plexus. Id.
L.M. V. Hamilton, No. 95173-0


The brachial plexus delivers signals from the spinal cord to the arm through a network of

nerves. CP at 1569. These nerves can suffer various injuries, the most severe of which are

avulsions(where the nerve is torn away from the spinal cord) and ruptures(where the nerve

is ripped apart). Id. Although most brachial plexus injuries (BPls) heal in six months,

avulsions and ruptures are permanent. CP at 1570; Verbatim Report ofProceedings(VRP)

(Oct. 28, 2015) at 27-28 (Test, of Robert DeMott, MD).

      L.M.'s BPI is most likely permanent. CP at 1568, 1590. All five of his brachial

nerve roots were injured: two were ruptured, one was avulsed, and two were partially

avulsed. CP at 1587. To this day, he has limited use of his arm and experiences pain. CP

at 1665-68, 1671.

       L.M., through his guardian ad litem, sued Hamilton. CP at 1453-58, 1395-1401.

He alleged that Hamilton responded negligently to his shoulder dystocia, an emergency in

which a baby's shoulder gets stuck during labor. CP at 1556-57, 1573, 1587-90. L.M.

claimed that Hamilton used excessive force, or traction, in her effort to free the shoulder.

Id. He claimed that only excessive traction—and not natural forces of labor (NFOL)—

could have caused his ruptures and avulsions. Id.

       Hamilton argued that she properly delivered L.M. and that NFOL can and did cause

L.M.'s BPI. CP at 1848, 2652-53, 2660, 2663-65. She argued that L.M. did not experience

shoulder dystocia. VRP (Oct. 23, 2015) at 16 (Test, of Laura Hamilton). To support her

defense, Hamilton offered the testimony of several experts, including Dr. Allan Tencer, a

biomechanical engineer. CP at 1518-24.
L.M. V. Hamilton, No. 95173-0


   2. The trial court denied L.M.'s motion to exclude NFOL evidence


          A. L.M. moved to exclude NFOL evidence


       Before trial, L.M. moved to exclude evidence of the NFOL theory as not generally

accepted under Frye and not helpful to the trier of fact under ER 702. CP at 1459-60.

According to L.M.,the relevant scientific community does not generally accept that NFOL

can cause "permanent, severe brachial plexus nerve avulsion and rupture," CP at 1482

(boldface omitted), and any suggestion to the contrary is too speculative to be admissible,

CP at 1473. L.M. drew support for his argument from two recent New York cases

excluding NFOL evidence. CP at 1475-79 (citing Muhammad v. Fitzpatrick, 91 A.D.3d

1353, 937 N.Y.S.2d 519 (App. Div. 2012); Nobre ex rel. Ferraro v. Shanahan, 42 Misc.

3d 909, 976 N.Y.S.2d 841 (Sup. Ct. 2013)).

       He also relied on deposition testimony or declarations from three experts. Dr.

Howard Mandel, an obstetrician-gynecologist, stated that "an avulsion or rupture of

brachial plexus nerve roots to an otherwise normal baby cannot occur from mere uterine

contractions or maternal pushing, the so-called 'forces of nature,' and there are no medical

studies or case reports to support that contention." CP at 1590; see also CP at 1510("You

can't get avulsion from stretch. It's just physiologically impossible.").^ Dr. Mandel


       ^ Dr. Mandel cited a publication in which Dr. Michael S. Kreitzer argues that'"there
is no direct evidence to support the assumption that [NFOL] can cause permanent injury
due to rupture or avulsion.'" CP at 1590-91 (quoting JAMES A. O'Leary, Shoulder
Dystocia and Birth Injury Prevention and Treatment 202(3d ed. 2010)); see also
CP at 1516-17 (making same argument in a letter to an editor). At trial, however. Dr.
Mandel conceded that NFOL can cause permanent BPIs. VRP (Oct. 21,2015)at 119(Test,
of Howard Mandel, MD)("I believe . . . you can have stretch from [NFOL]," and "[i]f you
have a bad stretch injury, the nerves can be permanently damaged.").
                                             4
L.M. V. Hamilton, No. 95173-0


acknowledged that he had not "done any research on nerve avulsion or specific reading on

it in over ten years." CP at 1511. Instead, he relied on his "education, training, and

experience and all the reading [he had] ever done." Id.

       Dr. Stephen Glass, a pediatric neurologist, stated that "[gjiven the character of

delivery and given the degree and extent of this severe plexus injury, it is improbable that

the 'natural forces' of labor and delivery were solely responsible." CP at 1567-68. He also

stated that "avulsion injuries are caused only by application of excessive manual traction

of the delivering provider while trying to alleviate the shoulder dystocia." CP at 1573. He

concluded, "There are no meaningful scientific studies that have measured the forces

necessary to cause a brachial plexus injury compared with the forces exerted by a laboring

mother." Id.'^

       And Pamela Kelly, a certified midwife, said that in her 30 years of practice, she had

"never heard of nor read any medical literature that says avulsion and ruptures of the

brachial plexus nerve roots ofan otherwise normal newborn can occur by way ofthe natural

forces of nature." CP at 1557 (boldface omitted).

              B. Hamilton opposed L.M.'s motion

       Hamilton argued that the NFOL theory "is based on generally accepted scientific

methodologies, principles, and techniques that have been published in the medical and

scientific literature over the last 25 years." CP at 1737. She relied heavily on a survey of


       ^ At trial. Dr. Glass conceded that NFOL "probably can contribute to some plexus
injuries." VRP (Oct. 22, 2015) at 89 (Test, of Stephen Glass, MD). Dr. Glass also
acknowledged that the literature includes case reports of NFOL causing permanent BPIs.
Id. at 115.
L.M. V. Hamilton, No. 95173-0


the medical literature by Dr. Robert DeMott, an obstetrician-gynecologist. CP at 1738-50,

1839-49. That literature shows that NFOL can clearly cause BPI, but it does not describe

what types of BPI—avulsion, rupture, etc.—this includes. CP at 1842-43. The reason is

that the precise subcategory of permanent BPI can be determined only by surgical

intervention, and "not all children with permanent injury undergo surgery where the

diagnosis of which type is able to be made." CP at 1839; see also CP at 1842-43. Dr.

