FI L ED U.S. COURT OF APPEAL S EL EVENTHCI RCUI T J UNE 22, 2010 J OHN L EY CL ERK [PUBLIS H] IN THE UN ITED STATES COURT OF APPEALS FOR THE ELE VENTH CIRCUIT

__ __ __ __ __ __ __ __ __ __ __ __ No. 0 9- 10 07 9

__ __ __ __ __ __ __ __ __ __ __ __ D. C. Dock etNo. 0 7- 00 13 3- CV-3 -MC R-EMT RHONDA HEND RIX, Pare ntan d Gu ard ian o f G.P., a m in orch il d, Pl ai nt iff -Co un te r Defen da nt -Ap pe ll an t,
ve rs us EVENFLO COMPANY, INC., a fo rei gn co rp or at io n Defen da nt -Co un te r Cl ai m an t-Ap pe ll ee, FORT WALTON BEACH MEDICAL CENTE R, a Fl or id a co rp or at io n, Defen da nt .

__ __ __ __ __ __ _ App eal fro m

th e Uni te d S ta te s Di st ric t Co urt fo r th e North ern Dis tri ctof F lo rid a

__ __ __ __ __ __ _ (J un e 2 2, 2 01 0) Befo re CARNES, HULL andANDERSON, Circu itJu dg es . ANDERSON, Circ ui t J ud ge :Pl ai nt iff -Ap pe ll an t Rh on daHend rix all eg es th athe r so n, G.P., su st ai ne d traum at ic bra in in

juri es when a ch il d re st rai ntsyste m m anuf actur edby D efen da nt App el le e Eve nf

lo Co m pa ny, Inc., (“ Eve nf

lo ”), m al fu nc ti on eddu rin g am in ortra ffi c acci de nt . Hend rix furth er al le ge s t ha t tho se bra in in juri es cau se d G.P. t o d ev el op au ti sm sp ect ru m di so rd er (“ ASD”) an d asp in al co rdde fectkn own as syrin go m y el ia . The d is tri ctco urt ex cl ud edtes ti m on y fro m two of He nd rix ’s exp ert wit ne ss es th atth e acc id en t caus edG.P.’ s ASD. The di st ric t co urt co nc lu de d t ha t th e m etho ds us edby H en dr ix ’s exp ert s wer e n otsu ffi ci en tl y rel iabl e u nd er Dau be rt v. Merre ll

Down Pha rma ceu ti ca ls , Inc
. , 50 9 U.S. 5 79 , 11 3 S . Ct. 2 78 6 (1 99 3)
. Hen dr ixv. Even

fl o C o., In c. , 25 5 F .R.D. 56 8 (N.D. Fl a. 20 09 ). The d is tri ctco urt th engra nt edpa rti al su m

m ary jud gm en t t o Ev en flo onHend rix ’s com pe ns at ory da m ag es cla im , det erm in in g t ha t wi th ou t t he ex cl ud edtes ti m on y th ere was no rel iabl e ev id en ce t o s up po rt He nd rix ’s th eo ry th atth e acc id en t caus edG.P.’ s ASD. Hen dr ix vo lu nt ari ly dis m is se d, wi th pre jud ic e, he r rem ai ni ng da m ag es cla im s an d fil eda no ti ce o f ap pe al
.

I. FACTS AND PROCEDURAL HISTORY The pro du ctat i ss ue in th is pro du ctli ab il it y cas e is th e Eve nf

lo Dis co ve ry Mo de l 2 12 Ch il d R es tra in t Syste m (“ th e CRS ”) o wne d b y

Hend rix . The CR S, whi chwas m anuf

actur edin Decem

be r 20 00 , con si st s o f a p la st ic ba se th atis 2se cu redto th e v eh ic le ’s sea t b y th e sa fet y

be ltan d apa dd edpl as ti c carrie r. The
carr ie r is eithe r lo ck edin to th e b as e o r se cu reddi rect ly to t he ve hi cl e’s se atwith a
sa fet y be lt . The CR S m eet s the requi rem en ts im po se d b y fed eral reg ul at io ns . Se e 49 C.F.R. § 57 1.2 13 . Whe n u se d p ro pe rly, the ba se is po si ti on edin a rearsea t wi th th e carrie r lo ck edin to th e b as e so th e ch il d fa ces th e rea r of th e v eh ic le
. On Ap ril 17 , 20 02 , Hend rix an d h er fi fte en -d ay -o ldso n, G.P., were i nv ol ve d in a m in ortra ffi c acc id en t (“ th e acc id en t” ) whi le tra ve li ng at asp eedof 1 0- 12 m ph
. Hen dr ix cla im s t ha t G.P. was pro pe rly str ap pe d i nt o t he CRS, an d t ha t t he CRS was lo cat edin th e rea r cen te r po si ti on of h er SUV. Hend rix ’s th eo ry is th atdu rin g t he 1 acci de ntth e se atdi sl od ge d fr om it s b as e b ecau se itha d b een “ fal se -la tc he d.” A fal se -la tc h o ccurs whenth e m ech an is m th atatt ach es th e carrie r to th e b as e fai ls to pr op erl y lat ch ev enth ou gh th e la tc h m ak es anau di bl e cl ic k l ead in g t he pe rs on in st al li ng th e se atto be li ev e th e se atis pro pe rly ins ta ll ed . Hend rix arg ue s t ha t be cau se of the fal se -la tc h t he carr ie r se pa rat edfro m th e b as e atim

pa ctan d s tru ck th e co ns ol e b etween th e SUV’s fro ntsea ts .

For purposes of this appe al, we a ssume Hendr ix ’s ver sion of the fa cts that the 1 car rier a nd the child wer e snappe d into the base in the re ar c enter position of the SUV. It is undisputed that the base of the CRS was in the rear

cente r seat, secure d by

a saf ety belt. Howeve r, Evenf

low’s theory

is that the car

rier a nd the child wer e ac tually positioned in the front passeng er se at of the SUV in c ontrave ntion of the CRS safe ty instructions and in violation of state law. Eve nflow ar gues that, due to the inc orre ct positioning of the c arrier, during impact the car rier struc k or wa s struck by the front pa sseng er- side airba g .

3It i s u nd is pu te d t ha t t he carr ie r frac tu reddu rin g t he acci de nt . Whi le itis als o

un di sp ut edth atG.P. su ffer eda cl os ed -h eadin jury as a res ul t o f th e acc id en t, the pa rti es do di sp ut e th e se ve rit y of t he in jury andwhet he r G.P. su ffer edbra in da m ag e. G.P.’ s m ed ic al reco rd s re ve al th athe su ffer ed , at t he ve ry lea st , a co ntus io n o n h is for eh eadan d b le ed in g i n h is bra in . G.P.’ s i nju rie s d o n otap pe ar to ha ve cau se d i m

m ed ia te ne ur ol og ic im

pa irment, a s G.P. ex hi bi te d n o de ve lo pm en ta l p ro bl em s athi s 2 , 4, o r 10 -m on thch eck -ups . Nearl y eig ht eenm on th s af

te r th e acc id en t, G.P. b eg anto ex hi bi t de ve lo pm en ta l p ro bl em s. Whenoc cupa ti on al th erap y fai le d t o c au se im

pr ov em en t, G.P. was re ferr edto Dr. Suh rb ie r, a p ed ia tri c n eu ro lo gi st . Dr. Suh rb ie r adm in is te reda ne ur ol og ic ev al ua ti on to ad dr es s G.P.’s s ev ere n eu ro de ve lo pm en ta l de la y , im pa ire d s oc ia l i nt erac ti on s, an d h is to ry of s ei zures . App ro xi m at el y

th ree years a fte r th e acc id en t, Dr. Su hrbi er d ia gn os edG.P. wit h a n a sym

pt om at ic sp in al co rdcy st . Hend rix arg ue s t ha t t he cy stis a syrin go m y el ia , whi ch can be cau se d b y traum a b utm ay

no t ap pe ar fo r se ve ral y ears fo ll owi ng th e cau sa ti ve traum a. 2 Dr. Suh rb ie r di ag no se d G.P. wi th ASD inApri l 2 00 7, wh enG.P. was fi ve
Evenflo sug g ests that, instead, the c y st is a hydromyelia re sulting fr om a 2 cong enital def

ect in G.P.’s bra in. 4y ears ol d. Th ere i s l it tl e in fo rm at io n i n t he reco rdreg ard in g G.P.’s curren t

im pa irments rel at edto hi s ASD d ia gn os is . A repo rt f il edin Decem

be r 20 07 by Hen dr ix ’s sec on d m ed ic al ex pe rt, Dr. Ho ffm an , des cri be s G.P. as co m pl et el y 3
no nv erb al , agg res si ve , lac ki ng fin e m ot or sk il ls , andrefu si ng or u nabl e to us e ut en si ls , andas s uf

feri ng fro m

de la y edsl eep -o ns et , hyperac ti vi ty (i.e., co ns ta nt
m ot io n, ru nn in g a way ), an d d ecre as edres po ns e to pa in . Bas edon in fo rm at io n pr ov id edby H en dr ix an d h is pe rs on al ex am in at io ns of G.P., Dr. Hof fm an co nc lu de d t ha t G.P. h as “ au ti sm sp ect ru m di so rd er, a b eh av io ral ly defi ne d d is or de r wit h qua li ta ti ve ly im

pa ire d s oc ia l i nt erac ti on , qu al it at iv el y im pa ire d
co m m un ic at io n (n otco m

pe ns at edby ges tu re), an d re st ric ti ve rep et it iv e an d st ereo typedpa tt ern s o f be ha vi or , in te res ts an d a ct iv it ie s.” Ev en flo ’s m ed ic al
ex pe rt, Dr. Ep st ei n, al so ex am in edG.P. andde sc rib edim pa irments co ns is te ntwith th os e d es cri be d b y

Dr. Hoffm an . The ex pe rts all ag ree tha t, as a res ul t o f hi s ASD, G.P. wil l n ev er b e g ai nf

ul ly em pl oyed. On Ap ril 12 , 20 06 , Hend rix fil edsu itag ai ns t Ev en flo bo th in di vi du al ly and
on be ha lf o f G.P., cla im in g t he de fect iv e CRS cau se d G.P. t o s us ta in in juri es th at ul ti m at el y

ledhi m to de ve lo p ASD an d s yrin go m y el ia . Even flo rem ov edth e cas e

Dr. Hof fman is a medic al doctor who is board-c ertified in ne urodeve lopmental 3 disabiliti es and de velopmental-be haviora l pediatrics. 5to th e North ern Dis tri ctof F lo rid a o n t he ba si s o f di ve rs it y juri sd ic ti on . The p art ie s th enco m m en ceddi sc ov ery. Hen dr ix so ug htto in tro du ce t es ti m on y by D r. Su hr

bi er an d Dr. Ho ffm anth at th e in juri es G.P. su st ai ne d i n t he acci de ntcau se d h im to de ve lo p ASD an d syrin go m y el ia . Even flo m ov edto ex cl ud e th is tes ti m on y , cit in g a s o ne ba si s fo r ex cl us io n t he factth atth ere i s n o s ci en ti fic al ly reli ab le ba si s fo r th e ex pe rts ’ op in io ns , as re qu ire d b y Dau be rt . The di stric t co urt as se ss edth e ad m is si bi li ty of Dr. Suhrbi er’s t es ti m on y ba se d o n Dr. Su hrbi er’s d ep os it io n t ak enby E ve nf lo in Ju ly, 20 07 , andDr. Su hrbi er’s p os t-d is co ve ry affi da vi t p rep aredonSep te m be r 9, 2 00 8. Inhi s de po si ti on , Dr. Suh rb ie r st at edth at“ reco gn iz edcau se s o f au ti sm in cl ud e g en et ic di so rd ers , m et ab ol ic di so rd ers , epi le pt ic en cep ha lo pa th ie s, s tru ctur al in juri es an d
m al fo rm at io ns to th e b rai n, as well as r eas on s t ha t h av e n otbe enful ly elu ci da te d.” Dr. Suh rb ie r al so cla im edth atau ti sm ha d b een ass oc ia te d wi th sev ere h eadin jury
an d s ta te d h is op in io n t ha t t he re was a “ hi gh pro babi li ty” th e acc id en t h adcau se d G.P.’ s ASD. Whenask edforsci en ti fic or m ed ic al li te ratur e rel at in g aut is m sp ect ru m di so rd ers an d t rau m a, ho wev er, Dr. Su hrbi er s ta te d t ha t h e co ul d n otcit e fro m m em ory any sp eci fic art ic le s. Inhi s p os t-d is co ve ry

affi da vi t, Dr. Suhrbi er s ta te d tha t h is di ag no si s o f G.P.

