by Hogan Paschal 1

With increas­ing fre­quen­cy, gov­ern­ment enti­ties through­out the Unit­ed States are har­ness­ing the inves­tiga­tive pow­er of loca­tion track­ing, includ­ing scan­ning license plates, col­lect­ing cell tow­er data, and using GPS tech­nol­o­gy. 2 Fre­quent­ly, the gov­ern­ment con­ducts this sur­veil­lance for pro­longed peri­ods of time, con­tin­u­ous­ly, and with­out a war­rant. Courts are grap­pling with the con­sti­tu­tion­al­i­ty of pro­longed, sur­rep­ti­tious loca­tion track­ing. Most recent­ly, the Supreme Court dealt with the issue in Unit­ed States v. Jones, a case in which the gov­ern­ment attached a GPS track­ing device to a person’s car for twen­ty-eight days. 3 In order to check against the increased poten­tial for gov­ern­ment abuse of this search pow­er, courts must devel­op and apply Fourth Amend­ment pro­tec­tions appro­pri­ate for a new tech­no­log­i­cal age.

Advo­cates of war­rant­less loca­tion track­ing argue that, because GPS cap­tures only a person’s move­ments in pub­lic, the prac­tice is con­sti­tu­tion­al, as the Fourth Amend­ment does not pro­tect that which a per­son know­ing­ly dis­clos­es to the pub­lic. Rather, they would con­tend that the Fourth Amend­ment pro­tects only that which a per­son can attribute a rea­son­able expec­ta­tion of privacy.

How­ev­er, this argu­ment pre­sumes that the Fourth Amend­ment is exclu­sive­ly and entire­ly aimed at pro­tect­ing pri­va­cy. It is not. The Fourth Amend­ment was designed to check gov­ern­ment pow­er. The Framers draft­ed the Amend­ment in response to the whol­ly unbound­ed search pow­er of the British gov­ern­ment. Chief Jus­tice Roberts recent­ly observed:

Our cas­es have rec­og­nized that the Fourth Amend­ment was the found­ing generation’s response to the reviled “gen­er­al war­rants” and “writs of assis­tance” of the colo­nial era, which allowed British offi­cers to rum­mage through homes in an unre­strained search for evi­dence of crim­i­nal activ­i­ty. Oppo­si­tion to such search­es was in fact one of the dri­ving forces behind the Rev­o­lu­tion itself. 4

In prac­tice, the Fourth Amend­ment restrains gov­ern­ment search pow­er through its war­rant require­ment, which impos­es a judi­cial check on the exec­u­tive branch’s pow­er to search. 5

Pro­tec­tion from unlim­it­ed gov­ern­ment search pow­er does not end with the Fourth Amend­ment. For most of our his­to­ry, prac­ti­cal lim­its com­ple­ment­ed the con­sti­tu­tion­al pro­tec­tions of the war­rant require­ment. 6For exam­ple, before the advent of smart phones, a police officer’s search of a per­son was prac­ti­cal­ly lim­it­ed to that which would fit in a person’s pock­ets, thus con­strain­ing an officer’s search dis­cre­tion. The stor­age capac­i­ty of a person’s pock­ets is incred­i­bly more lim­it­ed than that of a cloud-con­nect­ed smart­phone with­in that pock­et. 7In this way, con­sti­tu­tion­al and prac­ti­cal pro­tec­tions worked in tan­dem to cur­tail gov­ern­ment search pow­er. 8 Tech­no­log­i­cal devel­op­ments have dis­solved these prac­ti­cal con­straints and “erode[d] the pri­va­cy guar­an­teed by the Fourth Amend­ment.” 9 When such ero­sion occurs, the Court gen­er­al­ly restores the pro­tec­tion pre­vi­ous­ly pro­vid­ed by prac­ti­cal con­straints by requir­ing a war­rant, as it did with smart­phones in Riley v. Cal­i­for­nia.