DeMott disagreed with L.M.'s framing of the issue as whether the current literature shows

that NFOL cause avulsions or ruptures; Dr. DeMott believed the issue should be framed as

whether the current literature shows that NFOL cause permanent injuries. CP at 1842-43.

      In surveying the literature. Dr. DeMott discussed Williams Obstetrics,^ "one of the

preeminent textbooks on obstetrics." CP at 1839-40. He explained that the book reveals

the "evolution of the science" regarding NFOL and BPIs. CP at 1839. Although earlier

editions of the textbook suggest that BPIs usually result from excessive traction, newer

editions recognize that BPIs may also result from NFOL. CP at 1839, 1990, 1993. The

newest edition (at the time of trial) notes that "severe" BPIs "may also occur without . . .

shoulder dystocia." CP at 1999.




      ^ F. Gary Cunningham et al., Williams Obstetrics (21st ed. 2001); F. Gary
Cunningham et al., Williams Obstetrics(22d ed. 2005); F. Gary Cunningham et
AL., Williams Obstetrics (23d ed. 2010); F. Gary Cunningham et al., Williams
Obstetrics (24th ed. 2014).
L.M. V. Hamilton, No. 95173-0


       Dr. DeMott also discussed the fourth edition of PRECIS: An Update to Obstetrics

& Gynecology: Obstetrics.^ CP at 1840-41. That book claims that older textbooks state,

"without evidence," that BPIs are caused by excessive traction "in the presence of shoulder

dystocia." CP at 2006. But "multiple lines of evidence" now suggest that most BPIs are

caused by something else. Id. The book notes that more than half of BPIs occur in

uncomplicated vaginal deliveries and "mathematic and computer-simulated models"

suggest that NFOL are "far greater" than clinician-applied traction. Id.

       Dr. DeMott also referenced several other pieces of literature suggesting that NFOL

can cause permanent BPIs. See CP at 1843-49. For example, he cited a 2008 case report

published in the American Journal of Obstetrics & GynecologyJ CP at 1843, 2008-10.

That case report involved a mother who delivered a baby with one push and without

physician traction—"the only role the doctor played was to catch the baby before it went

off the table"—yet the baby suffered a permanent BPI. CP at 2009-10.

       Finally, Dr. DeMott discussed a 2014 "comprehensive, retrospective" report from

the American College Of Obstetrics and Gynecologists(ACOG)titled Neonatal Brachial

Plexus Palsy (ACOG Report or Report).^ CP at 1841, 1867-1976. That report reflects



      ^ Am. Coll. of Obstetricians & Gynecologists, PRECIS: An Update in
Obstetrics & Gynecology: Obstetrics (4th ed. 2013).

     'Henry Lerner, MD & Eva Salamon, MD, Permanent Brachial Plexus Injury
Following Vaginal Delivery without Physician Traction or Shoulder Dystocia, Am. J. of
Obstetrics & Gynecology, Mar. 2008, at e7-8.

      ^ Am. Coll. of Obstetricians & Gynecologists Task Force, Neonatal
Brachial Plexus Palsy (2014).
                                            7
L.M. V. Hamilton, No. 95173-0


ACOG's review of published literature, ineluding original research, review articles, and

commentaries. CP at 1876. The underlying literature was reviewed for quality. Id. The

AGOG Report states.

               The task force recognizes that knowledge about NBPP [neonatal
        brachial plexus palsy or BPI] is continually evolving. What is known at this
        time with reasonable medical certainty is that NBPP occurs infrequently and
        can be caused by maternal (endogenous) forces or clinician-applied
        (exogenous) forces or a combination of both. Similarly, NBPP can occur
        with or without associated, clinically recognizable shoulder dystocia.
        Finally, in the presence of shoulder dystocia, all intervention by way of
        ancillary maneuvers—no matter how expertly performed—will necessarily
        increase strain on the brachial plexus.

CP at 1882. The Report also shows that NFOL can cause permanent BPIs, noting that

injuries have "been shown to occur entirely unrelated to traction, with studies

demonstrating cases of both transient and persistent NBPP in fetuses delivered vaginally

without clinically evident shoulder dystocia or fetuses delivered by cesarean without

shoulder dystocia."    CP at 1899; see also CP at 1910 ("No published clinical or

experimental data exist to support the contention that the presence of persistent (as

compared to transient) NBPP implies the application of excessive force by the birth

attendant."). The Report, however, notes that "more investigation" is necessary. CP at

1916.


        The ACOG Report has been endorsed by several professional organizations,

including the American Academy ofPediatrics, the American College ofNurse-Midwives,

and the American Gynecological & Obstetrical Society. CP at 1878.^


        ^ It has also been endorsed by the American Academy of Physical Medicine and
Rehabilitation, the American Society for Reproductive Medicine, the Child Neurology
                                             8
L.M. V. Hamilton, No. 95173-0




          C. The trial court initially granted L.M.'s motion to exclude NFOL evidence

       At first, the trial court granted L.M.'s motion. CP at 2622-26. The court held that

under ER 702,the NFOL theory was too speculative on causation because it fails to explain

how natural forces cause avulsions and ruptures. CP at 2289-91. The court also rejected

the NFOL theory under Frye, holding that the scientific community has not reached a

"consensus" on whether "the permanent avulsion injuries can be caused by natural forces."

CP at 2290 (excerpt of court's Sept. 18, 2015 oral ruling).