6was ba se d o n:

pe rs on al ex am in at io ns , in te ract io n wi th an d o bs erv at io ns of [ G.P.] , te st in g t ha t I h adpe rfo rm edonhi m , m y rev ie w of s om e o f hi s m ed ic al reco rd s, m

ul ti pl e in te rv ie ws wi th hi s p rimary care gi ve r, m

y tra in in g, educ at io n a ndex pe rie nc e, m y own ba se of kno wled ge an d th e u ti li zat io n o f th e g en eral ly accep te d m ed ic al m etho do lo gy refe rredto as ‘di ffer en ti al di ag no si s.’ Dr. Suh rb ie r ex pl ai ne d t ha t “ [d ]iffere nt ia l d ia gn os is , or d iff eren ti al eti ol og y , is a st an da rdsci en ti fic tec hn ique of i de nt ifyin g t he cau se of am ed ic al pro bl em by el im in at in g t he li ke ly caus es un ti l t he m os t p ro babl e cau se is is ol at ed .” Dr. Su hrbi er fu rth er s ta te d t ha t i n p erfo rm in g h is di ffer en ti al di ag no si s, h e d et erm in ed th atG.P. di d n otha ve th e Fra gi le X gen et ic di so rd er, “ th e m os t co m m on ‘ kn own ’
cau se of aut is m ,” an d t he refo re co nc lu de d “ [t]hi s m ean s, b as edonou r cu rren t kn owl ed ge , th atth e cau se of h is au ti sm is m os t l ik el y

no t g en et ic in na tu re.” In ad di ti on to th e d iff

eren ti al di ag no si s m etho d, Dr. Su hrbi er al so st at edth athe
so ug hta un ifyin g m ech an is m to ex pl ai n b ot h G.P.’s ASD an d h is syrin go m y el ia
. Acco rd in g t o Dr. Su hrbi er, i t was im po rta ntan d “ co ns is te ntwith g en eral ly
acce pt edm etho do lo gi es withi n t he fie ldof p ed ia tri cs –t o t he ex te ntpo ss ib le –t o lo okforun ifyin g the or ie s o f di ag no si s i n a n e ffo rt t o e xp la ina pr es en ta ti on of sym pt om s.” Dr. Su hrbi er s ta te d t ha t h e was “ qu it e fam il iar with t he co nc ep t t ha t traum a is a reco gn iz edcau se of aut is m an d s yrin go m

y el iain ve ry

y ou ng pa ti en ts .”

7Aga in , Dr. Suh rb ie r pr ov id edno res earc h o r li te ratur e to supp ort t hi s s ta te m en t.

Dr. Suh rb ie r st at ed : “ I co nc lu de d t ha t the m os t l ik el y cau se of [ G.P.] ’s aut is m

an d syrin go m y el iawas t he traum a th athe su st ai ne d i n t ha t m ot orve hi cl e acc id en t i n Apr il of 2 00 2. Itwas, an d s ti ll is , m y op in io n tha t t rau m a was a subs ta nt ia l fa ct or in cau si ng th e d is ab il it ie s t ha t [G.P.] is ex pe rie nc in g t od ay .” Dr. Hoffm anfir stex am in edG.P. onMarc h 2 2, 2 00 6, ap pr ox im at el y fou r y ears aft er the acci de nt . The d is tri ctco urt as se ss edth e ad m is si bi li ty of Dr. Hof fm an ’s tes ti m on y

ba se d o n Dr. Ho ffm an ’s Ind ep en de ntMed ic al Eval ua ti on & Rep ort p rep aredon Decem be r 14 , 20 07 ; a d ep os it io n t ak enby E ve nf lo on Jan ua ry 16 , 20 08 ; an d aSupp le m en ta l Re po rt p rep aredon Ju ne 18 , 20 08
. Inhi s In de pe nd en t Re po rt, Dr. Ho ffm anst at ed : [G.P.] ha s m

ul ti pl e n euro de ve lo pm en ta l i m pa irments th atwil l b e ha nd ic ap pi ng li fel on g. My m ed ic al op in io n, t o areas on ab le de gr ee o f m ed ic al cert ai nt y , is th at[G.P.’ s] m ed ic al co nd it io ns an d ne ur od ev el op m en ta l i m

pa irments (syrin go m

y el ia , aut is m , im

pa ire d ad ap ti ve be ha vi or s) are re la te d a ndsec on dary to th e cl os edhe adan d cen tra l n erv ou s s y st em

in jury he su st ai ne d i n t he [acc id en t] at ag e 2 week s. Inhi s Supp le m en ta l Re po rt, Dr. Ho ffm anpre se nt edten po in ts th athe be li ev es ex pl ai n h ow t he acci de ntcau se d b ot h G.P.’s ASD an d s yrin go m y el ia : Fi rs t, tha t t he bra in , in cl ud in g t he cere be ll um , is act iv el y de ve lo pi ng du rin g t he pe rin at al /n eo na ta l ag e th atth e in jury occu rred . Seco nd , th atth is act iv e b rai n d ev el op m en t p art ic ul arl y in cl ud es de ve lo pi ng 8co nn ect io ns be twee n t he cere be ll um an d d iff eren t re gi on s o f th e co rte x. Th ird , th atab no rm al it ie s i n t he cere be ll um an d i n t he co nn ect io ns be twee n t he cere be ll um an d t he co rte x, ar e st ro ng ly li nk edto au ti sm . Fou rth , th atth e p res en ce o f syrin go hydro m y el ia pr es up po se s ab no rm al cere br al sp in al flu idpre ss ur e aro un d t he cere be ll um

at t he si te of t he ob ex an d fo ram enm ag nu m . Fift h, t ha t ne it he r syrin go hydro m

y el iano r bo rd erl in e Ch ia ri I ab no rm al it ie s were p res en t wh en[G.P.] was a ge 2 wee ks an d wer e certa in ly not pr es en t i n u te ro whenth e ta rg etul tra so un d was pe rfo rm ed . Six th , th athydro m

y el iais alm os t al way s as so ci at edwith h y dr oc ep ha lu s, whi ch [G.P.] ha s n ev er h ad , andDr. Zim m erm an ’s op in io n t ha t [G.P.] do es ha ve hydro m

y el iago es ag ai ns t t he cli ni cal reco rd s i n t hi s ca se an d a ga in stth e acc ep te d kno wled ge ab ou t t he di ffer en ce b etween hyrdo m y el iaan d s yrin go m

y el ia . Sev en th , th atth e p eri na ta l an d ne on at al in te ns iv e car e fo ll ow- up li te ratur e d oe s s up po rt t he as so ci at io n b etween in

jury to the de ve lo pi ng bra in , in cl ud in g traum at ic bra in in

jury, an d l at er o ccu rren ce o f au ti sm sp ect ru m di so rd er. Eig ht h, t ha t [G.P.] di d e xp eri en ce atag e 2 week s . . . en ou gh he adin

jury to caus e, am on g o th er thi ng s, a fo reh eadbru is e, irr it ab il it y , po orfeed in g, re du cedop en in g o f le ft e y e, suba rach no id an d s ub du ral he m orrh ag e, an d s of t t is su e swe ll in g i n t he pa rie to oc ci pi ta l re gi on as we ll as l ik el y hyperfl ex io n n eckin

jury. Nin th , th attak ento ge th er (ra th er tha n i n c oi nc id en ta l, i di op athi c “ wedo n’t-kno w” is ol at io n) th e se qu en ce o f th e in jury to the bra in , sp in al co rd , andsu rro un di ng ti ss ue s atth atti m e th enres ul te d i n c ha ng es to CSF fl ow i n the cerv ic al sp in al co rdan d a ro un d t he for am enm ag nu m wit h s ub se qu en t d ev el op m en t o f syrin go hydro m y el iaan d a ls o re la te d al te redan d i m

pa ire d s ub se qu en t d ev el op m en t o f th e cer eb el lu m an d cere be ll ar co nn ect io ns to th e cer eb ral co rte x re su lt in g i n aut is m sp ect ru m di so rd er . . . Tenth, t he re i s n o e vi de nc e inth e m ed ic al reco rdof a ny spe ci fic ge ne ti c d is or de r as a cau se for[G.P.] ’s aut is m . Dr. Hoff m anfurth er s ta te d tha t G.P.’s au ti sm “ is no t a r es ul t o f ch ro m os om e ab no rm al it y

no r of Frag il e X syndro m e, no r of pe rin at al di st res s o r in su lt , no r of
ne on at al il ln es s. Th ere i s n o s ig n o r ot he r in di cat io n o f pr en at al or p eri na ta l i ns ul t 9orot he r ap paren t et io lo gy for h is au ti sm .” Dr. Hoffm anco nc lu de d: “ G.P.’ s au ti sm

is a di rectres ul t o f th e in

juri es he su st ai ne d t o h is he adan d d ev el op in g b rai n dur in g th e m ot orve hi cl e acc id en t.” Inhi s d ep os it io n, Dr. Ho ffm anst at edth athe ha s n ev er b een in vo lv edin any sc ie nt ifi c stud ie s o n the cau se s o f au ti sm . Whe n a sk edif h e co ul d c it e an y sc ie nt ifi c res earc h t o s up po rt h is op in io n t ha t t rau m at ic bra in in jury or cl os e-h ead in jury caus es au ti sm , Dr. Hoffm anres po nd ed :

I ha ve n’t p ul le d s tu ff fo r th is rep ort d ire ct ly. I ha ve th ou gh t ab ou t t hi s b efo re b ecau se I no te d c li ni cal ly, whi ch is no t wh aty ouare as ki ng , th atwhen I ha ve do ne ne on at al fol lo wup or s een ch il dr enin fo ll owup fr om

bi rth pro bl em s, as part o f m y cli ni cal pra ct ic e th at ha ve au ti st ic featur es , won de rin g i s t he re ev id en ce i n t he li te ratur e li nk in g b rai n i nju ry

or t rau m a to th is . Andso I ha ve do ne so m e li te ratur e se arch es an d t he re ar e rep orts , bo th an im al m od el s an d pe rs on s s ho win g t hi s l in k. . . . I di dn ’t in cl ud e th atin m y rep ort, s o I co ul d fi ndy ouso m e o f th os e. If y ouaskwhatsci en ti fic ba si s, an d wh atI was l oo ki ng forwas am I jus t co m in g up wi th th is m y se lf, o r are th ere o th er p eo pl e se ei ng th is , to o, an d I r eas su redm y se lf t ha t o th er p eo pl e are an d i t’s s ta rti ng to sh ow up i n t he li te ratur e. Ther e is no t, tha t I a m aware o f, li ke a m ajorch ap te r orm ajorart ic le in th e New Eng la ndJo urna l s ay in g t hi s is a pr im ary cau se . Pri orto tri al , th e d is tri ctco urt g ran te d Ev en flo ’s m ot io n t o e xc lu de te st im on y by H en dr ix ’s exp ert s re ga rd in g t he pu rp orte d c au se of G.P.'s ASD. The
co urt re as on edth atth e m etho ds by whi ch Dr. Suh rb ie r an d Dr. Ho ffm anarri ve d a t th e co nc lu si on th atth e acc id en t caus edG.P.’ s ASD were no t s uf fic ie nt ly reli ab le 10un de r Dau be rt . The d is tri ctco urt al so rul edth atit wo uld pe rm itth e ex pe rt te st im on y with re gardto th e cau se of G.P.’s al le ge d s yrin go m y el ia . As a res ul t o f th es e ru li ng s, t he di st ric t co urt g ran te d p art ia l s umm ary jud gm en t t o Ev en flo on Hen dr ix ’s com

pe ns at ory da m ag es cla im

for G.P.’ s ASD, wh il e al lo win g Hen dr ix ’s
co m pe ns at ory da m ag es cla im

forsyrin go m

y el iaan d h er p un it iv e d am ag es cla im to pr oc eedto tri al . Ins te adof p ro ceed in g t o tria l o n h er re m ai ni ng cla im s, Hen dr ix ch os e to vo lu nt ari ly dis m is s wi th pre jud ic e h er re m ai ni ng cla im s an d fi le th is ap pe al
. II. STANDARD OF REVIEW W e rev ie w th e d is tri ctco urt’s ex cl us io n o f ex pe rt t es ti m on y forab us e o f di sc ret io n. Rin k v. Ch emin ov a, In c. , 40 0 F .3d12 86 , 12 91 (11 th Cir . 20 05 ). W e wil l d eferto th e d is tri ctco urt’s ru li ng un le ss itis “ m an ife st ly erron eo us .” Id
.

