Automated License Plate Readers, the Mosaic Theory, and the Fourth Amendment

The Massachusetts Supreme Judicial Court weighs in.

|The Volokh Conspiracy |

One of the fascinating questions raised by the United States Supreme Court's 2018 decision in Carpenter v. United States is how the Fourth Amendment applies to government use of automated license-plate readers (ALPRs) and the querying of ALPR databases.  Last week, the Massachusetts Supreme Judicial Court handed down what I believe is the first appellate decision on the question, Commonwealth v. McCarthyMcCarthy is likely the first of many appellate decisions on this question, so I thought it deserves a close look.

Applying the controversial mosaic theory of the Fourth Amendment, McCarthy ruled that use of ALPRs can violate the Fourth Amendment, but that it depends on how much the ALPR query happens to reveal.  Because the surveillance in this particular case was relatively limited, it did not tell the police enough to create a mosaic and was therefore not a Fourth Amendment search.

McCarthy is a fascinating case, although I think it's ultimately a good example of why the mosaic theory is unworkable and should be rejected (as I have argued here and here).  I'll start with the facts, turn to the majority's reasoning, explain Chief Justice Gants's concurrence, and then offer some thoughts of my own.

I.  The Facts

This is a drug case.  Investigators suspected McCarthy of distributing heroin from his home to a co-conspirator's home on Cape Cod.  There are two bridges on to Cape Cod, the Sagamore bridge and the Bourne bridge, and the state has ALPRs set up on those two bridges.  To see if their suspicions about McCarthy's travels were right,  the police set up an alert on the state ALPR system to tell the police when McCarthy's car crossed one of the two bridges.  The alert they set up operated in "real time," but only for the cameras fixed on those particular bridges.

For two and a half months, the police learned the precise dates, times, directions, and specific lanes that McCarthy's car traveled on the two bridges to or from Cape Cod.  The police then used a later ALPR hit to know when McCarthy's car had crossed one of the bridges and was likely meeting with his co-conspirator.  Upon seeing that meeting, the police made their arrest.

The legal issue raised in the case was whether the government violated McCarthy's constitutional rights by conducting this monitoring of his car's location.

II.  The Reasoning

The Supreme Judicial Court ruled that use of ALPRs can violate the Fourth Amendment, but that they didn't in this particular case.

The court began by endorsing the mosaic theory of the Fourth Amendment.  The SJC had previously suggested a mosaic theory was viable under its state constitution.  But here the court explicitly endorsed the theory for both the state constitution and (more importantly) the federal Fourth Amendment.

Looking at its state constitutional cases together with several federal constitutional cases, the court reasoned that

these cases articulate an aggregation principle for the technological surveillance of public conduct, sometimes referred to as the mosaic theory. When collected for a long enough period, the cumulative nature of the information collected implicates a privacy interest on the part of the individual who is the target of the tracking. . . . As the analogy goes, the color of a single stone depicts little, but by stepping back one can see a complete mosaic.

A detailed account of a person's movements, drawn from electronic surveillance, encroaches upon a person's reasonable expectation of privacy because the whole reveals far more than the sum of the parts. The difference is not one of degree but of kind.  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. Aggregated location data reveals 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.

(internal quotations and citations omitted, both here and in the passages below)

The court next concluded that use of ALPRs is a Fourth Amendment search if enough ALPRs are used in particular ways:

In determining whether a reasonable expectation of privacy has been invaded, it is not the amount of data that the Commonwealth seeks to admit in evidence that counts, but, rather, the amount of data that the government collects or to which it gains access. . . . For this reason, our constitutional analysis ideally would consider every ALPR record of a defendant's vehicle that had been stored and collected by the government up to the time of the defendant's arrest. That information, however, is not in the record before us.

With enough cameras in enough locations, the historic location data from an ALPR system in Massachusetts would invade a reasonable expectation of privacy and would constitute a search for constitutional purposes. The one-year retention period indicated in the EOPSS retention policy certainly is long enough to warrant constitutional protection. Like CSLI data, ALPRs allow the police to reconstruct people's past movements without knowing in advance who police are looking for, thus granting police access to a category of information otherwise [and previously] unknowable. Like both CSLI and GPS data, ALPRs circumvent traditional constraints on police surveillance power by being cheap (relative to human surveillance) and surreptitious.

So what's the test for when use of ALPRs is sufficient to trigger a Fourth Amendment search?

As I understand the court's opinion, the test is applied ex post.  After the surveillance has occurred, you look back and consider if the surveillance ended up revealing enough about a person's life to have been a search.  This should be evaluated based on the totality of the picture that emerged based on all of the circumstances:

[T]he constitutional question is not merely an exercise in counting cameras; the analysis should focus, ultimately, on the extent to which a substantial picture of the defendant's public movements are revealed by the surveillance.

