Document ID: ./input/supremecourt_opinions/opinions/19pdf/18-556_e1pf.pdf
Page Number: 16.0

4 

KANSAS v. GLOVER 

KAGAN, J., concurring 

and-dry), when the officer learns a car has two or more reg-
istered owners, the balance of circumstances may tip away
from reasonable suspicion that the one with the revoked li-
cense is driving.  And so too, the attributes of the car may 
be relevant.  Consider if a car bears the markings of a peer-
to-peer carsharing service; or compare the likelihoods that 
someone  other  than  the  registered  owner  is  driving  (1)  a 
family minivan and (2) a Ferrari.  The officer himself may
have a wealth of accumulated information about such mat-
ters,  and  the  defendant  may  probe  what  that  knowledge
suggests about the stop at issue.

Such a challenge may also use statistical evidence, which
is  almost  daily  expanding  in  sophistication  and  scope.
States or municipalities often keep information about “hit 
rates” in stops like this one—in other words, the frequency 
with which those stops discover unlicensed drivers behind 
the wheel.  See generally Brief for Andrew Manuel Crespo 
as  Amicus  Curiae  23–27.    Somewhat  less  direct  but  also 
useful are state and local data (collected by governments, 
insurance companies, and academics alike) about the aver-
age number of drivers for each registered automobile and 
the  extent  to  which  unlicensed  persons  continue  to  drive.
See id., at 13–18.  (If, to use an extreme example, every car 
had 10 associated drivers, and losing a license reduced driv-
ing time by 90%, an officer would not have reasonable sus-
picion for a stop.)  Here too, defendants may question testi-
fying  officers  about  such  information.  Indeed,  an  officer 
may have his own hit rate, which if low enough could itself 
negate  reasonable  suspicion.    See,  e.g.,  United  States  v. 
Cortez-Galaviz,  495  F. 3d  1203,  1208–1209  (CA10  2007) 
(Gorsuch, J.) (considering, as part of the reasonable suspicion
inquiry, the frequency of an officer’s misses and the accu-
racy of the database on which he relied).* 

—————— 

* Of course, aggregate statistics of this kind cannot substitute for the 
individualized suspicion that the Fourth Amendment requires.  See, e.g.,