Back in 1983, the Supreme Court declared that "a person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another." That increasingly doubtful proposition underpins a nationwide network of more than 144,000 AI-assisted cameras that track the travels of innocent motorists across the country billions of times each week.
So far, state and federal courts have almost uniformly rejected constitutional challenges to automated license plate readers (ALPRs) installed by companies such as Flock Safety. But in a decision that could signal a shift in the legal treatment of Flock cameras, a federal judge in Oklahoma recently recognized that they enable "a type of indiscriminate mass surveillance."
ALPRs are much more sophisticated than the technology that the Supreme Court considered in 1983, when it approved the warrantless use of a radio transmitter that helped police tail a suspected methamphetamine manufacturer's car. Three decades later, by contrast, the Court said police should have obtained a search warrant before attaching a GPS tracker to another drug suspect's car.
The majority opinion in the latter case emphasized the physical intrusion necessary to install the tracker. But five justices embraced an alternative rationale, saying GPS tracking impinges on reasonable expectations of privacy by revealing potentially sensitive information about the target's historical whereabouts.
That theory came to the fore in a 2018 case involving mobile-phone location data collected by cell sites, which the majority said implicated the Fourth Amendment because "individuals have a reasonable expectation of privacy in the whole of their physical movements." The Supreme Court reiterated that principle this year, extending it to data collected by Google's Location History feature.
"An individual has a reasonable expectation of privacy in records about his cell phone's location," Justice Elena Kagan said in the majority opinion, "and police intrude on that constitutionally protected interest when they demand the information." By similar logic, U.S. District Judge Sara E. Hill concluded this month in the Oklahoma case, people have a reasonable expectation of privacy in ALPR records, and police therefore generally need a warrant to search them.
Those databases include "information about all vehicles that pass by any network-connected camera at all times," which police can peruse "on demand," Hill noted. "Freedom from persistent, dragnet-style surveillance while in public is not a foreign concept in our society, and it is a reasonable expectation that society already accepts," as reflected in the Supreme Court's cellphone decisions.
Like cars, cellphones "move in public places where people can see you in plain view," Hill wrote. "But it becomes constitutionally problematic when law enforcement can indiscriminately and passively catalog your whereabouts over an extended period of time and then use that information for any purpose whenever convenient."
At this point, Hill's decision is an outlier. "It appears that nearly every court examining the issue to date has determined that ALPR technology use is not a search under the Fourth Amendment because people have no reasonable expectation of privacy in their movements on public streets," she noted.
Last month, for instance, a federal judge in California held that ALPR database searches are "clearly distinguishable from and less extensive than the 'near perfect surveillance' achievable" with cell-site or Location History data. And the day after Hill's ruling, a state judge in California rejected a challenge to San Jose's Flock camera network, saying "there is no reasonable expectation of privacy in license plate data collected from cameras directed solely at public streets."
A federal lawsuit involving the same city's ALPR system, which the Institute for Justice filed last April, is still pending. So are challenges to Flock cameras in cities such as Wichita, Kansas, and Norfolk, Virginia.
Even when they reject such lawsuits, courts commonly acknowledge that the legal picture could change as the number and capabilities of ALPRs multiply. If so, it seems likely that Hill will eventually be joined by other judges who recognize the perils of "indiscriminate mass surveillance."
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