          D. On reconsideration, the trial court admitted NFOL evidence

       Hamilton moved for reconsideration. CP at 2920. She listed all the courts that had

previously allowed NFOL evidence. CP at 2938-46 (citing cases). She also filed additional

expert declarations.   Dr. DeMott stated that a consensus of the relevant scientific

community now accepts "that [NFOL] can cause permanent [BPI], including brachial

nerve avulsion and rupture." CP at 2667-68. Dr. Elizabeth Sanford, another obstetrician-

gynecologist, stated that the obstetric community "agree[s] that permanent brachial plexus

injuries can be caused by [NFOL]" and that "[p]ermanent injuries include brachial plexus




Society, the Japan Society of Obstetrics and Gynecology, the Royal Australian and New
Zealand College of Obstetricians and Gynaecologists, the Society for Maternal-Fetal
Medicine, and the Society of Obstetricians and Gynaecologists of Canada. CP at 1878.
And the March of Dimes Foundation and the Royal College of Obstetricians and
Gynaecologists have offered their full support. Id.
L.M. V. Hamilton, No. 95173-0


ruptures and avulsions." CP at 2663."^ Dr. Thomas Collins, a neurologist, stated that

"[t]here is a general consensus in the medical community that permanent brachial plexus

injury can occur due to [NFOL]" and that "[tjhere is no specifically identified research

study that supports the contention that rupture and avulsion of nerves only occurs with

excessive traction." CP at 2674. Beth Coyote, a midwife, agreed. CP at 2652-53.

       The trial court then reversed its prior ruling. CP at 3246-47. Regarding Frye, the

trial court noted that an expert's "ultimate opinion" on causation "does not have to be

generally accepted so long as [his or her]... opinions are based on accepted methodology."

VRP (Oct. 12, 2015) at 26 (motion hearing). That Frye standard, the trial court held, was

satisfied in this case. Id. at 29. RegardingER702,the trial court ruled that NFOL evidence

had sufficient foundation to be helpful to the jury. See id. at 27-30. It explained that any

gaps in the science result from appropriate "ethical considerations": researchers cannot

experiment on babies to determine the force required to cause an avulsion. Id. at 28-29."

Instead, researchers must rely on peer-reviewed and published literature. Id. at 29. That

literature shows that NFOL can cause severe BPIs. Id. at 27-30. The trial court held that


this is "sufficient to bridge that analytical gap between the natural forces theory and the

injury" and reach the jury. Id. at 29.



         In an earlier declaration. Dr. Sanford had noted that the medical literature is
limited. CP at 1529("there's still quite a bit that we need to find out"), 1530("the literature
does not very specifically state" how NFOL cause permanent BPIs).

      " At trial, Dr. Mandel, L.M.'s expert, elaborated on the ethical dilemma facing
researchers: it "would be criminal to cause avulsion just to prove a medical point." VRP
(Oct. 21, 2015) at 90 (Test, of Howard Mandel, MD). "Why would you want to hurt a
baby?" Id. at 91.
                                              10
L.M. V, Hamilton, No. 95173-0


   3. The trial court allowed Dr. Tencer to testily

       The other pretrial issue before us is whether Dr. Tencer should have been allowed

to testily about the internal (endogenous) and external (exogenous) forces involved in

childbirth. CP at 2358, 2374-76. Dr. Tencer has testified approximately 250 times, but

mostly in eases involving car crashes. VRP (Oct. 27, 2015) at 9 (Test, of Allan Tencer,

PhD). Prior to this case, he had never testified in a case involving labor and delivery. Id.

He holds a doctorate in mechanical engineering, and until recently, he taught orthopedics

and sports medicine, as well as mechanical engineering, at the University of Washington.

CP at 2372-73. Dr. Tencer does not hold a medical degree. CP at 2380. Nor has he

received specialized training in the mechanics of childbirth. CP at 2372-73, 2380-81. He

has, however, researched the strength of the spinal cord and nerve roots. CP at 2373; see

flAo VRP (Oct. 27,2015)at 5-7(Test, of Allan Tencer,PhD). And to prepare for this case,

he studied the latest science on the biomeehanics of childbirth, including the ACOG

Report. CP at 2372-78; VRP (Oct. 12, 2015) at 31-32.

      In his declaration. Dr. Tencer concluded that "[fjrom a biomechanical forces

perspective, it is not possible to differentiate whether the brachial plexus nerve damage

suffered by [L.M.] resulted from exogenous, endogenous or some combination of both

forces." CP at 2376. He reached this conclusion after reviewing the current science on the

forces, including NFOL, at play. CP at 2373-76.

      L.M. opposed, arguing that Dr. Tencer, who "is not an obstetrician or a midwife,"

"is testifying far outside his expertise." CP at 3180. He also criticized Dr. Tencer's

proposed testimony as speculative and misleading because Dr. Tencer misinterpreted and

                                            11
L.M. V. Hamilton, No. 95173-0


drew "hasty generalization[s]" from the underlying literature. CP at 3180-84. For

example, L.M. claimed that Dr. Tencer "proposes to testify regarding forces that his own

published sources say are not possible." CP at 3180.

        The trial court ruled that Dr. Tencer could testify. VRP (Oct. 12, 2015) at 37-38.

The court found that he was qualified and that his testimony would help the jury understand

the forces at play, thus satisfying ER 702's prerequisites to admissibility. Id. at 37. And

it ruled that L.M. could challenge Dr. Tencer's interpretation of the underlying literature

through cross-examination. Id. But it barred Dr. Tencer from testifying about specific

causation in L.M.'s case. Id. at 34, 37. The court stated that if Dr. Tencer ignored this

limitation, it would "expect an immediate objection which will be sustained." Id. at 37-

38.'2

   4. The jury found that Hamilton was not negligent, and L.M. now appeals

        The jury found that Hamilton was not negligent. CP at 4814. L.M. appealed the

pretrial decisions to admit NFOL evidence and to allow Dr. Tencer to testify. CP at 4753.

The Court ofAppeals affirmed. L.M. v. Hamilton,200 Wn. App. 535,402 P.3d 870(2017).

        We granted review and also affirm. L.M. v. Hamilton, 191 Wn.2d 1011 (2018).

                                        Analysis


        The courts serve the gatekeeping function of keeping out "unreliable, untested, or

junk science." Anderson, 172 Wn.2d at 606 (citing 5B KarlB. Tegland, Washington



         At trial, defense counsel asked Dr. Tencer whether, in his opinion, NFOL can
"cause the rupture and avulsion of a brachial plexus." VRP (Oct. 27, 2015) at 22(Test, of
Allan Tencer, PhD). Dr. Tencer responded, "It certainly appears so." Id. Plaintiffs
counsel did not object. See id.
                                            12
L.M. V. Hamilton, No. 95173-0


Practice: Evidence Law & Practice § 702.18, at 81 (5th ed. 2007)). L.M. now argues

that the trial court's decision to admit NFOL evidence violated Frye and its decision to

allow Dr. Tencer to testify violated ER 702. We must determine whether the trial court

properly discharged its gatekeeping function.

