Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-402_h315.pdf
Page Number: 18

14 

CARPENTER v. UNITED STATES 

Opinion of the Court 

Unlike with the GPS device in Jones, police need not even 
know in advance whether they want to follow a particular 
individual, or when. 

Whoever  the  suspect  turns  out  to  be,  he  has  effectively
been tailed every moment of every day for five years, and
the  police  may—in  the  Government’s  view—call  upon  the
results  of  that  surveillance  without  regard  to  the  con-
straints  of  the  Fourth  Amendment.    Only  the  few  with-
out  cell  phones  could  escape  this  tireless  and  absolute 
surveillance. 

The  Government  and  JUSTICE  KENNEDY  contend,  how-
ever,  that  the  collection  of  CSLI  should  be  permitted
because  the  data  is  less  precise  than  GPS  information.
Not to worry, they maintain, because the location records
did  “not  on  their  own  suffice  to  place  [Carpenter]  at  the 
crime  scene”;  they  placed  him  within  a  wedge-shaped 
sector ranging from one-eighth to four square miles.  Brief 
for United States 24; see post, at 18–19.  Yet the Court has 
already rejected the proposition that “inference insulates a 
search.”  Kyllo,  533  U. S.,  at  36.    From  the  127  days  of 
location data it received, the Government could, in combi-
nation  with  other  information,  deduce  a  detailed  log  of 
Carpenter’s movements, including when he was at the site
of  the  robberies.  And  the  Government  thought  the  CSLI
accurate  enough  to  highlight  it  during  the  closing  argu-
ment of his trial.  App. 131. 

At  any  rate,  the  rule  the  Court  adopts  “must  take  ac-
count  of  more  sophisticated  systems  that  are  already  in
use or in development.”  Kyllo, 533 U. S., at 36.  While the 
records  in  this  case  reflect  the  state  of  technology  at  the
start  of  the  decade,  the  accuracy  of  CSLI  is  rapidly  ap-
proaching GPS-level precision.  As the number of cell sites 
has proliferated, the geographic area covered by each  cell 
sector  has  shrunk,  particularly  in  urban  areas.    In  addi-
tion, with new technology measuring the time and angle of
signals hitting their towers, wireless carriers already have