Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-402_h315.pdf
Page Number: 26

22 

CARPENTER v. UNITED STATES 

Opinion of the Court 

threatened with imminent harm, or prevent the imminent
destruction of evidence.  563 U. S., at 460, and n. 3. 

As  a  result,  if  law  enforcement  is  confronted  with  an 
urgent  situation,  such  fact-specific  threats  will  likely 
justify  the  warrantless  collection  of  CSLI.    Lower  courts, 
for  instance,  have  approved  warrantless  searches  related 
to  bomb  threats,  active  shootings,  and  child  abductions. 
Our  decision  today  does  not  call  into  doubt  warrantless 
access  to  CSLI  in  such  circumstances.    While police  must
get a warrant when collecting CSLI to assist in the mine-
run  criminal  investigation,  the  rule  we  set  forth  does  not
limit their ability to respond to an ongoing emergency. 

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As Justice Brandeis explained in his famous dissent, the 
Court  is  obligated—as  “[s]ubtler  and  more  far-reaching
means  of  invading  privacy  have  become  available  to  the 
Government”—to  ensure  that  the  “progress  of  science”
does not erode Fourth Amendment protections.  Olmstead 
v. United States, 277 U. S. 438, 473–474 (1928).  Here the 
progress of science has afforded law enforcement a power-
ful new tool to carry out its important responsibilities.  At 
the  same  time,  this  tool  risks  Government  encroachment 
of  the  sort  the  Framers,  “after  consulting  the  lessons  of
history,”  drafted  the  Fourth  Amendment  to  prevent.    Di 
Re, 332 U. S., at 595. 

We  decline  to  grant  the  state  unrestricted  access  to  a 
wireless  carrier’s  database  of  physical  location  infor-
mation.  In  light  of  the  deeply  revealing  nature  of  CSLI,
its  depth,  breadth,  and  comprehensive  reach,  and  the 
inescapable and automatic nature of its collection, the fact
that such information is gathered by a third party does not 
make  it  any  less  deserving  of  Fourth  Amendment  protec-
tion.  The Government’s acquisition of the cell-site records
here was a search under that Amendment. 

The  judgment  of  the  Court  of  Appeals  is  reversed,  and