Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-402_h315.pdf
Page Number: 21

Cite as:  585 U. S. ____ (2018) 

17 

Opinion of the Court 

moment,  over  several  years.    Such  a  chronicle  implicates
privacy concerns far beyond those considered in Smith and 
Miller. 

Neither does the second rationale underlying the third-
party  doctrine—voluntary  exposure—hold  up  when  it
comes  to  CSLI.  Cell  phone  location  information  is  not 
truly “shared” as one normally understands  the term.  In 
the  first  place,  cell  phones  and  the  services  they  provide
are “such a pervasive and insistent part of daily life” that
carrying  one  is  indispensable  to  participation  in  modern
society.  Riley, 573 U. S., at ___ (slip op., at 9).  Second, a 
cell  phone  logs  a  cell-site  record  by  dint  of  its  operation,
without any affirmative act on the part of the user beyond
powering  up.    Virtually  any  activity  on  the  phone  gener-
ates  CSLI,  including  incoming  calls,  texts,  or  e-mails  and 
countless  other  data  connections  that  a  phone  automati-
cally  makes  when  checking  for  news,  weather,  or  social
media updates.  Apart from disconnecting the phone from
the  network,  there  is  no  way  to  avoid  leaving  behind  a 
trail of location data.  As a result, in no meaningful sense 
does  the  user  voluntarily  “assume[ ]  the  risk”  of  turning
over  a  comprehensive  dossier  of  his  physical  movements. 
Smith, 442 U. S., at 745. 

We  therefore  decline  to  extend Smith  and  Miller  to  the 
collection of CSLI.  Given the unique nature of cell phone
location  information,  the  fact  that  the  Government  ob-
tained  the  information  from  a  third  party  does  not  over-
come Carpenter’s claim to Fourth Amendment protection. 
The Government’s acquisition of the cell-site records was a 
search within the meaning of the Fourth Amendment. 

* 

* 
Our decision today is a narrow one.  We do not express a
view  on  matters  not  before  us:  real-time  CSLI  or  “tower 
dumps” (a download of information on all the devices that 
connected  to  a  particular  cell  site  during  a  particular 

*