By pro­vid­ing the gov­ern­ment with extrasen­so­ry abil­i­ties, pro­longed loca­tion track­ing sim­i­lar­ly elim­i­nates prac­ti­cal checks on gov­ern­ment pow­er in two ways. First, extrasen­so­ry tech­nol­o­gy does not mere­ly enhance nor­mal human per­cep­tion; it also over­comes lim­i­ta­tions imposed by the five sens­es. 10 For exam­ple, in Unit­ed States v. Kyl­lo, war­rant­less police use of infrared imag­ing tech­nol­o­gy allowed police to per­ceive heat being giv­en off by the home. 11 With­out the tech­nol­o­gy, the police would have been unable to per­ceive the excess heat being giv­en off by the defendant’s mar­i­jua­na-grow­ing oper­a­tion. Because the tech­nol­o­gy pro­vid­ed such extrasen­so­ry infor­ma­tion, the Court held that the war­rant­less use of the tech­nol­o­gy in the con­text of the home vio­lat­ed the Fourth Amend­ment; the Court there­by restored the check pre­vi­ous­ly pro­vid­ed by the lim­i­ta­tions of human eyesight.

Addi­tion­al­ly, by aggre­gat­ing a person’s GPS loca­tion data, the gov­ern­ment can har­vest high­ly inti­mate per­son­al details that any dis­crete data point would not oth­er­wise reveal. 12 For exam­ple, com­put­er sci­en­tists can uti­lize algo­rithms and sta­tis­ti­cal analy­ses to pre­dict a person’s gen­der, mar­i­tal sta­tus, occu­pa­tion, and age based on as lit­tle as one week’s worth of GPS loca­tion his­to­ry. 13 Just as the ther­mal imagery tech­nol­o­gy at issue in Kyl­lo allowed an observ­er to gath­er infor­ma­tion about a home that would not oth­er­wise be avail­able, so can aggre­gat­ed loca­tion sur­veil­lance trans­late a person’s week­ly trav­els into sen­si­tive per­son­al data. In these ways, extrasen­so­ry tech­nol­o­gy expands the scope of the government’s pow­er to search.

Sec­ond, pro­longed loca­tion data erodes the prac­ti­cal con­straint that gov­ern­ment resources pre­vi­ous­ly imposed on search pow­er. Loca­tion track­ing can pro­duce an aston­ish­ing vol­ume of infor­ma­tion at very lit­tle cost to the gov­ern­ment. Before loca­tion-track­ing tech­nol­o­gy was avail­able, law enforce­ment would have had to use human sur­veil­lance to con­tin­u­ous­ly track a person’s loca­tion. Such sur­veil­lance would have required an enor­mous amount of resources, and would like­ly only occur if the inves­ti­ga­tion was of unusu­al impor­tance. 14 In oth­er words, the expense of pro­longed loca­tion sur­veil­lance lim­it­ed the fre­quen­cy and length of the government’s search pow­er. How­ev­er, when tech­nol­o­gy elim­i­nates the costs of sur­veil­lance, the government’s pow­er to search becomes more exten­sive. The ero­sion of this prac­ti­cal con­straint presents huge poten­tial for abuse, as Jus­tice Sotomay­or rec­og­nized in her own Jones con­cur­rence: “[T]he Government’s unre­strained pow­er to assem­ble data that reveal pri­vate aspects of iden­ti­ty is sus­cep­ti­ble to abuse. The net result is that GPS monitoring—by mak­ing avail­able at a rel­a­tive­ly low cost such a sub­stan­tial quan­tum of inti­mate infor­ma­tion about any per­son whom the Gov­ern­ment, in its unfet­tered dis­cre­tion, choos­es to trace—may alter the rela­tion­ship between cit­i­zens and gov­ern­ment in a way that is inim­i­cal to demo­c­ra­t­ic soci­ety.” 15


