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MISSOURI v. MCNEELY 

Syllabus 

not constitute an exigency in every case sufficient to justify conduct-
ing a blood test without a warrant.  Pp. 4–13, 20–23.

(a) The principle that a warrantless search of the person is reason-
able  only  if  it  falls  within  a  recognized  exception,  see,  e.g.,  United 
States v. Robinson, 414 U. S. 218, 224, applies here, where the search
involved a compelled physical intrusion beneath McNeely’s skin and 
into his veins to obtain a blood sample to use as evidence in a crimi-
nal investigation.  One recognized exception “applies when ‘ “the exi-
gencies of the situation” make the needs of law enforcement so com-
pelling  that  [a]  warrantless  search  is  objectively  reasonable.’ ” 
Kentucky v. King, 563 U. S. ___, ___.  This Court looks to the totality 
of  circumstances  in  determining  whether  an  exigency  exits.    See 
Brigham City v. Stuart, 547 U. S. 398, 406.  Applying this approach 
in Schmerber, the Court found a warrantless blood test reasonable af-
ter  considering  all  of  the  facts  and  circumstances  of  that  case  and 
carefully basing its holding on those specific facts, including that al-
cohol levels decline after drinking stops and that testing was delayed
while officers transported the injured suspect to the hospital and in-
vestigated the accident scene.  Pp. 4–8.

(b) The  State  nonetheless  seeks  a  per se  rule,  contending  that  exi-
gent  circumstances  necessarily  exist  when  an  officer  has  probable 
cause to believe a person has been driving under the influence of al-
cohol because BAC evidence is inherently evanescent.  Though a per-
son’s  blood  alcohol  level  declines  until  the  alcohol  is  eliminated,  it 
does  not  follow  that  the  Court  should  depart  from  careful  case-by-
case assessment of exigency.  When officers in drunk-driving investi-
gations can reasonably obtain a warrant before having a blood  sam-
ple  drawn  without  significantly  undermining  the  efficacy  of  the 
search,  the  Fourth  Amendment  mandates  that  they  do  so.    See 
McDonald v. United States, 335 U. S. 451, 456.  Circumstances may
make obtaining a warrant impractical such that the alcohol’s dissipa-
tion will support an exigency, but that is a reason to decide each case 
on its facts, as in Schmerber, not to accept the “considerable overgen-
eralization”  that  a  per se  rule  would  reflect,  Richards  v.  Wisconsin, 
520 U. S. 385, 393.  Blood testing is different in critical respects from
other destruction-of-evidence cases.  Unlike a situation where, e.g., a 
suspect has control over easily disposable evidence, see Cupp v. Mur-
phy, 412 U. S. 291, 296, BAC evidence naturally dissipates in a grad-
ual and relatively predictable manner.  Moreover, because an officer 
must typically take a DWI suspect to a medical facility and obtain a
trained  medical  professional’s  assistance  before  having  a  blood  test
conducted, some delay between the time of the arrest or accident and
time  of  the  test  is  inevitable  regardless  of  whether  a  warrant  is  ob-
tained.  The  State’s  rule  also  fails  to  account  for  advances  in  the  47