For that purpose, where the ALPRs are placed matters too. ALPRs near constitutionally sensitive locations—the home, a place of worship, etc.—reveal more of an individual's life and associations than does an ALPR trained on an interstate highway. A network of ALPRs that surveils every residential side street paints a much more nuanced and invasive picture of a driver's life and public movements than one limited to major highways that open into innumerable possible destinations. For while no ALPR network is likely to be as detailed in its surveillance as GPS or CSLI data, one well may be able to make many of the same inferences from ALPR data that implicate expressive and associative rights.

So where is the line? Well, the court could not say exactly where the line is:

On this record, however, we need not, and indeed cannot, determine how pervasive a system of ALPRs would have to be to invade a reasonable expectation of privacy. While a testifying expert alluded to cameras "all over the State," the record is silent as to how many of these cameras currently exist, where they are located, and how many of them detected the defendant.

However, the court did conclude that the surveillance here was not enough:

[W]e consider the constitutional import of four cameras placed at two fixed locations on the ends of the Bourne and Sagamore bridges. . . .

There is no real question that the government, without securing a warrant, may use electronic devices to monitor an individual's movements in public to the extent that the same result could be achieved through visual surveillance. It is an entirely ordinary experience to drive past a police officer in a cruiser observing traffic on the side of the road, and, of course, an officer may read or write down a publicly displayed license plate number. In this way, a single license plate reader is similar to traditional surveillance techniques.

On the other hand, four factors distinguish ALPRs from an officer parked on the side of the road: (1) the policy of retaining the information for, at a minimum, one year; (2) the ability to record the license plate number of nearly every passing vehicle; (3) the continuous, twenty-four hour nature of the surveillance; and (4) the fact that the recorded license plate number is linked to the location of the observation. These are enhancements of what reasonably might be expected from the police.

The limited number of cameras and their specific placements, however, also are relevant in determining whether they reveal a mosaic of location information that is sufficiently detailed to invade a reasonable expectation of privacy. The cameras in question here gave police only the ability to determine whether the defendant was passing onto or off of the Cape at a particular moment, and when he had done so previously.

This limited surveillance does not allow the Commonwealth to monitor the whole of the defendant's public movements, or even his progress on a single journey. These particular cameras make this case perhaps more analogous to CSLI, if there were only two cellular telephone towers collecting data. Such a limited picture does not divulge the whole of the defendant's physical movements,  or track enough of his comings and goings so as to reveal the privacies of life.

That brought the court to its conclusion:

While we cannot say precisely how detailed a picture of the defendant's movements must be revealed to invoke constitutional protections, it is not that produced by four cameras at fixed locations on the ends of two bridges. Therefore, we conclude that the limited use of ALPRs in this case does not constitute a search within the meaning of either art. 14 or the Fourth Amendment.

(emphasis added)

III.  Chief Justice Gants's Concurrence

In a concurrence, Chief Justice Gants suggested that perhaps the mosaic theory should encompass multiple tiers of surveillance, with different degrees of surveillance possible with different court order requirements.  If surveillance is sufficient to constitute a search, he wrote, "we have two options":

Our first option is to determine based on the facts of a particular case when the locational mosaic of a targeted individual's movements crosses the threshold of the reasonable expectation of privacy. A mosaic above that threshold would require a search warrant based on probable cause, but a mosaic below that threshold would not require any court authorization.

Alternatively, we could strike a balance analogous to that struck by the United States Supreme Court in Terry v. Ohio, 392 U.S. 1, 21 (1968), and decide that there are two locational mosaic thresholds: a lesser threshold that may be permissibly crossed with a court order supported by an affidavit showing reasonable suspicion and a greater threshold that is permissibly crossed only with a search warrant supported by probable cause.

The reasonable suspicion standard would require "specific and articulable facts" demonstrating reasonable suspicion that the targeted individual has committed, is committing, or will commit a crime, and that there are reasonable grounds to believe that the data obtained from the query are relevant and material to an investigation of the crime.

Chief Justice Gants goes on to explain how this would work.  As I understand the proposal,  the government could apply for court orders for various levels of surveillance, based on its prediction of how much surveillance it will conduct and how much cause was needed for that level.  After the surveillance occurs, the reviewing court would assess whether it feels the government collected only a reasonable-suspicion amount of surveillance or a probable-cause amount of surveillance.  The court would then ask if the affidavit viewed ex post established ex ante enough cause to satisfy the mosaic demands of the surveillance that ended up occurring:

This second alternative would mean that law enforcement agencies would need to obtain court authorization more often before retrieving targeted individual historical locational information in their possession because queries that would not require a showing of probable cause might still require a showing of reasonable suspicion. But the benefit to law enforcement would be that, if the police sought a court order based on reasonable suspicion and a reviewing court determined that the query sought locational data that could yield a mosaic of movement requiring a showing of probable cause, the search would not be found unconstitutional (and the information collected would not be suppressed) if the reviewing court found that the affidavit supported a finding of probable cause.

