Document ID: ./input/supremecourt_opinions/opinions/12pdf/11-1425_cb8e.pdf
Page Number: 17.0

Cite as:  569 U. S. ____ (2013) 

13 

Opinion of the Court 
Opinion of SOTOMAYOR, J. 

relatively predictably.6 

Of  course,  there  are  important  countervailing  concerns. 
While  experts  can  work  backwards  from  the  BAC  at  the
time  the  sample  was  taken  to  determine  the  BAC  at  the
time  of  the  alleged  offense,  longer  intervals  may  raise 
questions  about  the  accuracy  of  the  calculation.    For  that 
reason,  exigent  circumstances  justifying  a  warrantless
blood  sample  may  arise  in  the  regular  course  of  law  en­
forcement  due  to  delays  from  the  warrant  application 
process.  But  adopting  the  State’s  per se  approach  would
improperly  ignore  the  current  and  future  technological
developments  in  warrant  procedures,  and  might  well 
diminish the incentive for jurisdictions “to pursue progres­
sive  approaches  to  warrant  acquisition  that  preserve  the
protections  afforded  by  the  warrant  while  meeting  the
legitimate  interests  of  law  enforcement.”  State  v.  Rodri-
guez, 2007 UT 15, ¶46, 156 P. 3d 771, 779.

In short, while the natural dissipation of alcohol in the
blood may support a finding of exigency in a specific case, 
as  it  did  in  Schmerber,  it  does  not  do  so  categorically.
Whether  a  warrantless  blood  test  of  a  drunk-driving  sus­
pect is reasonable must be determined case by case based 
on the totality of the circumstances. 

C 
In an opinion concurring in part and dissenting in part, 
THE CHIEF JUSTICE agrees that the State’s proposed per se
rule  is  overbroad  because  “[f]or  exigent  circumstances  to 
—————— 

6 The  dissent  claims  that  a  “50-state  survey  [is]  irrelevant  to  the  ac
tual disposition of this case” because Missouri requires written warrant 
applications.    Post,  at  8.  But  the  per se  exigency  rule  that  the  State
seeks  and  the  dissent  embraces  would  apply  nationally  because  it 
treats  “the  body’s  natural  metabolization  of  alcohol”  as  a  sufficient 
basis for a warrantless search everywhere and always.  Post, at 1.  The 
technological  innovations  in  warrant  procedures  that  many  States 
have  adopted  are  accordingly  relevant  to  show  that  the  per se  rule  is 
overbroad. 

 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
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