resented a decreasing reliance on human skill in favor of automation. As
the Supreme Court itself observed, no
one in Carpenter’s position—anyone
with a cellphone—could escape the “
inescapable and automatic nature of its
collection.”i This represents a change
in the scale and scope of policing tasks
that augment, not just supplement,
what the police do.
The government’s case against Carpenter involved plotting points on a literal map for a jury, but the reasoning of
the Court’s opinion points to concerns
that could easily be applied to the police
use of artificial intelligence. The Court
was concerned about tools that had extended beyond “augmenting the sensory faculties bestowed upon [the police]
at birth.”j Tools that are “remarkably
easy, cheap, and efficient compared
to traditional investigative methods”k
merited new ways of applying the
Fourth Amendment’s protections.
To be clear: Carpenter is not a case
explicitly about artificial intelligence.
And the Supreme Court was adamant
about trying to limit its decision to the
collection of cell site location information. But that self-conscious restraint
is not likely to last. In describing those
changes in policing that called for a
new Fourth Amendment approach,
the Court happened to describe some
of the key features of artificial intelligence tools being adopted by police
departments: they are cheap, powerful, ubiquitous, automated, and invasive of privacy in ways that are novel
and alarming. Whether the courts will
embrace this potential approach to artificial intelligence tools in policing remains to be seen.
i 138 S. Ct. at 2223 (emphasis added).
UnitedStatesv.Knotts, 103 S. Ct. 1081, 1086 (1983).
k 138 S. Ct. at 2219.
1. Gorner, J. Chicago police use ‘heat list’ as a strategy to
prevent violence. Chicago Tribune (Aug. 21, 2013).
2. Joh, E.J. Automated policing. Ohio St. J. Crim. L. 15 ,
3. Joh, E.J. The new surveillance discretion: Automated
suspicion, big data, and policing. Harv. L. & Pol’y Rev.
10, 15 (2016).
4. Jouvenal, J. The new way police are surveilling you:
Calculating your threat ‘score.’ Washington Post (Jan.
Elizabeth E. Joh ( email@example.com) is a Professor
of Law at the University of California, Davis School
of Law, USA.
Copyright held by author.
The Supreme Court has long recognized that you lose Fourth Amendment protection in information you
provide to third parties, such as banks
and phone companies. In a 1979 decision, the Court held that the Fourth
Amendment did not apply when the
government intercepted the numbers
dialed out by a suspect by installing a
pen register at the phone company.
Once handed over to a third party, that
information lost the protection that
would normally have required the police to a obtain a warrant beforehand.
The phone numbers dialed out by
landlines in the 1970s are a far cry,
though, from our relationship to data
today. It is impossible to live a normal
life now without providing all kinds of
information to third parties. Indeed,
both our heavy reliance on the Internet
and the Internet of Things means we
are constantly streaming information to
Despite the dramatic changes in the
technologies used by everyone, including the police, these legal concepts
about knowing exposure and third
parties remain robust parts of Fourth
Amendment law. What then, can we expect from the courts as the police rely
even more on artificial intelligence?
It turns out the U.S. Supreme Court
has already hinted at how it might
one day approach the question. These
hints come from an unlikely source:
the Court’s 2018 decision in Carpenter
v. United States.b Carpenter is not a case
about artificial intelligence. It involves
the investigation of a string of cellphone store robberies in the Midwest.
Looking for evidence connecting Timothy Carpenter to the crimes, FBI agents
asked his wireless services providers for
his phone’s cell-site location information during the times of the robberies.
The FBI eventually received more than
12,000 location points that showed Carpenter’s phone—and by implication
Carpenter himself—near the robberies
during the times they occurred.
The Supreme Court ultimately decided in Carpenter’s favor and ruled
the collection of this location information amounted to a “search” under the
Fourth Amendment. That conclusion
meant the government should have obtained a warrant before collecting the
b 138 S. Ct. 2206 (2018).
data. What was remarkable about the
decision was the Court’s expansion of
Fourth Amendment protection to information that was held by Carpenter’s
wireless carrier, not Carpenter himself.
Instead, the Court focuses in Carpenter
on the nature of information sought:
“the qualitatively different category of
This much has been commented
upon widely. But the Court also said
more in Carpenter that has implica-
tions for artificial intelligence: it also
focused on three distinctive character-
istics of the policing involved.d First,
what concerned the Carpenter major-
ity was a policing technology that was
both superhuman and cheap. Unlike
the “nosy neighbor who keeps an eye
on comings and goings,” the technol-
ogy used by the police was “ever alert,
and [its] memory is nearly infallible.”e
Few practical limitations exist when
police can rely on “tireless and absolute
Second, the Court noted that with the
vast amount of data collected all of the
time, “police need not even know in ad-
vance whether they want to follow a par-
ticular individual or when.”g In Carpen-
ter’s investigation, the government was
able to “access each carrier’s deep re-
pository of historical location informa-
tion” “[w]ith just the click of a button.”h
This passive form of surveillance vastly
expands the power of the police.
Finally, the way the government collected information in Carpenter rep-
c 138 S. Ct. at 2216.
d These observations are adapted from E.E. Joh,
“Artificial Intelligence and Policing: Hints in
the Carpenter Decision,” Ohio State J. Crim L.
16, 281 (2019).
e 138 S. Ct. at 2219.
f 138 S. Ct. at 2218.
g 138 S. Ct. at 2218.
h 138 S. Ct. at 2218.
vastly expands the
potential pool of
people and activities
the police can watch.