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

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

13 

Opinion of the Court 

access  each  carrier’s  deep  repository  of  historical  location
information at practically no expense.

In  fact,  historical  cell-site  records  present  even  greater
privacy concerns than the GPS monitoring of a vehicle we
considered  in  Jones.  Unlike  the  bugged  container  in 
Knotts or the car in Jones, a cell phone—almost a “feature
of  human  anatomy,”  Riley,  573  U. S.,  at  ___  (slip  op.,  at 
9)—tracks  nearly  exactly  the  movements  of  its  owner.
While  individuals  regularly  leave  their  vehicles,  they
compulsively carry cell phones with them all the time.  A 
cell phone faithfully follows its owner beyond public thor-
oughfares  and  into  private  residences,  doctor’s  offices,
political  headquarters,  and  other  potentially  revealing 
locales.  See id., at ___ (slip op., at 19) (noting that “nearly 
three-quarters  of  smart  phone  users  report  being  within 
five feet of their phones most of the time, with 12% admit-
ting  that  they  even  use  their  phones  in  the  shower”); 
contrast  Cardwell  v.  Lewis,  417  U. S.  583,  590  (1974) 
(plurality  opinion)  (“A  car  has  little  capacity  for  escaping
public  scrutiny.”).  Accordingly,  when  the  Government
tracks the location of a cell phone it achieves near perfect 
surveillance, as if it had attached an ankle monitor to the 
phone’s user. 

Moreover,  the  retrospective  quality  of  the  data  here
gives  police  access  to  a  category  of  information  otherwise 
unknowable.    In  the  past,  attempts  to  reconstruct  a  per-
son’s  movements  were  limited  by  a  dearth  of  records  and 
the  frailties  of  recollection.  With  access  to  CSLI,  the 
Government  can  now  travel  back  in  time  to  retrace  a 
person’s whereabouts, subject only to the retention polices 
of the wireless carriers, which currently maintain records
for  up  to  five  years.    Critically,  because  location  infor-
mation  is  continually  logged  for  all  of  the  400  million 
devices  in  the  United  States—not  just  those  belonging  to 
persons who might happen to come under investigation—
this  newfound  tracking  capacity  runs  against  everyone.