Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-402_h315.pdf
Page Number: 15.0

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

11 

Opinion of the Court 

At  the  same  time,  the  fact  that  the  individual  continu-
ously reveals his location to his wireless carrier implicates
the  third-party  principle  of  Smith  and  Miller.  But  while 
the third-party doctrine applies to telephone numbers and 
bank  records,  it  is  not  clear  whether  its  logic  extends  to 
the  qualitatively  different  category  of  cell-site  records.
After all, when Smith was decided in 1979, few could have 
imagined  a  society  in  which  a  phone  goes  wherever  its
owner  goes,  conveying  to  the  wireless  carrier  not  just
dialed  digits,  but  a  detailed  and  comprehensive  record  of
the person’s movements.

We  decline  to  extend  Smith  and  Miller  to  cover  these 
novel  circumstances.    Given  the  unique  nature  of  cell
phone  location  records,  the  fact  that  the  information  is 
held by a third party does not by itself overcome the user’s 
claim  to  Fourth  Amendment  protection.    Whether  the 
Government employs its own surveillance technology as in 
Jones or leverages the technology of a wireless carrier, we
hold that an individual maintains a legitimate expectation
of  privacy  in  the  record  of  his  physical  movements  as 
captured  through  CSLI.    The  location  information  ob-
tained from Carpenter’s wireless carriers was the product 
of a search.3 

—————— 

3 The  parties  suggest  as  an  alternative  to  their  primary  submissions
that the acquisition of CSLI becomes a search only if it extends beyond
a limited period.  See Reply Brief 12 (proposing a 24-hour cutoff); Brief
for United States 55–56 (suggesting a seven-day cutoff).  As part of its 
argument,  the  Government  treats  the  seven  days  of  CSLI  requested
from Sprint as the pertinent period, even though Sprint produced only 
two  days  of  records.   Brief  for  United  States  56.    Contrary  to  JUSTICE 
KENNEDY’s assertion, post, at 19, we need not decide whether there is a 
limited  period  for  which  the  Government  may  obtain  an  individual’s
historical  CSLI  free  from  Fourth  Amendment  scrutiny,  and  if  so,  how 
long that period might be.  It is sufficient for our purposes today to hold
that  accessing  seven  days  of  CSLI  constitutes  a  Fourth  Amendment
search.