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Page Number: 9

6 

SMITH v. ARIZONA 

Opinion of the Court 

But the Illinois Supreme Court rejected Williams’s claim, 
holding  that  Lambatos’s  testimony  about  the  private  lab
analyst’s finding did not raise a Confrontation Clause issue.
See People v. Williams, 238 Ill. 2d 125, 143–144, 939 N. E. 
2d  268,  278–279  (2010).    The  court  explained  that  under
state evidence law, an expert can disclose “underlying facts
and data” for “the purpose of explaining the basis for [her] 
opinion.”  Id.,  at  137,  143,  939  N. E.  2d,  at  274–275,  278. 
And when she does so, the court held, the testimony is not 
subject to the Confrontation Clause because it is not admit-
ted “for the truth of the matter asserted.”  Id., at 143, 939 
N. E. 2d, at 278.  Thus, Lambatos could relay the private 
lab’s finding that L. J.’s vaginal swabs produced a certain
DNA profile in order to “explain[ ] the basis for her opinion” 
that  “there  was  a  DNA  match  between  [Williams’s]  blood 
sample and the semen sample recovered from L. J.”  Id., at 
150, 939 N. E. 2d, at 282.  The admission of the private lab 
report’s contents for that “limited purpose,” the court rea-
soned, would “aid the [factfinder] in assessing the value of
[Lambatos’s] opinion.”  Id., at 144, 939 N. E. 2d, at 278; see 
id., at 150, 939 N. E. 2d, at 282. 

This Court granted Williams’s petition for certiorari, but 
failed to produce a majority opinion.  Four Members of the 
Court  approved  the  Illinois  Supreme  Court’s  approach  to
“basis evidence,” and agreed that Lambatos’s recitation of
the private lab’s findings served “the legitimate nonhearsay
purpose of illuminating the expert’s thought process.”  Wil-
liams, 567 U. S., at 78 (plurality opinion).  But the remain-
ing five Members rejected that view.  Those five stated, in 
two opinions, that basis evidence is generally introduced for 
its  truth,  and  was  so  introduced  at  Williams’s  trial. 
JUSTICE  THOMAS  explained  that  “the  purportedly  limited 
reason  for  [the  basis]  testimony—to  aid  the  factfinder  in
evaluating  the  expert’s  opinion—necessarily  entail[ed]  an 
evaluation of whether [that] testimony [was] true”: “[T]he 
validity  of  Lambatos’[s]  opinion  ultimately  turned  on  the