“ Bec au se th e ta skof e va lu at in g the rel iabi li ty of ex pe rt t es ti m on y is un ique ly
en tru st edto th e d is tri ctco urt . . . we gi ve th e d is tri ctco urt ‘con si de rab le lee way ’ in th e ex ecu ti on of i ts du ty.” Id
. (qu ot in g Ku mho Tir e Co ., Ltd. v. Carmich ae l , 52 6 U.S. 13 7, 1 52 , 11 9 S . Ct. 1 16 7, 1 17 6 (1 99 9) ) (i nt ern al cit at io n o m it te d)
. W e rev ie w th e d is tri ctco urt’s ru li ng on a m ot io n fo r su m m ary jud gm en t de
no vo , app lying th e sa m e le ga l s ta nd ard s t ha t b ou ndth e d is tri ctco urt. Nat ’l Fi re In su r. Co . of

Har tf or d v . For ti ne Co ns t. Co
. , 32 0 F .3d12 60 , 12 67 (11 th Cir . 20 03 ). 11Mo ti on s fo r su m m ary jud gm en t s ho ul d o nl y be gra nt edwhenth e p le ad in gs , de po si ti on s, an swe rs to in te rro ga to rie s, an d a dm is si on s o n fi le , to ge th er wi th th e affi da vi ts , sh ow the re i s n o g enui ne is su e as to an y m at eri al factan d t ha t t he
m ov in g p art y

is en ti tl edto jud gm en t as a m at te r of law. Fed . R. Civ . P. 56 (c); Cel ot ex Co rp . v. Catre tt , 47 7 U.S. 3 17 , 32 2, 1 06 S. Ct. 2 54 8, 2 55 2 (1 98 6)
. III. DISC USSION Hen dr ix rai se s s ev eral is su es onap pe al . Firs t, s he arg ue s t ha t t he di st ric t
co urt erredin fin di ng un rel iabl e u nd er Dau be rt th e ex pe rts ’ te st im on y

th atth e traum at ic bra in in

jury G .P. su st ai ne d i n t he acci de ntcau se d h im to de ve lo p ASD. Prel im in ary to th is arg um en t, Hen dr ix ob jects to th e d is tri ctco urt’s fo cu s o n G.P.’s ASD di ag no si s, ar gu in g t ha t t he co urt s ho ul d i ns te adha ve ass es se d t he ex pe rts ’ te st im on y as i t p ert ai ns to G.P.’ s i nd iv idua l n eu ro lo gi c im pa irments . Seco nd , Hen dr ix arg ue s t ha t the di st ric t co urt erredin ex cl ud in g apo rti on of t he op in io n o f Hen dr ix ’s exp ert , Gary

Whi tm an , rel at in g t o t he lac k o f su ffi ci en t en erg y -ab so rb in g pa dd in g o n t he CRS, t hu s el im in at in g o ne of He nd rix ’s th eo rie s o f de fect iv e pr oduc t. Thi rd , Hend rix arg ue s t ha t t he di st ric t co urt erredin de nyin g h er re qu es t fo r di sc ov ery on a reca ll of Ev en flo saf ety sea ts . Upo n tho ro ug h re vi ew of th e rec or d a ndwith t he be ne fitof o ral arg um en t,
we co nc lu de th atth e d is tri ctco urt d idno t ab us e it s d is cret io n i n e xc lu di ng th e 12ex pe rt t es ti m on y of Dr. Ho ffm anan d Dr. Su hrbi er b as edon th e in su ffi ci en t rel iabi li ty of th attes ti m on y un de r Dau be rt . Becau se witho utth e te st im on y of t ho se two witne ss es su m

m ary jud gm en t was pro pe r on Hend rix ’s com pe ns at ory da m ag es cl ai m forG.P.’ s ASD, an d b ecau se Hend rix vo lu nt ari ly dis m is se d t he rem ai nd er o f he r cl ai m s wi th pre

jud ic e, we do no t re achth e ad di ti on al is su es pre se nt edin th is ap pe al
. 4 A. Ch arac te riz in g G.P.’s Neu ro lo gi c Im pa irments As a p rel im in ary m atte r, we m us t ad dr es s Hen dr ix ’s arg um en t tha t t he di st ric t co urt erredby ask in g wh ethe r th e ex pe rts ha d e st ab li sh edth attraum at ic br ai n i njury

co ul d e ve r cau se ASD. Hendrix arg ue s t ha t, i ns te ad , th e d is tri ctco urt sh ou ldha ve de te rm in edwhet he r tr au m at ic bra in in jury cou ldev er caus e o ne or m or e o f th e in di vi du al ne ur ol og ic de fic it s t ha t l edto G.P.’ s ASD d ia gn os is . As th e ex pe rts in th is cas e te st ifi ed , ASD is a di so rd er tha t i s re co gn iz edan d d ia gn os ed ba se d o n i ts un de rlyin g i m pa irments . The d is tri ctco urt, h owe ve r, di d n otdi sc us s G.P.’ s u nd erl y in g n eu ro lo gi c d efi ci ts sep arat el y . Ins te ad , th e co urt n ot edth at

“ [a]cco rd in g t o Hen dr ix , [G.P.] su ffer s fr om ASD” an d t he n wen t o n t o a na lyze th e

In other wor ds, Hendrix’s second a nd third arguments relate solely to liabilit y , and 4 Evenflo ha s no liabilit y

on Hendr ix ’s claim for

damag es for

G.P.’s ASD. There fore , beca use Hendr ix ’s ASD claim is the sole cla im remainingafte r He ndrix dismiss ed all other claims, Hendr ix ’s sec ond and third ar guments are moot. 13ex pe rts ’ te st im on y in term s o f th atASD di ag no si s g en eral ly. Hen dr ix , 25 5 F .R.D. at57 7. Hen dr ix arg ue s t ha t the di st ric t co urt was requi redto ass es s t he rel iabi li ty of th e ex pe rt t es ti m on y

reg ard in g c au sa ti onof e ach of G.P.’s n eu ro lo gi c im pa irments
. Bec au se ASD is de fin edby its un de rlyin g d efi ci ts an d b eh av io rs , itm ig htbe di ffi cu ltto is ol at e th e d efi ci ts un de rlyin g G.P.’s ASD d ia gn os is an d d et erm in e whe th er trau m at ic bra in in jury cou ldha ve cau se d e ach de fic itin di vi du al ly. Afte r a th or ou gh rev ie w of the reco rd , ho wev er, we co nc lu de th atth e d is tri ctco urt was no t requi redto un de rta ke th atco m pl ic at edtas k b ecau se Hend rix he rs el f fai le d t o fa irl y pr es en t t hi s i ss ue to th e d is tri ctco urt. Hen dr ix ’s exp ert s b ot h re ferr edto G.P.’ s i nd iv idua l d efi ci ts , bu t o pi ne d o nl y th atth ere was a cau sa l l in k b etween traum at ic bra in in jury andG.P.’ s ASD. Neit he r ex pe rt d es cri be d wh ethe r orho w traum at ic bra in in jury cou ldcau se G.P.’ s in di vi du al de fic it s. Fo r ex am pl e, Dr. Hoff

m anrefe rs in pa ss in g t o G.P.’s “ m ul ti pl e ne ur od ev el op m en ta l i m

pa irments ”; ho wev er, i n d es cri bi ng hi s t he ory of h ow t he acci de ntco nt rib ut edto G.P.’ s i nju rie s, Dr. Ho ffm anst at edth e fo ll owi ng : ab no rm al it ie s i n t he cere be ll um , andin th e co nn ect io ns be twee n t he cere be ll um

an d t he co rte x, ar e st ro ng ly lin ke d t o aut is m

. . . th e p eri na ta l an d n eo na ta l i nt en si ve care fol lo w-up l it eratur e d oe s supp ort t he ass oc ia ti on be twee n i nju ry to th e d ev el op in g b rai n, 14in cl ud in g t rau m at ic bra in in jury, an d l at er o ccu rren ce o f au ti sm sp ect ru m di so rd er

. . . th e se qu en ce o f th e in

jury to t he bra in , sp in al co rd , andsu rro un di ng ti ss ue s atth atti m e th enres ul te d i n c ha ng es to CSF fl ow i n t he cerv ic al sp in al co rdan d a ro un d t he for am enm ag nu m with . . . im pa ire d s ub se qu en t d ev el op m en t o f th e cer eb el lu m an d c ereb el la r co nn ect io ns to th e cer eb ral co rte x re su lt in g i n aut is m sp ect ru m di so rd er

. . . th ere i s n o e vi de nc e in th e m ed ic al reco rdof a ny spe ci fic ge ne ti c di so rd er as a cau se for

[G.P.] 's aut is m Thu s, Dr. Ho ffm anap pl ie d h is elabo rat e cau sa ti on th eo ry ex pl ic it ly and
un am bi gu ou sl y to G.P.’ s ASD d ia gn os is ge ne ral ly andno t t o G.P.’s i m pa irments in di vi du al ly. Si m il arl y , Dr. Suh rb ie r no te s G.P.’s u nd erl y in g i m pa irments bu t re fers
ex cl us iv el y

to “ ASD” an d “ au ti sm ” whe n d is cu ss in g c au sa ti on . Dr. Suh rb ie r st at ed du rin g h is de po si ti on th athe ha d d ia gn os edG.P. with au ti sm an d t ha t t he re “ is a hi gh pro babi li ty giv enth e se ve re n atur e o f [G.P.]’ s i nju ry an d h is subs eque nt de ve lo pm en t o f ot he r ne ur ol og ic seq ue la ,” th atth e acc id en t h adcau se d G.P.’s ASD. In h is affi da vi t, Dr. Su hrbi er s ai d h e h ad“ di ag no se d [G.P.] with [a ]uti sm (wh ic h i s o n t he sp ect ru m of [ a]ut is ti c [s ]pect ru m

[d]is or de r),” an d t ha t “ we can reas on ab ly con cl ud e th atitis m or e li ke ly tha n n otth at[G.P.] su ffer edda m ag e to hi s b rai n–pa rti cu la rly the po st eri orreg io ns –wh ic h was , intu rn , a subs ta nt ia l fa ct or

15in cau si ng hi s au ti sm .” Dr. Suh rb ie r al so st at edth at“ [t]rau m a o f va rio us ki nd s i s a

kn own cau se for
. . . au ti sm . . . . as p artof my tre at m en t o f [G.P.], I co nc lu de d t ha t th e m os t l ik el y

cau se of G.P.’s au ti sm

. . . was th e tr au m a th athe su st ai ne d i n t ha t
m ot orve hi cl e acc id en t i n Ap ril of 2 00 2.” Noton ly didHend rix ’s two m ed ic al ex pe rts op in e o nl y ab ou t t he cau se of GP’s ASD di ag no si s t ak enas awho le , Hend rix ’s arg um en ts to th e d is tri ctco urt al so di d n otatt em

ptto pars e th e cau sa ti on is su e wit h re sp ectto an y of GP’s in di vi du al im

pa irments . Accor di ng ly, we can no t co nc lu de th atth e d is tri ctco urt ab us edit s d is cret io n i n fo cu si ng on th e is su e whi ch was fa irl y pre se nt edto it– i .e., th e rel iabi li ty D r. Hoff

m an ’s andDr. Suh rb ie r’s te st im on y th attraum at ic bra in in jury caus edG.P.’ s ASD. Mo reo ve r, in he r in it ia l b rie f be fo re thi s C ou rt, Hen dr ix di d n otarg ue th atitwas app ro pr ia te to foc us on cau sa ti on of G.P.’s n eu ro lo gi c im pa irments sep arat el y . There fo re, we co nc lu de th atsh e h as ab an do ne d thi s arg um en t o n app eal . W e n ow turn t o t he is su e o f whe th er the di st ric t co urt pr op erl y ex cl ud edtes ti m on y

fro m Hend rix ’s exp ert s t ha t t rau m at ic bra in in jury
cau se d G.P.’s ASD. B. Exc lu si on of Ex pe rt Tes ti m on y onCau sa l Li nkBet ween Traum at ic Brai n In jury andASD 1. Leg al Sta nd ard s fo r Adm it ti ng Sci en ti fic Evi de nc e o f Cau sa ti on