   1. The NFOL theory is not based on novel science and thus does not violate Frye

          A. This court reviews Frye issues de novo

       We review the trial court's Frye ruling de novo. Lakey, 176 Wn.2d at 919 (citing

Anderson, 172 Wn.2d at 600). The court also reviews de novo a trial court's decision,

made outside of a Frye hearing, that the scientific community generally accepts the science

at issue and thus that no Fiye hearing is necessary. State v. Gregory, 158 Wn.2d 759, 830,

147 P.3d 1201 (2006), overruled on other grounds by State v. W.R., 181 Wn.2d 757, 336

P.3d 1134 (2014).'^

          B. Frye does not bar Hamilton's expertsfrom opining that NFOL caused L.M.'s
              avulsions and ruptures

       Frye requires experts to base their conclusions on generally accepted science.

Anderson, 172 Wn.2d at 603. The relevant scientific community must generally accept

both '"the underlying theory'" and the "'techniques, experiments, or studies'" applying



          Hamilton argues that L.M. waived his Frye challenge by failing to request a Frye
hearing below. While it is true that L.M. did not request an evidentiary hearing or in-court
testimony on the Frye issue, CP at 1460, L.M. made Frye arguments at the trial court,
including that the scientific community does not generally accept the NFOL theory, e.g.,
CP at 1475-83, 3221. And the trial court ultimately ruled on the Frye issue. VRP (Oct.
12, 2015) at 26-30. L.M. therefore preserved the issue. Cf. Johnston-Forbes, 181 Wn.2d
at 356 (holding that "'a party who fails to seek a Frye hearing below does not preserve this
evidentiary challenge for review'" {c[\xo\lmg Johnston-Forbes v. Matsunaga, 111 Wn. App.
402,408, 311 P.3d 1260 (2013)).
                                            13
L.M. V. Hamilton, No. 95173-0


that theory. Id. (quoting State v. Riker, 123 Wn.2d 351, 359, 869 P.2d 43 (1994)). The

techniques, experiments, or studies must be '"capable of producing reliable results.'" Id.

(quoting Riker, 123 Wn.2d at 359). The scientific community does not have to be

unanimous; the court should exclude the expert's opinion only "'[i]f there is a significant

dispute among qualified scientists.'" Id. (internal quotation marks omitted) (quoting

Gregory, 158 Wn.2d at 829).

      "[T]he application of accepted techniques to reach novel conclusions does not raise

Frye concerns." Lakey, 176 Wn.2d at 919. 'Hrye does not require every deduction drawn

from generally accepted theories to be generally accepted." Anderson, 172 Wn.2d at 611.

"Other evidentiary requirements provide additional protections from deductions that are

mere speculation." Id. (citing ER 104(a); ER 401; ER 403); see also id. at 603 ("'Once a

methodology is accepted in the scientific community, then application of the science to a

particular case is a matter of weight and admissibility under ER 702.'"(quoting Gregory,

158 Wn.2d at 829-30 (citing ER 702))).

       For example, in Anderson, Julie Anderson gave birth to a son, who was later

diagnosed with various "medical abnormalities." Anderson, 172 Wn.2d at 598. A doctor

opined that the son's abnormalities were likely due to Anderson's exposure to paint at work

while she was pregnant. Id. An expert agreed with the doctor and was willing to testify

that the employer's paint caused the son's birth defects. Id.

       The trial court excluded the expert's testimony under Frye because, at least at that

time, no member of the relevant scientific community had researched whether "the specific

type of organic solvents" in the employer's paint could cause "the specific type of birth

                                            14
L.M. V. Hamilton, No. 95173-0


defects at issue." Id. at 605 (emphasis added). The trial court held that Frye requires a

"consensus of scientific opinion on the issue of specific causation." Id.

       This court reversed. Id. We reiterated that trial courts should admit evidence under


Frye if the scientific community generally accepts the science underlying an expert's

conclusion; the scientifie community does not also have to generally accept the expert's

theory of specific causation. See id. at 609. It was sufficient for Anderson to "present[]

evidence that tended to show it is generally accepted by the seientific community that toxic

solvents like the ones to which Anderson was exposed . . . may damage the developing

brain of a fetus within the uterus." Id. at 610(emphasis added). Anderson did not have to

"establish that the specific causal connection between the specific toxic organic solvents

to which she was exposed and the specifie . . . birth defect is generally accepted." Id. at

611. Requiring "'general acceptance' of each discrete and ever more specific part of an

expert opinion" would place "virtually all opinions based upon scientifie data" into "some

part of the scientific twilight zone." Id. Because the court found nothing novel about the

science underlying the expert's testimony, it held that the testimony did not implicate Frye.

Id. at 611-12.


       In this case, Hamilton argues that the scientific community generally accepts that

NFOL could have caused L.M.'s BPI. Although the literature is silent as to avulsions and

ruptures, she argues, it does say that NFOL can cause permanent BPIs. And because the

category of permanent BPIs includes avulsions and ruptures, Hamilton argues that NFOL

could have caused L.M.'s BPI.




                                             15
L.M. V. Hamilton, No. 95173-0


       Meanwhile, L.M. argues that the relevant scientific community does not generally

accept that NFOL can cause his specific BPI—rupture and avulsion at all five nerve roots.

He notes that the literature is silent as to whether NFOL can cause such a severe BPI.

Although L.M.'s own experts recognize that the literature suggests that NFOL can cause

permanent BPIs, they disagree over what types of permanent BPIs (e.g., severe stretching,

avulsions, ruptures) this includes.

       Anderson resolves this dispute: ''Frye does not require every deduction drawn from

generally accepted theories to be generally aceepted." 172 Wn.2d at 611. For Frye

purposes, Hamilton does not have to prove that the relevant scientific community generally

accepts that NFOL could have caused L.M.'s ruptures and avulsions—much like Anderson

did not have to prove general acceptance of"the specific causal connection" in her case. It

is suffieient for Hamilton to draw such a deduction from generally accepted science. Here,

Hamilton's experts note that the science shows that NFOL can cause permanent BPIs.

