Document ID: ./input/supremecourt_opinions/opinions/17pdf/16-402_h315.pdf
Page Number: 12

8 

CARPENTER v. UNITED STATES 

Opinion of the Court 

privacy in his movements from one place to another.”  Id., 
at  281,  282.    Since  the  movements  of  the  vehicle  and  its 
final destination had been “voluntarily conveyed to anyone 
who  wanted  to  look,”  Knotts  could  not  assert  a  privacy
interest in the information obtained.  Id., at 281. 

This  Court  in  Knotts,  however,  was  careful  to  distin-
guish between the rudimentary tracking facilitated by the
beeper  and  more  sweeping  modes  of  surveillance.  The 
Court emphasized the “limited use which the government
made  of  the  signals from this particular beeper” during a 
discrete  “automotive  journey.”  Id.,  at  284,  285.    Signifi-
cantly, the Court reserved the question whether “different
constitutional principles may be applicable” if “twenty-four
hour  surveillance  of  any  citizen  of  this  country  [were] 
possible.”  Id., at 283–284. 

Three  decades  later,  the  Court  considered  more  sophis-
ticated  surveillance  of  the  sort  envisioned  in  Knotts  and 
found that different principles did indeed apply.  In United 
States  v.  Jones,  FBI  agents  installed  a  GPS  tracking  de-
vice  on  Jones’s  vehicle  and  remotely  monitored  the  vehi-
cle’s  movements  for  28  days.    The  Court  decided  the  case 
based  on  the  Government’s  physical  trespass  of  the  vehi-
cle.  565 U. S., at 404–405.  At the same time, five Justices 
agreed  that  related  privacy  concerns  would  be  raised  by,
for  example,  “surreptitiously  activating  a  stolen  vehicle
detection system” in Jones’s car to track Jones himself, or
conducting GPS tracking of his cell phone.  Id., at 426, 428 
(ALITO,  J.,  concurring 
id.,  at  415 
in 
(SOTOMAYOR,  J.,  concurring).    Since  GPS  monitoring  of  a 
vehicle  tracks  “every  movement”  a  person  makes  in  that
vehicle,  the  concurring  Justices  concluded  that  “longer
term  GPS  monitoring  in  investigations  of  most  offenses 
impinges on expectations of privacy”—regardless whether 
those  movements  were  disclosed  to  the  public  at  large. 
Id.,  at  430  (opinion  of  ALITO,  J.);  id.,  at  415  (opinion  of 

judgment);