16Hen dr ix see ks to adm itex pe rt t es ti m on y th atth e tr aum at ic bra inin jury G .P.
su st ai ne d i n t he acci de ntcau se d h is ASD. Becau se th is is a di ve rs it y cas e, we ap pl y Flo rid a’s subs tant iv e la w reg ard in g apl ai nt iff ’s bu rd enof p ro of

on cau sa ti on . McLeo d v . Am. M ot or s C or p. , 72 3 F .2d83 0, 8 32 (11 th Cir . 19 84 ). Und er Fl or id a la w, Hend rix m ay reco ve r da m ag es up on sh owi ng th atth e tr au m a was a “ subs ta nt ia l fa ct or ” cau si ng G.P.’ s ASD. Gro ss v. Lyo ns , 76 3 S o.2 d 2 76 , 27 9 (Fl a. 20 00 ); Har t v. Ste rn , 82 4 S o.2 d 9 27 , 92 9- 30 (Fl a. 5t h DCA 2 00 2) . A pu rp orte d c au se is a subs ta nt ia l fa ct orif i t o pe rat es in co m bi na ti on with a no th er cau se , su ch as t he ne gl ig en t ac t o f an ot he r orth e p la in ti ff’s p re-e xi st in g p hysic al
co nd it io n, t o c au se anin

jury. Gro ss , 76 3 S o.2 d a t 2 79 ; Har t , 82 4 S o.2 d a t 9 29 -3 0. Alt ho ug h t he st an da rd s fo r fi nd in g c au sa ti on are g ov ern edby Flo rid a la w, we ap pl y fed eral law t o d et erm in e whe th er the ex pe rt t es ti m on y pro ffer edto pro ve cau sa ti on is su ffi ci en tl y

rel iabl e to subm ititto th e jury. Flu ryv. Dai mler Ch rysl er Co rp . , 42 7 F .3d93 9, 9 44 (11 th Cir . 20 05 ) (n ot in g tha t i n d iv ers ity cas es , th e Fed eral Ru le s o f Evi de nc e g ov ern th e ad m is si bi li ty of ev id en ce i n fe de ral co urt). The Fed eral Ru le s o f Evi de nc e p ro vi de : If s ci en ti fic
. . . kn owl ed ge wil l as si stth e tr ie r of factto un de rs ta nd th e ev id en ce o r to de te rm in e a fac t i n i ss ue , a witne ss qu al ifi edas a n ex pe rt b y kn owl ed ge , sk il l, ex pe rie nc e, tr ai ni ng , or e du cat io n, m ay te st ify the ret o i n t he form of a n o pi ni on or o th erwi se , if (1 ) th e te st im on y is ba se d upo n s uf

fic ie ntfact s o r da ta , (2) th e te st im on y is 17th e p ro du ctof r el iabl e p rin ci pl es an d m etho ds , and(3) th e wit ne ss ha s

ap pl ie d t he pri nc ip le s an d m etho ds rel iabl y to th e fac ts of t he cas e. Fed . R. Evi d. 7 02 . “ Unl ik e an ord in ary wit ne ss . . . anex pe rt i s p erm it te d wi de la ti tu de to off

er o pi ni on s, i nc lu di ng th os e th atare n otba se d o n fi rs th an d kn owl ed ge or o bs erv at io n.” Dau be rt , 50 9 U.S. at59 2, 1 13 S. Ct. at27 96 . “ [T]his rel ax at io n o f th e u su al requi rem en t o f fi rs th an d kno wled ge . . . is pre m is edon an as su m pt io n t ha t t he ex pe rt’s o pi ni on wil l h av e a rel iabl e b as is in th e kno wled ge an d e xp eri en ce o f hi s d is ci pl in e.” Id
. A tri al co urt as se ss in g t he rel iabi li ty of an
ex pe rt’s e vi de nc e m

us t t he refo re p erfo rm

a “ ga te ke ep in g” fun ct io n b y co nduc ti ng

“ a p rel im in ary as se ss m en t o f whe th er the reas on in g o r m etho do lo gy un de rlyin g t he te st im on y is sci en ti fic al ly val idan d o f whe th er tha t re as on in g o r m etho do lo gy pr op erl y can be ap pl ie d t o t he fact s i n i ss ue .” Id
. at 5 92 -9 3, 1 13 S. Ct. at27 96 . W e ha ve off ereddi st ric t co urts th e fo ll owi ng ge ne ral gu id an ce i n d et erm in in g wh ethe r to adm itsci en ti fic ev id en ce u nd er Dau be rt : Giv enti m e, in fo rm at io n, an d re so ur ces , cou rts m ay on ly adm itth e st at e o f sc ie nc e as itis . Cou rts are caut io ne d n otto adm itsp ecu la ti on , co njec tu re, o r in fere nc e th atcan no t b e supp orte d b y so un d s ci en ti fic pr in ci pl es . “ The co urtro om is no t t he pl ace f

or sci en ti fic gu es swo rk , ev enof t he in sp ire d s ort. Law la gs sci en ce; itdo es no t l eadit .” Rider v. Sa ndozPha rms . Cor

p. , 29 5 F .3d11 94 , 12 02 (11 th Cir . 20 02 ) (quo ti ng Ros en v. Cib a- Geig

y Co rp . , 78 F.3d31 6, 3 19 (7t h C ir. 1 99 6) ).

18Thi s ci rcu itrequi res tri al co urts act in g a s g at ek eep ers to en ga ge in a

“ rig or ou s t hr ee-p artin qu iry” ass es si ng whet he r: (1 ) th e ex pe rt i s qua li fie d t o t es ti fy co m pe te nt ly regar di ng th e m at te rs he in te nd s t o a ddres s; (2) th e m etho do lo gy by whi ch th e ex pe rt reac he s h is co nc lu si on s i s s uf fic ie nt ly reli ab le as d et erm in edby the so rt o f in qu iry m an da te d i n Dau be rt ; an d (3 ) th e te st im on y ass is ts th e tri er o f fac t, thr ou gh th e ap pl ic at io n o f sc ie nt ifi c, te ch ni cal , or sp eci al iz edex pe rti se , to un de rs ta ndth e ev id en ce o r to de te rm in e a factin is su e. Uni te d Sta tes v. Fr az ie r , 38 7 F .3d12 44 , 12 60 . The p ro po ne ntof t he ex pe rt te st im on y be ars th e b ur de n o f sh owi ng , by a p rep on de ran ce o f th e ev id en ce, tha t th e te st im on y

sat is fie s ea ch pro ng . See Boca Rat on Cmty . Hos p., In c. v. Ten et Hea lth C ar e , 58 2 F .3d12 27 , 12 32 (11 thCir . 20 09 ). Here, the pa rti es rai se no is su es reg ard in g t he fir stan d t hi rdpro ng s. Th eref or e, ou r an al y si s wi ll foc us on whe th er the di st ric t co urt ab us edit s d is cret io n i n e xc lu di ng th e ex pe rt t es ti m on y of Dr. Hoff m anan d Dr. Su hrbi er upo n fi nd in g t ha t t he tes ti m on y was n otsu ffi ci en tl y rel iabl e u nd er Dau be rt . The Dau be rt

Co urt d es cri be d s ev eral fact or s t ria l ju dg es m ay us e to ass es s th e rel iabi li ty of pr of

fere d s ci en ti fic tes ti m on y , in cl ud in g: (1) whet he r th e th eo ry ortec hn ique “ canbe (an d h as be en ) te st ed ,” (2 ) “ whe th er the th eo ry or t ech ni qu e ha s b eensubjec te d t o p eer r ev ie w andpubl ic at io n,” (3) “ in th e cas e o f a p art ic ul ar sc ie nt ifi c te ch ni qu e, . . . the kn own or p ot en ti al rat e o f erro r,” an d (4 ) whe th er the 19th eo ry

or t ech ni qu e is ge ne ral ly accep te d b y th e rel ev an t s ci en ti fic co m m un it y . Dau be rt , 50 9 U.S. at59 2- 94 , 27 86 S. Ct. at27 96 -9 7; se e a ls o Ri nk , 40 0 F .3dat 12 92 (di sc us si ng th es e fac to rs in th e co nt ex t o f as se ss in g a n e xp ert ’s parti cu la r sc ie nt ifi c te ch ni qu e). Thi s l is t, h owe ve r, is no t ex haus ti ve , anddi st ric t co urts

“ ha ve subs ta nt ia l d is cret io n i n d eci di ng ho w to tes t anex pe rt’s re li ab il it y .” Rin k, 40 0 F .3dat 1 29 2. Inad di ti on , th e Supr em e Co urt h as no te d t ha t, i n t he co nt ex t o f th is an al y si s,

“ co nc lu si on s an d m etho do lo gy are no t en ti rel y di st in ctfro m

on e an ot he r.” Gen er al Elec . Co. v. J

oi ne r , 52 2 U.S. 1 36 , 14 6, 1 18 S. Ct. 5 12 , 51 9 (1 99 7) . Alth ou gh
ex pe rts “ co m

m on ly extrap ol at e fro m

ex is ti ng da ta. . . no th in g i n e it he r Dau be rt or th e Fed eral Ru le s o f Evi de nc e requi res a di st ric t co urt t o a dm itop in io n e vi de nc e th atis co nn ect edto ex is ti ng da taon ly by th e ip se di

xi t of t he ex pe rt.” Id
. Rathe r, th e tr ia l co urt i s fr ee t o “ co nc lu de th atth ere i s s im pl y to o g reatanan al yti cal gap be twee n the da taan d t he op in io n p ro ffer ed .” Id
. Hen dr ix ’s exp ert s re ly primaril y on th e d iff

eren ti al eti ol og y

m etho d to li nk

5 Although the parties a

nd other c ases of

ten re fer to this m ethod as “ differ ential 5 diagnosis,” throughout the opinion we will use the more pr ecise term “diff ere ntial etiology .” See McClain v. Me tabolife Int’l, Inc. , 401 F.3d 1233, 1252 ( 11th Cir. 2005) (desc ribingdiffer ential diagnosis and noting that “ [t ]he more pre cise but ra rely used term is diffe rential e tiology”). Diffe rential diagnosis is “the determination of which of two or mor e disea ses with simil ar sy mptoms i s the one fr om which the patient is suffe ring , by a sy stematic compa

rison and contra sting of the clinical finding s.” STEDMAN’ S MEDI CALDI CTI ONARY, 428 (25th e d. 1990). Etiology

ref ers to the “ scienc e and study of the causes of disease and their mode of 20G.P.’ s trau m at ic bra in in jury to h is ASD di ag no si s. Dif fere nt ia l et io lo gy is a
m ed ic al pro ces s o f el im in at io n wh ereb y th e p os si bl e cau se s o f a co nd it io n a re co ns id eredan d ru le d o uton e-b y -o ne , lea vi ng on ly one cau se rem ai ni ng . Se e su pr a n.5 . Hendrix arg ue s t ha t the expe rts ’ op in io ns were re li ab le be cau se di ffer en ti al et io lo gy is a we ll -rec og ni zedsci en ti fic m etho d t ha t h as be enacce pt edby m an y co urts as ava li d b as is forex pe rt t es ti m on y . Se e, e.g . , Best v. Lo we’s Home Cen te rs , Inc
. , 56 3 F .3d17 1, 1 78 -8 4 (6 th Cir . 20 09 ); McCl ai n , 40 1 F .3dat 1 25 2- 53 ; Clau se n v . M/V NewCa riss a , 33 9 F .3d10 49 , 10 57 (9t h C ir. 2 00 3) . W e h av e pr ev io us ly not edth at , when ap pl ie d u nd er ci rcu m st an ces th aten su re re li ab il it y , th e di ffer en ti al eti ol og y

m etho d c anpro vi de a va li d b as is form ed ic al cau sa ti on op in io ns . Se e McCl ai n , 40 1 F .3dat 1 25 2. Here , th e rel iabi li ty of th e m etho d m us t be jud ge d b y

co ns id eri ng th e rea so nabl en es s o f ap pl y in g t he di ffer en ti al eti ol og y ap pr oa chto th e fac ts of thi s ca se an d t he va li di ty of th e ex pe rts ’ parti cu la r m etho d of an al y zi ng th e d at a an d drawi ng co nc lu si on s t he refr om . See Ku mho Tir es , 52 6 U.S. at 1 53 -5 4, 1 19 S. Ct. at11 77 (“ [T]he sp eci fic is su e b efo re the co urt was no t th e rea so nabl en es s in ge ne ra l of ati re ex pe rt' s u se of avi su al an d t act il e in sp ect io n

operation.” Id. at 542 (e mphasis added) . It is undisput ed that G.P. has be en diagnosed with ASD; it is the ca

use of his condition that is at issue. There fore , the re levant methodology used in this case is diffe rential e tiology , i.e., the proc ess of de terminingwhich of two or more c auses is responsible for

the patient’s sy

mptoms. 21to de te rm in e whe th er o ve rd efl ect io n h adcau se d t he ti re's tre adto sep arat e fro m it s st eel -b el te d c arca ss . Rath er, i t was th e rea so nabl en es s o f us in g s uc h an app ro ach , al on g wi th Carl so n's pa rti cu la r m etho d o f an al y zi ng th e d at a th ereb y ob ta in ed , to dr aw a co nc lu si on reg ard in g th e p ar ti cu la r ma tt er to wh ic h the exp er t t es ti mon y wa s dir ect lyrel eva nt .”) (em ph as is in ori gi na l); se e a ls o Qu ie t Te ch . DC-8 v. Hur el

