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Page Number: 13

10 

SMITH v. ARIZONA 

Opinion of the Court 

identity.  Id., at 46a–47a, 49a.  More specifically, the opin-
ions he offered were: that Item 26 was “a usable quantity of 
marijuana,”  that  Items  20A  and  20B  were  “usable  quan-
tit[ies] of methamphetamine,” and that Item 28 was “[a] us-
able quantity of cannabis.”  Ibid. 

After Smith was convicted, he brought an appeal focusing 
on Longoni’s testimony.  In Smith’s view, the State’s use of 
a  “substitute  expert”—who  had  not  participated  in  any  of
the  relevant  testing—violated  his  Confrontation  Clause
rights.  Id., at 26a; see Brief for Appellant Smith in No. 1
CA–CR 21–0451 (Ariz. Ct. App.), pp. 20–23.  The real wit-
ness against him, Smith urged, was Rast, through her writ-
ten statements; but he had not had the opportunity to cross-
examine her.  See ibid.  The State disagreed.  In its view, 
Longoni  testified  about  “his  own  independent  opinions,” 
even though making use of Rast’s records.  Brief for Appel-
lee Arizona in No. 1 CA–CR 21–0451 (Ariz. Ct. App.), p. 22. 
So Longoni was the only witness Smith had a right to con-
front.  See ibid. 

The  Arizona  Court  of  Appeals  affirmed  Smith’s  convic-
tions, rejecting his Confrontation Clause challenge.  It re-
lied on Arizona precedent (similar to the Illinois Supreme
Court’s  decision  in  Williams)  stating  that  an  expert  may 
testify to “the substance of a non-testifying expert’s analy-
sis, if such evidence forms the basis of the [testifying] ex-
pert’s  opinion.”    App.  to  Pet.  for  Cert.  11a–12a  (quoting 
State  ex rel.  Montgomery  v.  Karp,  236  Ariz.  120,  124,  336 
P. 3d 753, 757 (App. 2014)).  That is because, the Arizona 
courts have said, the “underlying facts” are then “used only
to show the basis of [the in-court witness’s] opinion and not 
to prove their truth.”  Ibid., 336 P. 3d, at 757.  On that view, 
the  Court  of  Appeals  held,  Longoni  could  constitutionally
“present[ ]  his  independent  expert  opinions”  as  “based  on
his review of Rast’s work.”  App. to Pet. for Cert. 11a. 

We  granted  certiorari  to  consider  that  reasoning,  600