Because pro­longed GPS track­ing erodes the afore­men­tioned prac­ti­cal con­straints, the gov­ern­men­t’s use of such tech­nol­o­gy facil­i­tates whol­ly unchecked search pow­er, which the Fourth Amend­ment should pre­clude. This is true even under the Court’s cur­rent test of “rea­son­able expec­ta­tions of pri­va­cy” estab­lished in Katz v. Unit­ed States: a per­son may rea­son­ably expect that loca­tion track­ing might reveal where that per­son has trav­eled in pub­lic, but a per­son cer­tain­ly does not rea­son­ably expect that this loca­tion data, in the aggre­gate, will reveal per­son­al details such as sex­u­al ori­en­ta­tion or med­ical ail­ments. 16

Courts must restore these safe­guards by requir­ing a warrant—and the judi­cial over­sight accom­pa­ny­ing it—for the government’s use of pro­longed loca­tion track­ing. Oth­er­wise, the courts invite the devel­op­ment of a sur­veil­lance state in which law enforce­ment makes end runs around the Fourth Amend­ment by assem­bling pub­lic infor­ma­tion to dis­cov­er high­ly sen­si­tive pri­vate infor­ma­tion. The Con­sti­tu­tion sim­ply can­not stand for such an Orwellian alternative.



  1. This piece is the author’s com­men­tary on one of the ques­tions pre­sent­ed at the 2016 Spong Con­sti­tu­tion­al Law Moot Court Tour­na­ment held at the William & Mary School of Law in Williams­burg, Vir­ginia. The issue at heart of the prob­lem was whether war­rant­less, pro­longed loca­tion track­ing vio­lat­ed the Fourth Amend­ment. The views expressed in this arti­cle do not nec­es­sar­i­ly rep­re­sent the views of the author on this point of law. Rather, this arti­cle is a dis­til­la­tion of one side of an argu­ment, which the author rep­re­sent­ed.
  2. See You Are Being Tracked, Amer­i­can Civ­il Lib­er­ties Union, (last vis­it­ed Apr. 24, 2016) (license plate scan­ners); Unit­ed States v. Jones, 132 S. Ct. 945 (2012) (GPS track­ing); Unit­ed States v. Davis, 785 F.3d 498, 519 (11th Cir.), cert. denied, (2015) (cell tow­er data).
  3. In 2011, the Supreme Court con­sid­ered whether GPS track­ing con­sti­tut­ed a Fourth Amend­ment search. Jones, 132 S. Ct. at 947. In that case, the gov­ern­ment attached a GPS track­ing device to the under­side of a suspect’s car and tracked the suspect’s loca­tion for 28 days with­out pause. Id. The Court held that the government’s sur­veil­lance vio­lat­ed the Fourth Amend­ment, because attach­ing the track­ing device was a phys­i­cal tres­pass. Id. at 954. The Court left open the ques­tion of whether pro­longed GPS track­ing, absent a phys­i­cal tres­pass, is a Fourth Amend­ment search. Id. at 964 (Ali­to, J., con­cur­ring).
  4. Riley v. Cal­i­for­nia, 134 S. Ct. 2473, 2494 (2014). See also Fabio Arcila, Jr., Death of Sus­pi­cion, 51 Wm. & Mary L. Rev. 1275, 1284 (2010) (“The Framers’ key con­cern behind their desire to ban gen­er­al war­rants and writs of assis­tance was to lim­it search dis­cre­tion.”) (inter­nal cita­tions omit­ted); Renée McDon­ald Hutchins, Tied Up in Knotts? GPS Tech­nol­o­gy and the Fourth Amend­ment, 55 UCLA L. Rev. 409, 444 (2007) (“The Fourth Amend­ment, at its core, reg­u­lates police con­duct.”).
