Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-402_h315.pdf
Page Number: 5

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

1 

Opinion of the Court 

NOTICE:  This opinion is subject to formal revision before publication in the
preliminary  print  of  the  United  States  Reports.  Readers  are  requested  to
notify the Reporter of Decisions, Supreme Court of the United States, Wash-
ington,  D. C.  20543,  of  any  typographical  or  other  formal  errors,  in  order
that corrections may be made before the preliminary print goes to press. 

SUPREME COURT OF THE UNITED STATES 

_________________ 

No. 16–402 
_________________ 

TIMOTHY IVORY CARPENTER, PETITIONER v.
 
UNITED STATES
 

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

APPEALS FOR THE SIXTH CIRCUIT
 

[June 22, 2018] 

CHIEF  JUSTICE  ROBERTS  delivered  the  opinion  of  the

Court. 

This  case  presents  the  question  whether  the  Govern-
ment  conducts  a  search  under  the  Fourth  Amendment 
when it accesses historical cell phone records that provide
a comprehensive chronicle of the user’s past movements. 

I 

A 

There are 396 million cell phone service accounts in the
United  States—for  a  Nation  of  326  million  people.    Cell 
phones  perform  their  wide  and  growing  variety  of  func-
tions  by  connecting  to  a  set  of  radio  antennas  called  “cell
sites.”  Although cell sites are usually mounted on a tower,
they  can  also  be  found  on  light  posts,  flagpoles,  church
steeples, or the sides of buildings.  Cell sites typically have
several  directional  antennas  that  divide  the  covered  area 
into sectors. 

Cell  phones  continuously  scan  their  environment  look-
ing  for  the  best  signal,  which  generally  comes  from  the 
closest  cell  site.  Most  modern  devices,  such  as 
smartphones, tap into  the wireless network several times