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Page Number: 10.0

6 

CARPENTER v. UNITED STATES 

Opinion of the Court 

analysis is informed by historical understandings “of what
was  deemed  an  unreasonable  search  and  seizure  when 
[the Fourth Amendment] was adopted.”  Carroll v. United 
States, 267 U. S. 132, 149 (1925).  On this score, our cases 
have  recognized  some  basic  guideposts.  First,  that  the 
Amendment seeks to secure “the  privacies of life” against 
“arbitrary  power.”  Boyd  v.  United  States,  116  U. S.  616, 
630  (1886).   Second,  and  relatedly,  that  a  central  aim  of
the  Framers  was  “to  place  obstacles  in  the  way  of  a  too
permeating  police  surveillance.”    United  States  v.  Di  Re, 
332 U. S. 581, 595 (1948).

We  have  kept  this  attention  to  Founding-era  under-
standings in mind when applying the Fourth Amendment
to  innovations  in  surveillance  tools.  As  technology  has
enhanced  the  Government’s  capacity  to  encroach  upon
areas  normally  guarded  from  inquisitive  eyes,  this  Court 
has  sought  to  “assure[  ]  preservation  of  that  degree  of 
privacy against government that existed when the Fourth 
Amendment  was  adopted.”  Kyllo  v.  United  States,  533 
U. S. 27, 34 (2001).  For that reason, we rejected in Kyllo a 
“mechanical interpretation” of the Fourth Amendment and 
held that use of a thermal imager to detect heat radiating 
from the side of the defendant’s home was a search.  Id., at 
35.  Because  any  other  conclusion  would  leave  homeown-
ers “at the mercy of advancing technology,” we determined
that  the  Government—absent  a  warrant—could  not  capi-
talize  on  such  new  sense-enhancing  technology  to  explore 
—————— 

exclusively  property-based  approach.  Post,  at  1–2,  17–21  (THOMAS  J., 
dissenting);  post,  at  6–9  (GORSUCH,  J.,  dissenting).    Katz  of  course 
“discredited” the “premise that property interests control,” 389 U. S., at
353,  and we have repeatedly emphasized  that privacy interests do not
rise  or  fall  with  property  rights,  see,  e.g.,  United  States  v.  Jones,  565 
U. S.  400,  411  (2012)  (refusing  to  “make  trespass  the  exclusive  test”); 
Kyllo  v.  United  States,  533  U. S.  27,  32  (2001)  (“We  have  since  decou-
pled violation of a person’s Fourth Amendment rights from trespassory
violation  of  his  property.”).    Neither  party  has  asked  the  Court  to 
reconsider Katz in this case.