Document ID: ./input/supremecourt_opinions/opinions/23pdf/22-899_97be.pdf
Page Number: 12.0

Cite as:  602 U. S. ____ (2024) 

9 

Opinion of the Court 

methamphetamine,” three “[c]ontained a usable quantity of
marijuana,” and one “[c]ontained a usable quantity of can-
nabis.”  Id., at 86a–87a.  The State originally planned for 
Rast to testify about those matters at Smith’s trial. 

But with three weeks to go, the State called an audible, 
replacing  Rast  with  a  different  DPS  analyst  as  its  expert 
witness.  In  the  time  between  testing  and  trial,  Rast  had 
stopped working at the lab, for unexplained reasons.  And 
the State chose not to rely on the now-former employee as
a witness.  So the prosecutors filed an amendment to their 
“final pre-trial conference statement” striking out the name
Elizabeth Rast and adding “Greggory Longoni, forensic sci-
entist  (substitute  expert).”    Id.,  at  26a.  Longoni  had  no 
prior  connection  to  the  Smith  case,  and  the  State  did  not
claim  otherwise.  Its  amendment  simply  stated  that  “Mr. 
Longoni  will  provide  an  independent  opinion  on  the  drug 
testing performed by Elizabeth Rast.”  Ibid.  And it contin-
ued: “Ms. Rast will not be called.  [Mr. Longoni] is expected 
to have the same conclusion.”  Ibid. 

And  he  did  come  to  the  same  conclusion,  in reliance  on 
Rast’s  records.    Because  he  had  not  participated  in  the
Smith case, Longoni prepared for trial by reviewing Rast’s
report and notes.  And when Longoni took the stand, he re-
ferred  to  those  materials  and  related  what  was  in  them, 
item by item by item.  As to each, he described the specific 
“scientific  method[s]”  Rast  had  used  to  analyze  the  sub-
stance  (e.g.,  a  microscopic  examination,  a  chemical  color 
test, a gas chromatograph/mass spectrometer test).  Id., at 
41a; see id., at 42a, 46a–48a.  And as to each, he stated that 
the  testing  had  adhered  to  “general  principles  of  chemis-
try,” as well as to the lab’s “policies and practices,” id., at 
47a–48a; see id., at 40a; so he noted, for example, that Rast
had  run  a  “blank”  to  confirm  that  testing  equipment  was
not  contaminated,  id.,  at  42a,  47a.    After  thus  telling  the
jury what Rast’s records conveyed about her testing of the
items,  Longoni  offered  an  “independent  opinion”  of  their