Dub ois UK L TD. , 32 6 F .3d13 33 , 13 43 (11 th Cir . 20 03 ). A rel iabl e d iff

eren ti al eti ol og y

an al y si s i s p erfo rm edintwo st ep s. Fi rs t, the
ex pe rt m us t co m pi le a “ co m

pr eh en si ve li stof h y

po th es es th atm ig htex pl ai n t he set of sal ie ntcli ni cal fin di ng s u nd er co ns id erat io n. . . . The i ss ue at t hi s p oi ntin th e pr oc es s i s wh ic h o f th e co m pe ti ng cau se s ar e ge ne ra ll y cap ab le of c au si ng th e pa ti en t’s s ym

pt om s.” McClai n , 40 1 F .3dat 1 25 3 (q uo ti ng Clau se n v . M/V NEW CARIS SA , 33 9 F .3d10 49 , 10 57 -5 8 (9 th Cir . 20 03 )). Seco nd , th e ex pe rt m us t el im in at e al l caus es bu t o ne . Se e McCu ll oc k v. H.B. Full er Co
. , 61 F.3d10 38 , 10 44 (2dCir . 19 95 ). W it h re ga rdto th e fi rs t s te p, t he di stric t co urt m us t en su re tha t, fo r eac h po ss ib le cau se th e ex pe rt “ ru le s i n” at t he fir stst ag e o f th e an al y si s, t he ex pe rt’s op in io n o n g en eral cau sa ti on is “ de riv edfro m sci en ti fic al ly val idm etho do lo gy.” Hol la nder

v. Sa ndozPha rm. Co rp . , 28 9 F .3d11 93 , 12 11 (10 th Cir . 20 02 ) (quo ti ng Si ha ra th v. Sa nd

ozPha rms . Cor

p. , 13 1 F . Sup p. 2 d 1 34 7, 1 36 2- 63 (N.D. Ga.

2220 01 )). Thi s i s b ecau se “ a fu nd am en ta l as su m pt io n u nd erl y in g [d iff

eren ti al et io lo gy] is th atth e fi na l, s us pe ct ed‘ cau se ’ . . . m us t ac tu al ly be cap ab le of c au si ng th e in jury.” McCl ai n , 40 1 F .3dat 1 25 3. Th us , th e ex pe rts ’ pu rp orte d u se of t he di ffer en ti al eti ol og y

m etho d “ wil l n otov erco m e a fu nd am en ta l fa il ur e to lay the
sc ie nt ifi c g ro un dwo rk ” fo r th e th eo ry th attraum at ic bra in in

jury can, i n g en eral , cau se au ti sm . Se e McCl ai n , 40 1 F .3dat 1 25 2 (“ Thi s ap pr oa ch , ho wev er, wil l n ot
us ua ll y ov erco m e th e fu nd am en ta l fa il ur e o f lay in g asci en ti fic gro un dwo rkforth e ge ne ral to xi ci ty of th e dru g a ndth atitcan cau se th e h arm a pl ai nt iff

su ffer ed .”). So m e sp eci fic pri nc ip le s ar is e in th e co nt ex t o f es tabl is hi ng ge ne ral
cau sa ti on in cas es de al in g wi thm ed ic al in juri es . In McCl ai n , we di st in gu is he d
cas es in whi ch th e m ed ic al co m m un ity ge ne ral ly recog ni zes th ata cert ai n c he m ic al
can cau se th e in

jury the p la in ti ff al le ge s fr om th os e in whi ch th e m ed ic al
co m m un ity ha s n otreac he d s uc h aco ns en su s. 4 01 F.3dat 1 23 9. W e st at edth atin 6 Hendr ix attempts to disti nguish this case fr om McClain on the grounds that ours 6 is an “ordina

ry trauma” case wher eas McClain is a tox ic tort ca se . Although w e ar e not dea ling with a tox ic tort, which is “[a] civil wrongarisingfrom exposure to a toxic substance, such a s asbestos, ra diation, or hazardous wa ste,” B lack’ s L aw Dic tionary (8th ed. 2004), w e ar e dea ling with a medica l injury

alleg edly arisingfrom use of

a def ective product. InMcClain , as in our case , the cour

t was re quired to ana ly

ze expert medical opinions reg ardingthe ca use of a n injury ; thus, the releva

nt inquiry was similar. See M

cClain , 401 F.3d at 1236 (holding that the district court e rrone ously

admitted expert testimony that a we ight- loss supplement caused the plaintiff’s medical pr oblems). B eca use He ndrix has provided no r eason to distinguish be tween the causation evidence in McClain and the instant ca se for the purposes of

the Daubert

analy sis, we conclude that the principles a rticulated in McClain with reg ard to a dmitti ngexpert medical testimony on the ca use of a n injury may properly guide our re liability

inquiry on the ca usation issue. 23th e se co ndcat eg ory of c as es , th e d is tri ctco urt m us t ap pl y th e Dau be rt

an al y si s n ot
on ly to t he expe rt’s m etho do lo gy for fi gu rin g o utwhet he r th e ch em ic al cau se d t he pl ai nt iff’s sp eci

fi c in jury, bu t al so to th e que st io n o f whe th er the dru g o r ch em ic al
can , inge ne ral , cau se th e h arm pl ai nt iff all eg es . Id
. Thu s, t he di stric t co urt m us t
as se ss th e rel iabi li ty of th e ex pe rt’s o pi ni on on ge ne ra l , as wel l as sp eci fic , cau sa ti on . Id
. Hen dr ix do es no t co nt en d t ha t t he m ed ic al co m m un it y ge ne ral ly recog ni zes traum at ic bra in in

jury as a cau se of aut is m . There fo re, the di st ric t co urt was co rrec t to ap pl y th e Dau be rt

an al y si s t o t he qu es ti on of wh ethe r tr au m at ic bra in in jury can, in ge ne ral , cau se au ti sm . W e aff or d the di st ric t co urt s ub st an ti al di sc ret io n t o 7 de ci de ho w to tes t the rel iabi li ty of th e g en eral cau sa ti onev id en ce p res en te d b y Dr. Hof fm anan d Dr. Su hrbi er. Rin k, 40 0 F .3dat 1 29 2. Inrev ie win g t he di st ric t co urt’s re li ab il it y de te rm in at io n, we n ot e th atwe Hendr ix argues that F lorida’s “ substantial fac tor” test absolve s her of establishing 7 g ener al ca

usation betwee n traumatic br ain injury and autism. This argument appea rs to be base d on a misunderstandingthat the “substantial fa ctor” test means that a substantial likelihood of causation is sufficient to impose liabili ty . That is not the case . Florida law’s “ substantial fac tor” require ment is best understood to mean that He ndrix could re cover if a jury found that G.P.’s injuries wer e a pa

rtial or contr ibuting ca

use of his ASD. The district c ourt did not ex clude the expert testimony

on the basis that it did not show that the injury was the onlycause of G.P.’s ASD; rather , the district court found that there w as no scientific ally reliable evidenc e that such brain injuries, in g ener al, could eve r cause autism. Even the “substantial f actor ” test re quires the plaintiff to show a c ausal link based on r eliable e videncebetwee n a purpor ted ca use and the alleg ed injury , as the district cour t require d. Gross , 763 So.2d at 279-80. The district cour t’s failure to expl icitly

articulate Flor ida’s ca

usation standard w as neither prejudicia l nor an a

buse of discretion. 24ha ve pre vi ou sl y id en ti fie d s om e o f th e sc ie nt ifi cal ly val idm etho ds forest ab li sh in g ge ne ral cau sa ti on . For i ns ta nc e, we wil l ad m itex pe rt o pi ni on s p ur su an t t o Dau be rt th atare s up po rte d b y

ep id em io lo gi cal stud ie s, pro vi de d t he ex pe rt e xp la in s h ow 8 th e fi nd in gs of t ho se stud ie s m ay be rel iabl y

co nn ect edto th e fac ts of t he pa rti cu la r cas e. Rider , 29 5 F .3dat 1 19 8 (n ot in g t ha t, al th ou gh th ey are n otm an da to ry ,

“ ep id em io lo gi cal stud ie s m ay be po werfu l ev id en ce o f cau sa ti on ”); se e a ls o , No rr is v. Bax te r Hea lthc ar e Co rp . , 39 7 F .3d87 8, 8 82 (10 th Cir . 20 05 ) (“ [E]pid em io lo gy is th e b es t ev id en ce o f ge ne ral cau sa ti on in a to xi c to rt c as e.”). Anex pe rt’s o pi ni on wil l l ik el y

als o s urvi ve Dau be rt

if t he ex pe rt d es cri be s t he ph y si ol og ic al pro ces s, de riv edby the sci en ti fic m etho d, b y whi cha pa rti cu lar cau se lea ds to th e de ve lo pm en t o f a g iv endi se as e o r syndro m e. McClai n , 40 1 F .3dat 1 25 3 (“ The
un de rlyin g p red ic at es of any caus e-an d- effe ctm ed ic al tes ti m on y are t ha t m ed ic al
sc ie nc e u nd ers ta nd s t he ph y si ol og ic al pro ces s b y whi ch a parti cu la r di se as e o r syndro m e d ev el op s an d kno ws wh atfact or s caus e th e p ro ces s t o o ccu r.”) (quo ti ng Bla ck v. Fo od