From this they deduce that NFOL can cause avulsions and ruptures, both of which are types

of permanent BPIs. So long as the science underlying this deduction is generally accepted,

Frye is satisfied.

       Requiring general acceptance of "each discrete and ever more specific part of an

expert opinion" (e.g., requiring general acceptance that NFOL can cause specific types of

permanent BPIs) would place "virtually all opinions based upon scientific data" into "some

part ofthe scientific twilight zone." Id. Other evidentiary rules—not Frye and not at issue

here—bar deductions that are too speculative.



                                            16
L.M. V. Hamilton, No. 95173-0


       In sum, Hamilton must show that her experts based their opinions on generally

accepted science.

           C. Hamilton's experts based their opinions on generally accepted science

       Hamilton's experts testified thatNFOL caused L.M.'s avulsions and ruptures. They

based this testimony on the underlying theory that NFOL can cause permanent BPIs and

on the literature surrounding that theory. To determine whether this satisfies Frye, we look

to "a number of sources," including the "record, available literature, and the cases of other

jurisdictions." State v. Baity, 140 Wn.2d 1, 10, 991 P.2d 1151 (2000) (citing State v.

Cauthron, 120 Wn.2d 879, 888, 846 P.2d 502 (1993)).

       These sources reveal a generally accepted theory: NFOL can cause permanent BPIs.

This theory has developed from retrospective analyses of data and experiments that rely on

modeling, rather than on prospective experiments, because researchers cannot ethically

perform experiments on infants to determine exactly how much force causes the various

types of BPIs. Although the ethical limitations prevent researchers from performing some

studies, it does not follow that the studies they can perform are incapable of producing

reliable results. Nor does it matter, for Frye purposes, that more investigation and research

in the future will likely lead to even better results. What matters is that the theory is

generally accepted and that the techniques, experiments, and studies applying that theory

are also generally accepted and capable of producing reliable results. And that is clearly

the case here. The ACOG Report, for example, reviewed published literature, which was

reviewed for quality, and has been endorsed by several prominent organizations from

around the world.

                                             17
L.M. V. Hamilton, No. 95173-0


       L.M. fails to show that there is a significant dispute among scientists. In fact, L.M.'s

own experts recognize that the literature suggests that NFOL can cause permanent BPIs.

See VRP (Oct. 21, 2015) at 119 (Test, of Howard Mandel, MD); VRP (Oct. 22, 2015) at

115 (Test, of Stephen Glass, MD). Moreover, at the trial court, all ofL.M.'s cited literature

suggesting otherwise was authored by one person. Dr. Michael S. Kreitzer, and was

published before the ACOG Report. In his supplemental brief before this court, L.M. does

include two additional publications not authored by Dr. Kreitzer. Suppl. Br. ofPet'r at 15-

16. But neither publication reveals a significant dispute in the scientific community. In

fact, the first acknowledges that excessive traction is not the only possible cause of BPIs:

       There is enough evidence that BPI can occur in the absence of shoulder
       dystocia to conclude that not every injury is the consequence of excessive
       force applied by the obstetrician or midwife. Moreover, it seems equally
       clear that BPI can occur in association with shoulder dystocia even when the
       complication has been managed optimally. The weight of the available
       information suggests, however, that inopportune medical intervention is
       probably a factor in most injuries.

Id. App. 1 at 001 (internal citations omitted). And the second appears to answer the Frye

inquiry in favor of Hamilton:"[Ajmong American obstetricians the idea that most injuries

develop 'in utero' spontaneously has gained wide acceptance.'" Id. App. 2 at 006 (second

emphasis added).



         The author goes on to argue that American obstetricians favor the NFOL theory
because the "idea offers a firm ground for defending malpractice claims." Suppl. Br. of
Pet'r App. 2 at 006; see also Taber v. Roush, 316 S.W.3d 139, 180 (Tex. App. 2010)
(Anderson, J., dissenting)("I believe that much of[the literature] was motivated in no small
part by concerns over the amount of litigation involving brachial plexus injuries and the
lack of a viable defensive theory in the face of the only generally accepted cause of those
injuries: excessive traction by the delivering physician."). And L.M. notes that "[sjome of
the articles reference litigation as a consideration." Pet. for Review at 11.
                                             18
L.M. V. Hamilton, No. 95173-0


       Other jurisdictions agree. L.M. points us to only one court that has excluded NFOL

evidence in a BPI case under Frye. That court, from New York, affirmed a lower court's

holding that the NFOL theory is "a novel theory subject to a Frye analysis" and is "not

generally accepted within the relevant medical community." Muhammad, 91 A.D.Bd at

1354. But the court applied an abuse of discretion standard, rather than conduct de novo

review, and provided almost no reasoning. Id. And in a similar case, another New York

court distinguished Muhammad and held that defendants' NFOL theory satisfied the Frye

standard. Nobre, 42 Misc. 3d at 924-25.'^         There, the court reasoned that it could not

"conceive how a theory that has been studied, tested and debated for more than twenty

years can be deemed to be novel." Id. at 922.'® Other Frye jurisdictions have reached a

similar conclusion. E.g., Ruffin ex rel. Sanders v. Baler, 384 111. App. 3d 7, 22-25, 890

N.E.2d 1174,(2008).




        But even if litigation motivated the science, it does not necessarily follow that the
scientists manipulated the techniques, experiments, or studies to reach a desired result.
Moreover, 10 professional organizations—from around the world—endorsed the 2014
ACOG Report. Finally, L.M. had every opportunity to draw out potential biases of the
cited medical literature during cross-examination of Hamilton's experts—and in fact did
so. E.g., VRP (Oct. 28, 2015) at 61-64 (Test, of Robert DeMott, MD).

          The Nobre court distinguished Muhammad in part because Muhammad involved
"at least a partial avulsion," while Nobre involved "no rupture or avulsion." 42 Misc. 3d
at 924. But it also distinguished Muhammad because the Muhammad court conducted a
more limited review of the medical literature. Id. at 924-25.


