Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-402_h315.pdf
Page Number: 1.0

(Slip Opinion) 

OCTOBER  TERM,  2017 

1 

Syllabus 

NOTE:  Where  it  is  feasible,  a  syllabus  (headnote)  will  be  released,  as  is
being  done  in  connection  with  this  case,  at  the  time  the  opinion  is  issued.
The  syllabus  constitutes  no  part  of  the  opinion  of  the  Court  but  has  been
prepared  by  the  Reporter  of  Decisions  for  the  convenience  of  the  reader. 
See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337. 

SUPREME COURT OF THE UNITED STATES 

Syllabus 

CARPENTER v. UNITED STATES 

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR 
THE SIXTH CIRCUIT 

No. 16–402.  Argued November 29, 2017—Decided June 22, 2018 

Cell phones perform their wide and growing variety of functions by con-
tinuously  connecting  to  a  set  of  radio  antennas  called  “cell  sites.”
Each time a phone connects to a cell site, it generates a time-stamped
record known as cell-site location information (CSLI).  Wireless carri-
ers collect and store this information for their own business purposes.
Here, after the FBI identified the cell phone numbers of several rob-
bery  suspects,  prosecutors  were  granted  court  orders  to  obtain  the
suspects’  cell  phone  records  under  the  Stored  Communications  Act.
Wireless  carriers  produced  CSLI  for  petitioner  Timothy  Carpenter’s 
phone, and the Government was able to obtain 12,898 location points
cataloging Carpenter’s movements over 127 days—an average of 101 
data points per day.  Carpenter moved to suppress the data, arguing
that  the  Government’s  seizure  of  the  records  without  obtaining  a
warrant  supported  by  probable  cause  violated  the  Fourth  Amend-
ment.  The  District  Court  denied  the  motion,  and  prosecutors  used
the records at trial to show that Carpenter’s phone was near four of
the robbery locations at the time those robberies occurred.   Carpen-
ter was convicted.  The Sixth Circuit affirmed, holding that Carpen-
ter  lacked  a  reasonable  expectation  of  privacy  in  the  location  infor-
mation collected by the FBI because he had shared that information
with his wireless carriers. 

Held: 

1. The  Government’s  acquisition  of  Carpenter’s  cell-site  records 

was a Fourth Amendment search.  Pp. 4–18.

(a) The  Fourth  Amendment  protects  not  only  property  interests
but certain expectations of privacy as well.  Katz v. United States, 389 
U. S.  347,  351.    Thus,  when  an  individual  “seeks  to  preserve  some-
thing as private,” and his expectation of privacy is “one that society is