Lio n, In c. , 17 1 F .3d30 8, 3 14 (5t h C ir. 1 99 9) ); se e a ls o Da ub er t , 50 9 U.S. at 5 90 , 11 3 S . Ct. at27 95 (no ti ng th atin ord er t o qua li fy as “ sc ie nt ifi c “Epidemiology

is the ‘study

of the distribution and deter minants of health-r elated 8 states and e vents in populations and the application of this study to control of hea lth problems.’” In re TMI Litigation , 193 F.3d 613, 660 n.81 ( 3d Cir. 1999) (quotingFe dera l J udicial Center, Refer ence Manual on Scientific E vidence 174 (1994))
.
25kn owl ed ge ” fo r th e p ur po se s o f Fed . R. Evi d. 7 02 , “ anin fere nc e o r as se rti onm us t be de riv edby the sci en ti fic m etho d” ). Co urts ha ve als o i de nt ifi edot he r m etho ds th at , when us edalo ne , are u nabl e to pro vi de sci en ti fic al ly val idpro of of g en eral cau sa ti on . For i ns ta nc e, in McCl ai n , we ex pl ai ne d t ha t t he “

po st ho c er go pr op te r h oc fal la cy

ass um es cau sa li ty from te m po ral seq ue nc e. . . . It i s ca ll eda fal la cy be cau se itm ak es anass um pt io n b as ed
on th e fal se in fere nc e th ata te m po ral rel at io ns hi p p ro ve s a c au sa l re la ti on sh ip .” McCl ai n , 40 1 F .3dat 1 24 3. Th us , a m ere t em po ral rel at io ns hi p b etween anev en t
an d apa ti en t’s d is eas e o r sym pt om s d oe s n otall ow an ex pe rt t o p la ce tha t ev en t o n a li stof p os si bl e cau se s o f th e d is eas e o r sym pt om s. Ca se stud ie s an d c li ni cal
ex pe rie nc e, us edalo ne an d n otm erel y to bo ls te r ot he r ev id en ce, are als o in su ffi ci en t t o s ho w gen eral cau sa ti on . Se e Rider , 29 5 F .3dat 1 19 9 (“ Alt ho ug h a
co urt m ay rel y on an ecd ot al ev id en ce s uc h a s ca se rep orts . . . co urts m us t co ns id er th atcas e rep orts are m erel y acco un ts of m ed ic al ev en ts . They refl ecton ly repo rte d da ta , no t s ci en ti fic m etho do lo gy.”) (in te rn al cit at io n o m it te d) ; se e a ls o N or ris , 39 7 F.3 d a t 8 87 (“ W e can no t al lo w th e jury to s pe cu la te ba se d o n a n e xp ert ’s op in io n whi chrel ie s o nl y

on cli ni cal ex pe rie nc e in th e ab se nc e o f sh owi ng a co ns is te nt , st at is ti cal ly sig ni fic an t as so ci at io n b etween bre as t i m pl an ts an d s y st em ic di se as e.”). 26Inth e se co ndst ep of t he di ffer en ti al eti ol og y an al y si s, t he ex pe rt m

us t el im in at e al l caus es bu t o ne . Se e McCu ll oc k, 61 F.3dat 1 04 4. Whil e th e fi rs t s te p fo cu se s o n g en eral cau sa ti on , inth e se co ndst ep th e ex pe rt app li es th e fac ts of t he pa ti en t’s ca se to th e li stcrea te d i n t he fir stst ep inord er t o fo rm anop in io n abo ut th e actua l caus e o f th e p at ie nt ’s sym pt om s, i .e., to de te rm in e sp eci fic cau sa ti on . In Clau se n , th e Nin th Cir cu itst at edth atan“ ex pe rt m us t p ro vi de reas on s fo r reject in g al te rn at iv e h y

po th es es us in g s ci en ti fic m etho ds an d p ro cedur es an d the eli m in at io n of th os e h y po th es es m

us t b e fo un de d o n m or e th ansubjec ti ve be li efs or un supp orte d s pe cu la ti on .” 33 9 F .3dat 1 05 8 (i nt ern al qu ot at io n o m it te d) . Thu s,

“ [a] di st ric t co urt i s ju st ifi edin ex cl ud in g e vi de nc e if anex pe rt ‘ut te rly fail s . . . to of fer a n e xp la na ti on forwhy th e p ro ffer edalt ern at iv e cau se ’ was rul edou t.” Id
. (quo ti ng Co op er

v. Smi th &Nep he w, In c. , 25 9 F .3d19 4, 2 02 (4th C ir. 2 00 1) ). W it h t he se pri nc ip le s i n m in d, we n ow re vi ew th e d is tri ctco urt’s de te rm in at io n t ha t t he ex pe rts ’ te st im on y inth is cas e was un rel iabl e u nd er Dau be rt . 2. App li cat io n o f St an da rd s t o Dr. Ho ffm an ’s Test im on y The di stric t co urt d et erm in edth atDr. Hoffm an ’s tes ti m on y reg ard in g ASD
cau sa ti on was i ns uf

fic ie nt ly reli ab le un de r Dau be rt to warran t ad m is si on of t ha t 27te st im on y

at t ria l. The di stric t co urt i de nt ifi ederro rs inDr. Hoffm an ’s di ffer en ti al et io lo gy anal y si s atbo thth e “ ru le in ” an d “ ru le ou t” st ep s. Sp eci fic al ly, th e d is tri ct
co urt d et erm in edth atDr. Hoffm an“ fai l[e d] to sh ow h ow, b y ‘ sc ie nt ifi cal ly val id
m etho do lo gy,’ traum at ic bra in in jury cou ldev er b e a p os si bl e cau se of aut is m in
an y on e.” Hen dr ix , 25 5 F .R.D. at 5 98 . The co urt al so fou ndth atDr. Hoffm an

“ fai le d t o c om

pi le ‘ a co m

pr eh en si ve li st ’ of

all po ss ib le cau se s o f ASD” an d
acco rd in gl y

th at“by fail in g t o i nc lu de all of t he cau se s cu rren tl y th eo riz edin th e m ed ic al li te ratur e in hi s ‘com pr eh en si ve li st ’ of

th e p os si bl e cau se s o f ASD, Hof fm anfai le d t o ‘rul e o ut ’ al l p os si bl e cau se s b uton e.” Hen dr ix , 25 5 F .R.D. at 9

Although the district court stated that the e x pert must make a list of “ all

possible 9 cause s for the c ondition,” Hendrix , 255 F.R.D. at 597, we note that McClain and Clausen mere ly require the list to be “compre hensive.” See McClain , 401 F.3d at 1253; Clausen , 339 F.3d at 1057-58. As the Supre me Court stated in Daubert , “it would be unre asonable to conclude that the subject of sc ientific testimony must be ‘known’ to a

cer tainty ; arguably , there are no cer tainties in science .” 509 U.S. at 590, 113 S. Ct. at 1795 (quoting B rief f or Nicola as Bloe mberg en et al. as Amici Curiae 9). Requiringexperts to compile a list of all possible causes of a patient’s sy

mptoms vi olates this principle. Thus, we think an expert perf orminga differ ential etiolog y

need only

compile a c omprehe nsive list of known cause s in order to adequately

complete the f

irst step of the diffe rential e tiology method. We do not, however , believe the district court’s misstatement of the f irst step of the diffe rential e tiology method led to any error in the cour

t’s overa ll analy sis, in part beca use the c ourt deter

mined that Dr. Hof

fman did not even take into account a ll possibl e ca uses cited in the literature that Dr . Hoffma n himself prese nted. Moreove r, bec ause w e af firm the judg ment of the district cour t only on the basis of its “rulingin” dec ision, even if ther e wa s err or in its “rulingout” dec ision, our holding would not be aff ecte d. There fore , the district court did not abuse its discre tion in finding that Dr. H offman’ s list of ASD causes wa s not comprehe nsive. 2859 7- 98 . W e ag ree wi th th e d is tri ctco urt t ha t Dr. Ho ffm anfai le d t o “ ru le in ”

traum at ic bra in in

jury as a p os si bl e cau se of ASD. Be cau se ou r ho ld in g i n t ha t reg ardis a su ffi ci en t g ro un d upo n wh ic h t he di st ric t co urt ru li ng m ay be affi rm ed , we ne edno t ad dr es s the di st ric t co urt’s d eci si on th atDr. Hoffm anfai le d t o ru le ou t ot he r kn own or p laus ib le cau se s o f ASD. Dr. Hoff m an ’s so le supp ort fo r hi s t he ory th at , inge ne ral , traum at ic bra in in jury can caus e ASD cam e fro m cert ai n m ed ic al tex tb oo ks an d e pi de m io lo gi cal stud ie s s ub m it te d b y

Dr. Hoffm an . The d is tri ctco urt ca refu ll y co ns id eredall of t he
m at eri al s ci te d b y

Hoff m anan d c on cl ud edth at“ no ne of t he se work s co m e cl os e to pr ov id in g u se fu l ev id en ce o f a d efi ni ti ve cau sa l l in k b etween traum at ic he ad 1 0 in juri es an d aut is ti c d is or de rs , andno ne pro vi de ev enm arg in al supp ort fo r 1 1
Hendr ix complains about the district cour t’s use of the w ord “de finitive,” ag ain 1 0 acc using the district court of a dopting a n inflexi ble bright-line standar d of ce rtainty . For the rea sons noted in the prec edingfootnote, we agree that Daubert does not requir e ce rtainty ; it require s only

reliability . Howeve r, despite the district c ourt’s inappropriate choic e of the word “def initive,” the context of the district court’s opinion leave s us confident that the c ourt requir ed no more than r eliability . As the district court sa id in the very same sente nce, D r. Hoff

man’s cited literature provided not eve n “mar g inal support” for his theory

of ca usation. Our own r eview of the cited literature a

mply confirms the la ck of suppor t. Hendr ix objects to the district court’ s rationale, a rguing tha

t medical literature 1 1 provinga ca

usal link betwee n trauma a nd an illness is not a mandatory prer equisite to the admission of opinion testim ony on causation from a qualifie d medical doc tor. In g ener al, we do not require medical doc tors to support their expert opinions with m edica l literature. See Rider , 295 F.3d at 1198 (" It is well-settled that while epide miologica l studies may be powe rful evide nce 29Hof

fm an ’s th eo ry

of arel at io ns hi p b etween ab no rm al [cer eb ral sp in al flu id ] pr es su re an d p ro bl em s wi th cere be ll um pre ss ur e, le ad in g t o aut is m .” Id
. at 6 00 -0 1. W e h av e car efu ll y

an d e xh au st iv el y

rev ie wedth e li te ratur e ci te d b y Dr. Hoffm an an d c on cl ud e th atth e d is tri ctco urt’s co nc lu si on with re gardto each pi ece o f li te ratur e was reas on ab le . W e h ol d t ha t t he di st ric t co urt re as on ab ly con cl ud edth at
no ne of the li te ratur e supp orte d t he rel iabi li ty of Dr. Hoff m an ’s pro ffer ed ph y si ol og ic al pro ces s, an d t ha t n on e o f th e li te ratur e supp orte d Dr. Ho ffm an ’s op in io n t ha t a t rau m at ic bra in in jury lik e GP’s co ul d h av e cau se d o r co nt rib ut edto th e d ev el op m en t o f ASD. Thu s, we co nc lu de th atth e d is tri ctco urt was reas on ab le

of ca usation, the lack the reof

is not fatal to a plaintiff' s case .") . The propone nt of such opinions, howeve r, re tains the burden of offe ringsome proof that the expert’s testimony on g ener al causation is reliable. InRider , for e x ample, we stated: In the abse nce of

epidemiology , plaintiffs may still prove me dical ca

usation by other e vidence . In the instant case , howeve r, plaintiffs simply have not pr ovided reliable evidenc e to support their c onclusions. To admit the plaintiffs' evidenc e, the Court would have to make sever al scientifica lly unsupported “le aps of f

aith” in the causa l chain. The Daubert rule re quires more
. 295 F.3d at 1202. Her e, Dr . Hoffma

n chose to re ly

exclusively

on medical litera

ture to establish g ener al causation between tr aumatic br ain injury and ASD. The ref

ore, the medical literature must provide e noug h support for Dr . Hoffma n’s g ener al ca

usation opinion to satis fy Daubert ’s reliability require ment. See M

cClain , 401 F.3d at 1239-40 (conc luding that e x pert’s opinions on g ener al ca

usation should be excluded beca use the e x pert did not “support his opinions with sufficie nt data or r eliable principles, as identified by the Daubert

rubric . . .” ). 30in de te rm in in g t ha t t he li te ratur e o ve ral l d oe s n otpro vi de th e n eces sa ry supp ort fo r Dr. Hoff m an ’s op in io ns to ren de r th os e o pi ni on s ad m is si bl e u nd er Dau be rt . Rat he r th andupl ic at in g the di st ric t co urt’s p ers ua si ve an al y si s o f th e li te ratur e p ro vi de d b y