      '® The court in Nobre went on to exclude the theory for lack of foundation. Id. at
924-30.


                                             19
LM. V. Hamilton, No. 95173-0


       In sum, Hamilton's experts eoneluded that NFOL caused L.M.'s avulsions and

ruptures, and they based this conclusion on generally accepted science. Because Frye is

not implicated, we affirm the trial court's Frye determination to deny L.M.'s motion to

exclude evidence of the NFOL theory.

   2. The trial court did not abuse its discretion by allowing Dr. Tencer to testify

       "The trial court must exclude expert testimony involving scientific evidence unless

the testimony satisfies . . . ER 702." Lakey, 176 Wn.2d at 918 (citing State v. Copeland,

130 Wn.2d 244, 255-56, 922 P.2d 1304 (1996)). Expert testimony satisfies ER 702 if(1)

"the witness qualifies as an expert," and (2)"the testimony will assist the trier of fact." Id.

(citing Cauthron, 120 Wn.2d at 890 (citing ER 702)).'^

       We review for abuse of discretion the trial court's admission of expert testimony

under ER 702. Lakey, 176 Wn.2d at 919 (citing State v. Yates, 161 Wn.2d 714, 762, 168

P.3d 359 (2007)). "A trial court abuses its discretion by issuing manifestly unreasonable

rulings or rulings based on untenable grounds, such as a ruling contrary to law." Id. (citing

Wash. State Physicians Ins. Exch. & Ass'n v. Fisons Corp., 122 Wn.2d 299, 339, 858 P.2d

1054 (1993)). A reviewing court may not hold that a trial court abused its discretion




         In recent years, we have oeeasionally expressed a three-part test in which we also
require the expert to rely on generally accepted theories. Gilmore v. Jefferson County Pub.
 Transp. Benefit Area, 190 Wn.2d 483, 495, 415 P.3d 212 (2018); Johnston-Forbes, 181
Wn.2d at 352; In re Pers. Restraint of Morris, 176 Wn.2d 157, 168-69, 288 P.3d 1140
(2012); In re Marriage of Katare, 175 Wn.2d 23, 38, 283 P.3d 546 (2012). But that
additional general acceptance part is really a Frye determination. "Because we review a
Frye determination de novo, but review issues under ER 702 only for abuse of discretion,
we find it inappropriate to include a Frye determination as part of the test for proper
admissibility of expert testimony under ER 702." Cauthron, 120 Wn.2d at 890 n.4.
                                             20
L.M. V. Hamilton, No. 95173-0


"'simply because it would have decided the case differently.'" Gilmore v. Jefferson County

Pub. Transp. Benefit Area, 190 Wn.2d 483, 494, 415 P.3d 212 (2018)(quoting State v.

Salgado-Mendoza, 189 Wn.2d 420,427,403 P.3d 45(2017)). To find abuse of discretion,

a court "'must be convinced that'"no reasonable person would take the view adopted by

the trial court.""" Id. (emphasis added)(quoting Salgado-Mendoza, 189 Wn.2d at 427

(quoting State v. Perez-Cervantes, 141 Wn.2d 468,475,6 P.3d 1160(2000)(quoting State

V. Huelett, 92 Wn.2d 967, 969, 603 P.2d 1258 (1979)))). '"[I]f the basis for admission of

the evidence is fairly debatable,'" a court "'will not disturb the trial court's ruling.'" Id.

(internal quotations omitted)(quoting Grp. Health Coop, ofPuget Sound, Inc. v. Dep 't of

Revenue, 106 Wn.2d 391, 398, 722 P.2d 787(1986)).

          A. The trial court did not abuse its discretion in ruling that Dr. Tencer was
             qualified to testify

       A witness may qualify as an expert "by knowledge, skill, experience, training, or

education." ER 702. "An expert may not testify about information outside his area of

expertise." In re Marriage ofKatare, 175 Wn.2d23,38,283 P.3d 546(2012)(citing Queen

City Farms, Inc. v. Cent. Nat'l Ins. Co. ofOmaha, 126 Wn.2d 50, 104, 882 P.2d 703, 891

P.2d 718 (1994)(plurality opinion)). When determining whether a witness is an expert,

courts should look beyond academic credentials. Harris v. Robert C. Groth, MD,Inc., 99

Wn.2d 438,449-50,663 P.2d 113(1983). For example, depending on the circumstance, a

nonphysician might be qualified to testify in a medical malpractice action. Id. '"[T]he line

between chemistry, biology, and medicine is too indefinite to admit of a practicable

separation of topics and witnesses.'" Id. at 450 (quoting 2 JOHN HENRY WiGMORE,


                                             21
L.M. V. Hamilton, No. 95173-0


Evidence in Trials at Common Law § 569, at 790 (rev. 1979)). But when making the

determination, courts must consider whether the expert has '"sufficient expertise in the

relevant specialty.'" Frausto v. Yakima HMA, LLC, 188 Wn.2d 227, 232, 393 P.3d 776

(2017)(quoting Young v. Key Pharm., Inc., 112 Wn.2d216, 229, 770 P.2d 182(1989)).

       Parties often call Dr. Teneer to testify as an expert, typically in eases involving

automobile collisions. Sometimes his testimony has been admissible, sometimes it has not.

In Stedman v. Cooper, for example, the trial court barred Dr. Teneer from testifying. 172

Wn. App. 9, 13, 292 P.3d 764(2012). Applying an abuse of discretion standard, the Court

of Appeals affirmed, holding that Dr. Teneer's "clear message was that Stedman could not

have been injured in the accident because the force of the impact was too small." Id. at 20.

In Ma'ele v. Arrington, in contrast, the trial court admitted Dr. Tencer's testimony. 111

Wn. App. 557, 560, 45 P.3d 557 (2002). Like in Stedman, Dr. Teneer "expressed no

opinion about Ma'ele's symptoms or possible diagnosis from those symptoms." Id. at 564.

Applying an abuse of discretion standard, the Court of Appeals affirmed, stating that the

jury was "entitled to infer" from Dr. Tencer's testimony that Ma'ele was injured in the

crash. Id. 563-64.