  5. Riley, 134 S. Ct. at 2482 (inter­nal cita­tions omit­ted). See also Unit­ed States v. Karo, 468 U.S. 716, 717 (1984) (“Requir­ing a war­rant will have the salu­tary effect of ensur­ing that use of [sur­veil­lance tech­nol­o­gy] is not abused, by impos­ing upon agents the require­ment that they demon­strate in advance their jus­ti­fi­ca­tion for the desired search.”); Katz v. Unit­ed States, 389 U.S. 347, 357 (1967) (“[T]he Con­sti­tu­tion requires that the delib­er­ate, impar­tial judg­ment of a judi­cial offi­cer [in issu­ing a war­rant] . . . be inter­posed between the cit­i­zen and the police.”) (inter­nal cita­tions omit­ted).
  6. See, e.g., Jones, 132 S. Ct. at 963 (Ali­to, J., con­cur­ring) (“In the pre-com­put­er age, the great­est pro­tec­tions of pri­va­cy were nei­ther con­sti­tu­tion­al nor statu­to­ry but prac­ti­cal.”).
  7. See Riley, 134 S. Ct. at 2478 (“Before cell phones, a search of a per­son was lim­it­ed by phys­i­cal real­i­ties and tend­ed as a gen­er­al mat­ter to con­sti­tute only a nar­row intru­sion on pri­va­cy.”).
  8. See, e.g., Jones, 132 S. Ct. at 963 (Ali­to, con­cur­ring).
  9. Kyl­lo v. Unit­ed States, 533 U.S. 27, 35 (2001).
  10. See gen­er­al­ly Hutchins, supra note 4, at §II(C). For exam­ple, com­pare binoc­u­lars with infrared imag­ing tech­nol­o­gy. Binoc­u­lars mag­ni­fy human sight, but do not reveal any­thing oth­er­wise imper­cep­ti­ble to nor­mal vision. On the oth­er hand, infrared imag­ing tech­nol­o­gy allows a per­son to effec­tive­ly see through walls. See Kyl­lo, at 29–30. Binoc­u­lars are sense-enhanc­ing, where­as infrared imag­ing is extra-sen­so­ry.
  11. 533 U.S. at 40.
  12. See, e.g., Unit­ed States v. May­nard, 615 F.3d 544, 562 (D.C. Cir. 2010) (“Pro­longed sur­veil­lance reveals types of infor­ma­tion not revealed by short-term sur­veil­lance, such as what a per­son does repeat­ed­ly, what he does not do, and what he does ensem­ble. These types of infor­ma­tion can each reveal more about a per­son than does any indi­vid­ual trip in iso­la­tion.”), aff’d in part sub nom. Unit­ed States v. Jones, 132 S. Ct. 945 (2012); Peo­ple v. Weaver, 12 N.Y.3d 433, 442 (N.Y. 2009) (not­ing pro­longed loca­tion mon­i­tor­ing “yields . . . a high­ly detailed pro­file, not sim­ply of where we go, but by easy infer­ence, of our associations—political, reli­gious, ami­ca­ble and amorous, to name only a few—and of the pat­tern of our pro­fes­sion­al and avo­ca­tion­al pur­suits.”)
  13. See, e.g., San­ja Brdar, Dubravko Culi­brk & Vladimir Crno­je­vic, Demo­graph­ic Attrib­ut­es Pre­dic­tion on the Real-World Mobile Data, Mobile Data Chal­lenge 2012 (by Nokia) Work­shop, (last vis­it­ed Apr. 24, 2016); Steven M. Bellovin, et al., When Enough is Enough: Loca­tion Track­ing, Mosa­ic The­o­ry, and Machine Learn­ing, 8 N.Y.U. J.L. & Lib­er­ty 555, 557–558 (2014).
  14. 132 S. Ct. at 963–64 (Ali­to, J., con­cur­ring) (“Tra­di­tion­al sur­veil­lance for any extend­ed peri­od of time was dif­fi­cult and cost­ly and there­fore rarely under­tak­en . . . Only an inves­ti­ga­tion of unusu­al impor­tance could have jus­ti­fied such an expen­di­ture of law enforce­ment resources.”) (inter­nal cita­tions omit­ted).
  15. Id. at 956 (Sotomay­or, J., con­cur­ring) (inter­nal cita­tions omit­ted).
  16. See Katz, 389 U.S. at 361 (Har­lan, con­cur­ring); May­nard, 615 F.3d at 562.