Dr. Hoffm an , se e Hen dr ix25 5 F .R.D. at 6 00 -0 3, we wi ll fo cu s o n t ho se pi eces of l it eratur e em ph as iz edby H en dr ix on ap pe al . At or al arg um en t, Hen dr ix ’s cou ns el st at edth atth e m os t co m pe ll in g l it eratur e d is cu ss in g th e p hysio lo gi cal pro ces s b y whi ch traum at ic bra in in jury cou ldcau se au ti sm

is a ch ap te r in a te xtbo oked it edby E ve nf lo ’s m ed ic al ex pe rt Dr. J oe l M or ga n. Se e Gerry A . Ste fan at os & W il so n Q. J oe , Aut is ti c Dis or de r , in Textbo okof C li ni cal Neu ro ps y ch ol og y , 18 5- 26 0 (J oe l E. Mo rg an& Jo se ph H. Rick er, ed s., 2 00 8) . W e readth is ch ap te r car efu ll y an d fa il edto di sc ern an y su gg es ti on th atbra in da m ag e res ul ti ng fro m

po st -b irt h t rau m at ic bra inin jury can caus e au ti sm

sp ect ru m di so rd ers . W e al so saw n o s up po rt f orDr. Hoffm an ’s th eo ry

th atab no rm al cere br al sp in al flu idpre ss ur e inth e cer eb el lu m co ul d c au se ASD. The ch ap te r st at es th at cert ai n l earn in g andm em ory pa tt ern s fo un d i n aut is ti c in di vi du al s h av e b een

“ in te rp ret edas r efl ect io n o f cer eb el la r pa th ol og y ,” bu t al so no te s t ha t “ stud ie s h av e sh own th atfro nt al lo be an d b as al ga ng li a are als o i nv ol ve d” in lea rn in g am em ory , an d t ha t “ [c]on se qu en tl y , th es e fi nd in gs co ul d n otrul e o utanex pl an at io n i n t erm s 31of

a fro nt al -s tri at al dysfunc ti on rathe r th anan om al ie s o f fro nt al -cer eb el lar ci rcu it s.” Id
. at 2 02 . Furt he r on inth e ch ap te r, th e au th or s d is cu ss th e ro le of the cere be ll um in ASD inge ne ral , andno te th at“ hi st ol og ic al stud ie s o f th e au ti st ic bra in ha ve co ns is te nt ly im

pl ic at edreduc ti on of P urki nje ce ll s o f th e cer eb el lu m .” Id
. at 2 21
. The y do no t, h owe ve r, op in e as to whatmig htcau se su cha reduc ti on of t ho se cel ls
. Whi le th es e st at em en ts pro vi de so m e supp ort fo r th e id ea tha t t he cere be ll um is li nk edto au ti sm

in a ve ry ge ne ral sen se , th ey

off er n o re li ab le supp ort fo r Dr. Hof fm an ’s th eo ry

th ata tr au m at ic bra in in

jury lik e th e o ne G.P. su ffer edco ul d
cau se or c on tri bu te to th e d ev el op m en t o f ASD. W e fo un d n o m en ti on at a ll in th e Ch ap te r of

Dr. Hoffm an ’s pro po se d p hysio lo gi cal pro ces s i nv ol vi ng ab no rm al
cere br al sp in al flu idpre ss ur e le ad in g t o ASD. Not ab ly, al th ou gh th e ch ap te r cat al og ue s t he kn owneti ol og ic al fact or s in vo lv edinASD, th e se ct io n t it le d “ Eti ol og ic al co ns id erat io ns ” d oe s n otm en ti on acqui redtraum a in th e p eri na ta l b rai n. Id
. at 2 13 -1 7. Th e se ct io n d is cu ss es ge ne ti c fact or s atlen gt h, an d t he n g oe s o n t o l is t “ ex tri ns ic fact or s” su ch as: vi ru se s; th e pr es en ce o f ot he r ne ur ol og ic al co nd it io ns , su ch as e pi le ps y ; b irt hi ng co m pl ic at io ns ; te rat og en ic subs ta nc es , su ch as c oc ai ne ; an d aut oi m m un e fac to rs . Id
. The s ect io n fai ls to m en ti on traum at ic bra in in jury, an d the au th or s qua li fy ev enth e fac to rs th ey 32do li stby not in g t ha t “ stud ie s d ire ct edto ex am in in g e ti ol og ic fact or s i n [aut is m ]

ha ve su ffer edfro m

li m it at io ns du e to sm al l s am pl e si zes , in ad equa te sp eci fic at io n of di ag no st ic cat eg or ie s, an d s ig ni fic an t h et ero ge ne it y of t he au ti st ic po pu la ti on .” Id
. at 2 17
. Hen dr ix ’s cou ns el als o n ot edas p art ic ul arl y pe rs ua si ve anart ic le ti tl ed La te Neu ro lo gi c a nd

Co gn it iv e S

eq ue la e o f In fl ic te d T ra uma ti c Bra in Inj ur

y in Inf an cy . Barl ow et al
. , La te Neu ro lo gi c a nd Co gn it iv e S

eq ue la e o f In fl ic te d T ra uma ti c Bra in Inj ur

y in Inf an cy , 11 6 P ed ia tri cs , Aug . 20 05 . The art ic le de sc rib es a va rie ty of ne ur ol og ic im

pa irments , in cl ud in g m an y of t he im pa irments fro m

whi ch G.P.
su ffer s, fo un d i n c hi ld renwith i nf li ct edtraum at ic bra in in

jury (e.g., sh ak enbaby syndro m e). Id
. at e 17 4. Whil e Hen dr ix cri ti ci zes th e d is tri ctco urt fo r di sc ou nt in g th e art ic le ba se d o n t he di st in ct io n b etween in fli ct ed(no n- acci de nt al ) an d acci de nt al traum at ic bra in in jury, th e art ic le it se lf s up po rts th e n ot io n t ha t t he two types of i nju rie s ar e d is ti nc t. Fo r in st an ce, the art ic le no te s t ha t m orta li ty rates for in fan ts with i nf

li ct edtraum at ic bra in in

jury are gre at er tha n t ho se forin fan ts who se in juri es were ac ci de nt al
. Id
. at e 17 4. Th e art ic le als o s el f-l im it s i ts fin di ng s b y po in ti ng ou t t he sm al l s am pl e si ze, the ne edfor

furth er s tu dy, andth atth e stud y la ck eda co nt ro l g ro up . Id
. at e 18 4. In fact , th e au th or s m en ti on th atpre vi ou s 33si m il ar s tu di es us edch il dr enwith a n a cci de nt al traum at ic bra in in jury as co nt ro l
subjec ts ag ai ns t wh ic h t o c om pa re tho se subjec ts with i nf li ct edin juri es . Id
. Mo reo ve r, al th ou gh on e p at ie ntin th e stud y de ve lo pe d aut is m

sp ect ru m di so rd er, th e au th or s n ot e th atth e ASD pa ti en t “ m ay ha ve ha d s ig ni fic an t ex po su re t o al co ho l i n u te ro .” Id
. at e 18 3. Th e d is tri ctco urt i de nt ifi edth es e sh ortc om in gs an d
no te d t ha t “ si gn ifi can tl y , no th in g i n t he study pu rp orts to sh ow o r ex pl ai n t he ph y si ol og ic al pro ces s b y

whi ch bra in in

jury pro du ces au ti sm .” Hen dr ix , 25 5 F.R.D. at 6 01 . The co urt t he refo re co nc lu de d t ha t thi s s tu dy was in su ffi ci en t t o supp ort Dr. Ho ffm an ’s ass ert io n t ha t t he li te ratur e supp orts hi s t he ory of c au sa ti on orev ena ge ne ral cau sa l l in k b etween acci de nt al traum at ic bra inin jury andASD. W e can no t s ay

th atth is de te rm in at io n was anab us e o f di sc ret io n. W e fo un d t he m os t d ire ctst at em en t s up po rti ng th e th eo ry th attraum at ic br ai n i njury

can cau se ASD ina te xtbo oksubm it te d b y Dr. Hoffm anth atwas n ot br ou gh t t o o uratt en ti on on ap pe al . Thattex tb oo k s ta te s: Co ns id erab le pre ced en t fo r de le te rio us effe ct s o f va rio us pe rin at al in su lt s o n o rg an iz at io na l ev en ts is pro vi de d b y stud ie s wi th ex pe rimenta l an im al s. In it ia l s tu di es of l at er co rti cal ne ur on al de ve lo pm en t i n “ un da m ag ed ” are as ad jacen t t o i sc he m ic co rti cal in jury in h um anin fan ts sh ow d en dr it ic ab erra ti on s t ha t co ul d co nt rib ut e im

po rta nt ly to s ub se qu en t co gn it iv e d efi ci ts an d e pi le ps y . It i s a c li ni cal tru is m

th atso m e ch il dr enaffe ct edby one or m or e

34pe rin at al in su lt s m ay ex hi bi t n eu ro lo gi cal sequa la e th atare m or e se ve re tha n m ig htbe pre di ct edfro m th e ex te ntof i nju ry

reco gn iz ed by the us ua l b rai n i m ag in g o r ne ur op atho lo gi cal tec hn ique s. Vol pe , Huma n Br ai n Dev el op men t in Neur ol og y of t he Newbo rnat 8 2. In ot he r wor ds , th is tex tb oo k p ro vi de s s om e supp ort fo r th e id ea tha t ev enm in orin juri es su st ai ne d b y

ne wbo rnbra in s ca n re su ltin m or e se ve re n euro lo gi c im pa irments th an on e wou ldex pe ctfro m

th e in it ia l ex te ntof t he in jury. The t ex tb oo k d oe s n ot , ho wev er, l in k s uc h i nju rie s t o ASD, o r pr ov id e an y supp ort fo r Dr. Hoff

m an ’s th eo ry of ASD c au sa ti onin vo lv in g abn orm al cere br al sp in al flu idpre ss ur e. W e are sat is fie d t ha t t he di st ric t co urt d idno t ab us e it s d is cret io n i n co nc lu di ng , bas edon th e li te ratur e Dr. Hoff m anhi m se lf p ro vi de d, t ha t t he re i s n o rel iabl e supp ort fo r Dr. Hoff m an ’s ass ert io n t ha t “pe rin at al an d n eo na ta l i nt en si ve care fol lo w-up l it eratur e d oe s s up po rt t he ass oc ia ti onbe twee n i njury to th e de ve lo pi ng bra in , in cl ud in g trau m at ic bra in in jury, an d l at er o ccurren ce o f au ti sm sp ect ru m di so rd er.” Becau se Dr. Hoffm anoff ers no ot he r sc ie nt ifi cal ly reli ab le 1 2
In addition to concludingfrom our own revie w of the me dical literature that it 1 2 does not support Dr. Hof

fman’s the ory

of ca usation, we a lso note that Dr. Hof fman himself wa s quite qualified in the support he claims from the literature. In his supplemental repor t, he noted that: “Thus, there is a g ener al conse nsus by many in the scientific c ommunity that the etiolog y for a utism spectrum disorders ofte n does include e nvironmental fa ctors, and some rese arc hers have r eporte d specific ally the associa

tion between insults to the perinatal-new born bra in and subsequent deve lopment of autism.” In a similar vein, Dr . Hoffma n testified that he ha d noticed 35ba si s fo r hi s o pi ni on , hi s t es ti m on y is th e type o f “ sp ecu la ti on , con jectu re, o r in fere nc e” tha t we h av e cau ti on eddi st ric t co urts no t t o a dm it
. Rid er , 29 5 F .3dat 12 02
. Hen dr ix att em

pt s t o s id es te p t he de fic ie nc ie s i n the m ed ic al li te ratur e b y fo cu si ng on Dr. Hoffm an ’s exp eri en ce an d t rai ni ng . Merel y de m on st rat in g t ha t an
ex pe rt h as ex pe rie nc e, ho wev er, d oe s n otau to m at ic al ly rend er ev ery op in io n a nd st at em en t b y

th atex pe rt r el iabl e. As an Adv is ory Co m m it te e Not e o n F ed eral Ru le of Evi de nc e 7 02 st at es : If the witne ss is rel y in g s ol el y or p rimaril y

on ex pe rie nc e, th enth e wit ne ss m

us t ex pl ai n h ow t ha t ex pe rie nc e le ad s t o the co nc lu si on reac he d, wh y

th atex pe rie nc e is a su ffi ci en t b as is forth e o pi ni on , and ho w th atex pe rie nc e is rel iabl y ap pl ie d t o t he fact s. Th e tr ia l co urt's ga te ke ep in g fu nc ti on requi res m or e th ansi m pl y “ ta ki ng th e ex pe rt' s wor d fo r it .” Co m m it te e Not es onRu le s - 2 00 0 Am en dm en t (quo ti ng Dau be rt v. Merr el l Do w Pha rms ., Inc
. , 43 F.3d13 11 , 13 19 (9t h C ir. 1 99 5) ). “ Tak in g t he ex pe rt’s wo rdfor in his practice that some children w ith early brain injuries late r deve lop autistic featur es, had wonder ed if other s were seeingthis too, and then “re assure d [hi m] self that other people a re, a nd it’s starting to show up in the literature.” In other wor ds, Dr. Hof fman re fer s both to his own experience and to the literature a s evidenc ing only a tempora l relationship, or a me re c orre lation. Howeve r, we held in McClain that a mer e tempora l relationship, itself, would not ordinarily be sufficie nt to prove a c ausal re lationship. See M cClain , 401 F.3d at 1243 (“Provinga temporal relationship between takingMetabolife a nd the onset of sy