       The apparent inconsistency between Stedman and Ma'ele is due to the abuse of

discretion standard. Johnston-Forbes, 181 Wn.2d at 353. '"The broad standard of abuse

of discretion means that courts can reasonably reach different conclusions about whether,

and to what extent, an expert's testimony will be helpful to the jury in a particular case.'"

Id. at 353-54(quoting Stedman, 172 Wn. App. at 18). The broad standard also means that

courts can reasonably reach different conclusions about whether an expert is qualified.

                                            22
L.M. V. Hamilton, No. 95173-0


      In this case, L.M. argues that Dr. Tencer was not qualified to testify at all because

he lacked expertise in the forces of childbirth. On the one hand, courts must determine

whether an expert has "sufficient expertise in the relevant specialty." Frausto, 188 Wn.2d

at 232. Dr. Tencer does not have remarkable expertise in the biomechanics of childbirth;

until his retirement, he taught orthopedics and sports medicine. But on the other hand, the

evidence rules say that a witness may qualify as an expert"by knowledge, skill, experience,

training, or education." ER 702 (emphasis added). Although Dr. Tencer is not specially

trained in the biomechanics of childbirth, he is highly qualified to testify about

biomechanical forces in general. He has also personally researched the spine. CP at 2372-

73. And to prepare for this case, he looked at the latest science regarding the biomechanics

of childbirth. Id. at 2372-78; VRP (Oct. 12, 2015) at 31-32. As the AGOG Report notes,

"biomechanics is a means through which the causes of[BPIs] have been and continue to

be investigated and understood." CP at 2424. Dr. Tencer, a biomechanical engineer, is

able to read the latest science, learn the forces at play, and apply that new knowledge to

what he already knows about the spine.

       This is a close call. But "'[i]f the basis for admission of the evidence is fairly

debatable,'" a court'"will not disturb the trial court's ruling.'" Gilmore, 190 Wn.2d at 494

(internal quotation marks omitted)(quoting Grp. Health Coop., 106 Wn.2d at 398). The

trial court did not abuse its discretion in ruling that Dr. Tencer was qualified to provide

biomechanical testimony.




                                            23
L.M. V. Hamilton, No. 95173-0


          B. The trial court did not abuse its discretion in finding that Dr. fencer's
             testimony was helpful to ajury

       Courts find an expert's testimony to be helpful if it helps "the jury's understanding

of a matter outside the competence of an ordinary layperson." Reese v, Stroh, 128 Wn.2d

300,308, 907 P.2d 282(1995)(citing           v. Ciskie, 110 Wn.2d 263, 279, 751 P.2d 1165

(1988); Riggins v. Bechtel Power Corp., 44 Wn. App 244, 254, 722 P.2d 819 (1986)).

"Unreliable testimony does not assist the trier of fact." Lakey, 176 Wn.2d at 918 (citing

Anderson, 172 Wn.2d at 600). Neither does testimony lacking an adequate foundation.

Johnston-Forbes, 181 Wn.2d at 357; Walker v. State, 121 Wn.2d 214, 218, 848 P.2d 721

(1993). "It is the proper function of the trial court to scrutinize the expert's underlying

information and determine whether it is sufficient to form an opinion on the relevant issue."

Johnston-Forbes, 181 Wn.2dat357.

       Quantifying the forces of labor is obviously outside the competence of an ordinary

layperson. Instead, L.M. argues that Dr. Tencer used data inappropriately to reach a

preordained conclusion. Pet. for Review at 17. L.M. takes issue with Dr. Tencer's

testimony regarding the force necessary to injure the brachial plexus because "virtually all

the medical literature states that this force is not known and cannot be known,"Id. at 2; see

also id. at 18. But that force is difficult or even impossible to know in large part because

of ethical considerations, and the trial court was aware of this. VRP (Oct. 12, 2015) at 28-

29. Although the ethical considerations leave an analytical gap in the science, the trial

court found the analytical gap satisfactorily "bridge[d]" by the current literature showing

that NFOL can cause permanent BPIs. Id. at 29. The trial court ruled that any concerns


                                            24
L.M. V. Hamilton, No. 95173-0


over Dr. Tencer's use of the data and any other concerns over the literature would make

"excellent arguments for cross-examination." Id. at 37.

      The trial court's thoughtful review of the helpfulness prong was not manifestly

unreasonable and thus was not an abuse of discretion.


                                       Conclusion


       We affirm the trial court and hold that (1) it correctly admitted NFOL evidence

under Frye and (2) it did not abuse its discretion by allowing Dr. Tencer to testify.




                                            25
L.M. V. Hamilton, No. 95173-0




WE CONCUR:




^t\AA               , 0^




                                     J / P.



                                26
LM. V. Hamilton




                                     No. 95173-0


      GonzAlez, J.(concurring in result only)—Allan Tencer, PhD,should not

have testified in this case. The trial court committed error in allowing him to

testify. I respectfully disagree with the majority's assertion that this is a close call.

However, because I believe that the error was ultimately harmless, I concur.

      Tencer is not qualified to testify about the forces involved in childbirth. See

In re Marriage ofKatare, 175 Wn.2d 23, 38, 283 P.3d 546(2012)("An expert

may not testify about information outside his area of expertise." (citing Queen City

Farms, Inc. v. Cent. Nat'l Ins. Co. of Omaha, 126 Wn.2d 50, 104, 882 P.2d 703,

891 P.2d 718 (1994)(plurality opinion))). Tencer is a biomechanical engineer

with a background in the forces involved in automobile accidents and the effect

such forces may have on the human body. While it may not be error to admit his

expert testimony in automobile accident cases, it is error under these facts.

Compare Johnston-Forbes v. Matsunaga, 181 Wn.2d 346, 355, 333 P.3d 388

(2014)(affirming the limited admission of Tencer's testimony in an automobile

accident case), with Gilmore v. Jefferson County Pub. Trans. Benefit Area, 190

Wn.2d 483, 498, 415 P.3d 212(2018)(affirming the exclusion of Tencer's
LM. V. Hamilton, No. 95173-0 (Gonzalez, J., concurring in result only)


testimony in an automobile accident case because "it would create unreasonable

inferences, and confuse and mislead the jury").

