Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-402_h315.pdf
Page Number: 16.0

12 

CARPENTER v. UNITED STATES 

Opinion of the Court 

A 

A  person  does  not  surrender  all  Fourth  Amendment 
protection  by  venturing  into  the  public  sphere.    To  the 
contrary, “what [one] seeks to preserve as private, even in 
an  area  accessible  to  the  public,  may  be  constitutionally 
protected.”  Katz, 389 U. S., at 351–352.  A majority of this
Court  has  already  recognized  that  individuals  have  a
reasonable  expectation  of  privacy  in  the  whole  of  their 
physical  movements.  Jones,  565  U. S.,  at  430  (ALITO,  J., 
concurring  in  judgment);  id.,  at  415  (SOTOMAYOR,  J., 
concurring).    Prior  to  the  digital  age,  law  enforcement
might have pursued a suspect for a brief stretch, but doing
so “for any extended period of time was difficult and costly
and  therefore  rarely  undertaken.”  Id.,  at  429  (opinion  of 
ALITO,  J.).  For  that  reason,  “society’s  expectation  has 
been that law enforcement agents and others would not—
and indeed, in the main, simply could not—secretly moni-
tor and catalogue every single movement of an individual’s
car for a very long period.”  Id., at 430. 

Allowing  government  access  to  cell-site  records  contra-
venes that expectation.  Although such records are gener-
ated  for  commercial  purposes,  that  distinction  does  not
negate  Carpenter’s  anticipation  of  privacy  in  his  physical
location.  Mapping  a  cell  phone’s  location  over  the  course
of  127  days  provides  an  all-encompassing  record  of  the
holder’s whereabouts.  As with GPS information, the time-
stamped data provides an intimate window into a person’s
life,  revealing  not  only  his  particular  movements,  but 
through  them  his  “familial,  political,  professional,  reli-
gious,  and  sexual  associations.”    Id.,  at  415  (opinion  of
SOTOMAYOR,  J.).  These  location  records  “hold  for  many
Americans  the  ‘privacies  of  life.’ ”    Riley,  573  U. S.,  at  ___ 
(slip op., at 28) (quoting Boyd, 116 U. S., at 630).  And like 
GPS  monitoring,  cell  phone  tracking  is  remarkably  easy,
cheap,  and  efficient  compared  to  traditional  investigative 
tools.  With just the click of a button, the Government can