mptoms does not establish a causal relationship.”) 36it ” is pre ci se ly wha t Hen dr ix su gg es ts th e d is tri ctco urt s ho ul d h av e d on e inth is

cas e; ho wev er, we h av e p rev io us ly recog ni zedth at“ ‘[n]oth in g i n e it he r Dau be rt or th e Fed eral Ru le s o f Evi de nc e requi res a di st ric t co urt t o a dm itop in io n e vi de nc e th atis co nn ect edto ex is ti ng da taon ly by th e ip se di

xi t of th e ex pe rt.’” See McCl ai n , 40 1 F .3dat 1 24 4 (q uo ti ng Jo in er , 52 2 U.S. at14 6, 1 18 S. Ct. at51 9 (1 99 7) ). Dr. Hoffm anha s n otpro vi de d arel iabl e b as is , der iv edby the sci en ti fic
m etho d, fo r co nc lu di ng th attraum at ic bra inin jury can caus e ASD. W e d ecl in e to
co nc lu de th atth e d is tri ctco urt ab us edit s d is cret io n i n fa il in g t o a dm itDr. Hof fm an ’s tes ti m on y

ba se d o n h is expe rie nc e al on e. Bec au se th e m ed ic al li te ratur e ad du cedby H en dr ix supp orts ne it he r Dr. Hof fm an ’s th eo ry

of c au sa ti on in vo lv in g abn orm al cere br al sp in al flu idpre ss ur e no r hi s u lt im at e o pi ni on th ata tr au m at ic bra inin jury lik e GP’s can cau se au ti sm , an d b ecau se Dr. Hoffm anoff ers no ot he r sc ie nt ifi cal ly reli ab le ba si s fo r hi s op in io n, we ho ldth atth e d is tri ctco urt d idno t ab us e it s d is cret io n i n c on cl ud in g

1 3

For example, there is no evide nce that Dr. Hoff man’s theor

y of ca usation has bee n 1 3 tested or subjec t to peer- revie wed publication. See Daubert , 509 U.S. at 593-94; 2786 S. Ct. at 2796-97. And, other

than Dr. H offman’ s own unsupported a nd qualified a ssertion of g ener al acc eptanc e in the scie ntific community , there is no evidence that Dr. Hof fman’s the ory

is g ener ally acc epted in the r eleva

nt scientific community
. See McClain , 401 F.3d at 1244 (with respe ct to the ipse dixit

of an e x pert). 37th atHend rix fai le d t o e st ab li sh ge ne ral cau sa ti on to supp ort Dr. Ho ffm an ’s

op in io n. Th atis , Hend rix ha s fa il edrel iabl y to “ru le in ” tr au m at ic bra in in juri es li ke GP’s as apl au si bl e cau se of aut is m . Bec au se th is is a su ffi ci en t b as is on whi ch to affi rm th e d is tri ctco urt’s ru li ng ex cl ud in g Dr. Ho ffm an ’s tes ti m on y , we nee d n otad dr es s the di st ric t co urt’s de ci si on th atDr. Hoffm anals o fa il edto “ru le ou t” ot he r po ss ib le cau se s. Th e di st ric t co urt h el d: Hof fm an ’s cla im

th athe rul edou t g en et ic s as a po te nt ia l caus e o f [GP’s] ASD ba se d o n [GP ’s] no rm al “ Frag il e X” te st s i gn or es th e po ss ib il it y

of o th er g en et ic co nd it io ns as acau se . Giv enth e p le th or a of ge ne ti c th eo rie s fo r au ti sm , “ ru li ng ou t” Frag il e X as a po ss ib le cau se of [ GP’s] ASD far fr om eli m in at es all ge ne ti c cau se s o f hi s ASD, letalo ne th e o th er m ul ti tu de of f

act or s t ha t h av e b een li nk edto au ti sm or ASD. Hen dr ix , 25 5 F .R.D. at 5 98 (fo ot no te s o m it te d) . The m ed ic al li te ratur e in di cat es th atth ere are a d iz zy in g a rray of o th er fac to rs th atha ve be enm en ti on edas p os si bl e cau se s, i nc lu di ng as m an y as 9 0 g en e m

ut at io ns th atco ul d p la y

a ro le in th e de ve lo pm en t o f au ti sm . Se e Fran k P ol le au x & GeanM. Lau de r, To wa rd a Devel op men ta l Ne ur ob io lo gyof Aut is m, 10 Men ta l Re ta rd at io n a ndDev. Dis ab il it ie s R es earc h R ev . 30 3, 3 09 , 31 0- 12 (20 04 ). Dr. Hoffm anco nc ed edin hi s de po si ti on tes ti m on y

th at , un le ss on e o f th e g en et ic ch ro m os om e an om al ie s t ha t i s

38kn own to cau se au ti sm is id en ti fie d, m ed ic al sci en ce s im pl y do es no t kno w what
cau se s au ti sm . Obv io us ly, in su ch a si tu at io n, t he tas k o f “ ru li ng ou t” ot he r pl au si bl e cau se s i s ex tre m el y co m pl ex . In l ig htof o ur

de ci si on th atDr. Hoffm an fai le d t o re li ab ly “ru le in ” h is th eo ry of ASD c au sa ti on , we nee d n otin th is cas e ve ntur e in to th e qua gm ire of a tt em pt in g t o d efi ne th e p aram et ers of arel iabl e pr oc es s o f “ ru li ng ou t” ot he r po ss ib le cau se s o f au ti sm . 3. App li cat io n o f St an da rd s t o Dr. Su hrbi er’s Tes ti m on y Hen dr ix als o o bjec ts to th e d is tri ctco urt’s ex cl us io n o f Dr. Su hrbi er’s te st im on y . Dr. Suh rb ie r, G.P.’ s t reat in g p hysic ia n, s ou gh t t o t es ti fy as a n e xp ert wit ne ss un de r Ru le 70 2. In ord er t o b e ad m it te d i nt o e vi de nc e, Dr. Su hr bi er’s op in io ns m

us t al so be ba se d o n asci en ti fic al ly reli ab le m etho do lo gy un de r Dau be rt . Se e Uni te d Sta tes v. Hen de rs on , 40 9 F .3d12 93 , 12 99 -1 30 0 (1 1t h C ir. 20 05 ). Dr. Suh rb ie r pu rp orte d t o b ot h p erfo rm a di ffer en ti al eti ol og y

an d t o l oo k fo r a u ni fy in g the ory

to ex pl ai n G.P.’s ASD an d s yrin go m y el ia . Like Dr. Hoffm an , he
co nc lu de d t ha t the “ m os t l ik el y cau se of [ G.P.] ’s aut is m

an d s yrin go m

y el iawas t he traum a th athe su st ai ne d i n t ha t m ot orve hi cl e acc id en t i n Ap ril of 2 00 2.” Unl ik e Dr. Hoff m an , ho wev er, Dr. Su hrbi er d idno t ev enatt em ptto pro vi de an y

ev id en ce 39to supp ort a g en eral cau sa l l in k b etween traum at ic bra in in jury andASD. He pr es en te d n o m ed ic al li te ratur e, de sc rib edno rel ev an t p hysio lo gi cal pro ces s, an d pr ov id edno ot he r supp ort fo r hi s co nc lu si on th attraum at ic bra in in jury can caus e au ti sm . Bas edon th e Dau be rt requi rem en ts for

adm it ti ng ex pe rt t es ti m on y , we can no t s ay

th atth e d is tri ctco urt ab us edit s d is cret io n i n d et erm in in g t ha t t he re was to o g reatanan al yti cal gap b etween Dr. Suh rb ie r’s ev id en ce an d c on cl us io ns reg ard in g G.P.’s ASD d ia gn os is to subm itth os e co nc lu si on s t o the jury. 1 4 IV. CONCLUSION Und er Dau be rt , itis th e u ni qu e ro le of t he di stric t co urt t o d et erm in e whe th er anex pe rt’s o pi ni onis su ffi ci en tl y rel iabl e to all ow i t t o b e p res en te d t o ajury. Here, the di st ric t co urt co nc lu de d t ha t Hen dr ix fai le d t o p res en t s ci en ti fic al ly rel iabl e ev id en ce tha t t rau m at ic bra in in jury can ev er caus e au ti sm . Thu s, t he

Hendr ix also argues that the e x pert testimony of Dr. H offman a

nd Dr. Suhrbier

is 1 4 reliable beca

use both soug ht to find a “unify ing me chanism” e x plaining both G.P.’s ASD a nd sy ring omy elia. B oth doctors came to the conc lusion that the unifying me chanism wa s the traumatic br ain injury

G.P. sustained in the acc ident. This argument fails for the same re ason Hendr ix ’s ar gument related to differ ential etiolog y fails. Ther e is no evidenc e that is scientifica lly

reliable under Daubert

indicatingthat traumatic br ain injury can e ver c ause or contribute to ASD. Ther efor e, it follows that there is no scientifically reliable evidenc e that traumatic br ain injury

can c ause or

contribute to both ASD and sy ring omy elia. More over, reg ardle ss of the ra

rity of either condition or the proba

bility that both conditions would be prese nt in the same individual, Hendrix’s experts have provide d no support for the notion that the acc ident is a more likely

unifying me chanism than some other common cause . 40di st ric t co urt ex cl ud edth e ex pe rts ’ th eo rie s b ecau se of alac k o f rel iabl e p ro of of ge ne ral cau sa ti on be twee n t he all eg edin jury andth e p ur

po rte d c au se of t ha t in jury. Upo n t ho ro ug h re vi ew of th e rec or d a ndwith t he be ne fitof o ral arg um en t, 1 5
we co nc lu de th atth e d is tri ctco urt p ro pe rly exec ut edit s g at ek eep er fu nc ti on un de r Dau be rt , andth eref

or e th e co urt d idno t ab us e it s d is cret io n i n e xc lu di ng th e ex pe rt te st im on y . W e em ph as iz e th atwe ex pr es s n o o pi ni on reg ard in g wh ethe r tr au m at ic bra in in jury sus ta in edin th e p eri na ta l o r ne on at al pe rio d c anev er caus e o r co nt rib ut e to la te r de ve lo pm en t o f anau ti sm sp ect ru m di so rd er. Rat he r, as we ha ve pre vi ou sl y st at ed : “ The co urtro om

is no t t he pl ace f

orsci en ti fic gu es swo rk , eve n o f th e in sp ire d s ort. Law la gs sci en ce; itdo es no t l eadit .” Rider , 29 5 F .3dat 1 20 2 (quo ti ng Ros en , 78 F.3dat 3 19 ). W e em ph as iz e al so th atou r co nc lu si on , andth at of th e d is tri ctco urt, i s b as edon ly on t he ev id en ce p res en te d i n thi s ca se . Giv enth e cu rren t s ta te of s ci en ti fic kn owl ed ge reg ard in g t he cau se s o f au ti sm sp ectru m di so rd ers (as itha s b een pre se nt edto us by the pa rti es ), we are u nabl e to say tha t th e d is tri ctco urt ab us edit s d is cret io n i n e xc lu di ng th is ex pe rt t es ti m on y . Becau se

We can r ejec t summarily

Hendr ix ’s ar gument that the testimony of Evenf lo’s 1 5 experts constituted reliable e vidence of such g ener al ca usation. 41wit ho utth is tes ti m on y th ere i s n o g enui ne di sp ut e o f m at eri al factreg ard in g cau sa ti on of G.P.’s ASD, th e d is tri ctco urt’s g ran t o f su m m ary jud gm en t o n Hen dr ix ’s so le rem ai ni ng cla im was app ro pr ia te . Acco rd in gl y , th e d is tri ctco urt’s ex cl us io n o f ex pe rt t es ti m on y an d g ran t o f
su m m ary jud gm en t ar e AFFIR MED.

42