       The majority appears to accept that being a biomechanical engineer qualifies

Tencer to abstractly discuss the forces involved in childbirth. But finding that an

expert is qualified requires more than a highly educated person's cursory review of

relevant data; "'[t]he scope of the expert's knowledge'" governs. Frausto v.

YakimaHMA, LLC, 188 Wn.2d 227, 234, 393 P.3d 776(2017)(alteration in

original)(quoting 77/// v. Sacred Heart Med. Ctr., 143 Wn. App. 438, 447, 177

P.3d 1152(2008)). In Frausto, we explained that whether a nurse "has the

requisite specialized knowledge to qualify as an expert on causation" depends on

the nurse's "particular scope of practice and expertise." Id. at 243. Tencer admits

to having no scope of practice and expertise regarding the forces involved in

childbirth. He admitted this on direct examination:


       Q: Have you ever done a labor and delivery case before this one?
       A: No,I have not.
Verbatim Report ofProceedings(VRP)(Oct. 27, 2015) at 9. And again on cross-

examination. Id. at 26 ("I've never been involved in labor and delivery.").

Further, there is no indication that Tencer's general work regarding the human

spine directly translates to the specific circumstances involved in neonatal brachial

plexus injuries.
LM. V. Hamilton, No. 95173-0 (Gonzalez, J., concurring in result only)


       The majority's reasoning that Tencer, as "a biomechanicai engineer, is able

to read the latest science, learn the forces at play, and apply that new knowledge to

what he already knows about the spine" is erroneous, dangerous, and

presumptuous. Majority at 27. Tencer's review of a single report discussing the

forces involved in childbirth does not qualify him to testify. Allowing him to

testify runs contrary to our focus on the expert's relevant experience. See, e.g.,

Katare, 175 Wn.2d at 38-39(holding an attorney with "17 years of experience in

the field of child abduction" cases was qualified to testify about risk factors for

child abductions). In other words, under the majority's reasoning, any attorney

who reads a paper on child abductions in preparation for trial would be qualified to

testify as a child abduction expert.

       Further, Tencer puts forward an improperly speculative opinion based on

insufficient underlying data that "he looked at." See majority at 26("And to

prepare for this case, he looked at the latest science regarding the biomechanics of

childbirth."). This is simply not enough. "[Cjourts must scrutinize the expert's

underlying information ... to ensure that the opinion is not mere speculation,

conjecture, or misleading.'''' Johnston-Forbes, 181 Wn.2d at 358 (emphasis added)

(citing Stedman v. Cooper, 111 Wn. App. 9, 18, 292 P.3d 764(2012)). The report

Tencer relies on expressly concludes that "there are no data to quantify the
L.M. V. Hamilton, No. 95173-0 (Gonzalez, J., concurring in result only)


threshold pressures needed to induce traction versus compression related nerve

injury." Clerk's Papers at 3204. That report warns that

       the assumptions in this study used to calculate the maternal expulsive
       efforts were actually generated under normal conditions rather than
       during an obstructive process . ...[which] suggests that these data
       may have underestimated those maternally derived forces and that
       during a shoulder dystocia event there may be an even greater
       divergence of attributable forces between endogenous and exogenous
        sources.



Id. Thus, Tencer's opinions regarding the comparative forces involved in

childbirth, as they relate to the primary contested issue in this case—

causation—cannot be supported by the very information on which his

opinion is purportedly based.'

        The trial court barred Tencer from opining directly on the issue of

causation but ruled that he could testify generally to help the jury understand

the forces at play. But general "[sjcientific evidence that does not help the

trier of fact resolve any issue of fact. . . does not meet the requirements of


'The majority acknowledges this "analytical gap" in the underlying data but appears to confuse
the trial court's Frye determination about the general acceptance of the science undergirding the
natural forces of labor theory with the determination of whether Tencer's specific testimony was
based on sufficient underlying data. See majority at 28; Frye v. United States, 54 App. D.C. 46,
293 F. 1013 (1923). Even if the science generally allows for a medical causation opinion, it does
not support the conclusion that Tencer could adequately testify, particularly when his
nonmedical expert opinion was offered to induce an inference about medical causation. See
Stedman, 111 Wn. App. at 20 (trial court excluding Tencer's testimony in automobile accident—
and upheld on appeal—because his "clear message" was causation).
       It should also be noted that the majority's affirmation of the trial court's Frye
determination in this case—finding that the natural forces of labor theory is currently generally
accepted in the scientific community—does not foreclose the possibility of a successful
challenge to the theory at a future Frye hearing, as the underlying science continues to develop.
LM. V. Hamilton, No. 95173-0 (Gonzalez, J., concurring in result only)


ER 702." State v. Greene, 139 Wn.2d 64, 73, 984 P.2d 1024(1999)(citing

Reese v. Stroh, 128 Wn.2d 300, 311, 907 P.2d 282(1995)(Johnson, J.,

concurring)). Here, the primary issue in dispute at trial was causation, which

Tencer was specifically prohibited from testifying about. The specific

"forces at play" in this case were not known, and Tencer never considered

those specific forces in forming his opinion testimony.^

       Additionally, despite being expressly prohibited from testifying about

medical causation, it appears Tencer's testimony informed a medical

causation inference. See Stedman, 172 Wn. App. at 20. Nonetheless,

whatever effect Tencer's improper testimony may have had on the jury's

medical causation determination, it was likely insignificant when compared

to the medical causation evidence admitted through otherwise qualified

medical experts. See Brown v. Spokane County Fire Prot. Dist. No. 1, 100

Wn.2d 188, 196, 668 P.2d 571 (1983)("We find that the evidence, being

merely cumulative in nature, was harmless error."). Therefore, Tencer's

testimony was ultimately harmless and I concur in result.




^ At trial, Tencer confirmed that "nobody measured the force in Ms. Hamilton's hands if she used
any in facilitating [L.M.J's birth." VRP (Oct. 27, 2015) at 16. Additionally, in his discussion of
the average endogenous forces involved in labor, Tencer emphasized "that these numbers don't
apply specifically to this case." Id. at 15.
LM. V. Hamilton, No. 95173-0 (Gonzalez, J., concumng in result only)




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