In contrast, where no court order was obtained and a reviewing court determined that probable cause or reasonable suspicion was required to support the retrieval of historical locational information, the data retrieved from the query would have to be suppressed even if law enforcement could have met the applicable standard.

Under Chief Justice Gants's view, the tiered Fourth Amendment mosaic regime would also imply a government record-keeping requirement:

Regardless of which alternative the court ultimately chooses, a reviewing court will need to know the extent of the mosaic that was possible from the retrieval of historical locational information regarding the movements of a targeted individual, because only then can the court accurately determine whether the threshold had been crossed.

Therefore, unless the law enforcement agency has sought prior court approval to search for particularized locational data in its possession, the agency will have to preserve each and every search query for the retrieval of historical locational information regarding a targeted individual.

For instance, if the State police maintain 1,000 ALPRs at different locations throughout the Commonwealth, it matters whether they searched for a suspect's vehicle from the data yielded by all 1,000 cameras or only by four cameras, and it matters whether they gathered this data for one day or one hundred days. And regardless of whether a court authorized the search, the agency must preserve the historical locational data regarding a particular individual that the agency retrieved as a result of such queries from the data in its possession, even when that exceeds the amount of data that the agency uses in an investigation or at a trial.

Further, this Fourth Amendment theory also implies certain discovery obligations:

And the agency must make this preserved data and search request available in discovery when sought by the defendant. Only then will a court have the information it needs to determine whether the retrieval of locational information regarding a targeted individual crossed a constitutional threshold that requires court authorization and either reasonable suspicion or probable cause.

IV.  My Own Views

This is fascinating majority opinion and a fascinating concurrence.  The court offers a developed and engaged take on how the Fourth Amendment might apply to public surveillance.  I appreciate the Justices' engagement with some really deep questions.  In my view, though, McCarthy ultimately offers a demonstration of why the mosaic theory is unworkable.

The court's approach is to look ex post to see if the government learned enough about a person for the surveillance to need a warrant ex ante.  But the court can't say where the line is.  And that makes it hard both for the government to know what it should do and for reviewing courts to say when the line has been crossed.  Here, four cameras on two ends of two bridges for two and half months wasn't enough. In another case, the court says, a single camera "may well be" enough.  Who knows where the line may be?

This is the Fourth Amendment equivalent of Justice Stewart's comment about then-existing obscenity standards in Jacobellis v. Ohio.  "[P]erhaps I could never succeed in intelligibly" saying when a movie is unprotected obscenity, Justice Stewart famously commented. "But I know it when I see it, and the motion picture involved in this case is not that."

The McCarthy court's reasoning seems similar. Perhaps you can't succeed in intelligibly identifying when a search has occurred, but the court knows it when it sees it.  And surveillance "produced by four cameras at fixed locations on the ends of two bridges" is not that.

This is a particularly challenge approach given the likely need for a warrant if a search is later found.  After the data is collected, the appellate courts will then look at all the data, figure out what it revealed, and then say whether a warrant was needed before the government tried to collect it.

Think of how it would work with a query into an existing database instead of a real-time query like the one in McCarthy.  For example, imagine the government wanted to know where McCarthy's car had been for the last 10 days.  Maybe that query would reveal 10 hits from two cameras.  Or maybe that query would reveal 1,000 hits from 300 cameras.  If you're an officer, you can't know whether your query will reveal a "substantial picture of the defendant's public movements" until you know the results, at which time you can find out if you needed a warrant before you ran the query you just finished.  Or maybe more accurately, you'll then have the information needed to ask a judge whether the judge finds the picture "substantial" and therefore a search.  Odd.

To be clear, I don't have a particular view of how the Fourth Amendment should apply to ALPRs.  Maybe using them should be a search, maybe it shouldn't be.  But as I argued in this book chapter, Implementing Carpenter, I think the answer shouldn't rely on the mosaic theory.  The mosaic theory raises too many unanswerable questions to implement; it would keep courts and investigators guessing for years about what the law requires.

A bright-line answer is needed, I think. Maybe the bright-line rule should be that accessing ALPR data is always a search.  Maybe it should be that accessing ALPR data is never a search.  But I don't think it works to saying that it is sometimes a search, based on the totality of the circumstances depending on how things ended up going.

Other ALPR cases are pending, and it will be fascinating to see if they follow or diverge from the approach in McCarthy.  As always, stay tuned.

NEXT: Brickbat: Sandy Pants

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  1. Great post, thank you Prof. Kerr. Two nits, editorial issues; these sentences might be reworked:
    “The court here is offering developed and engaged take and how the Fourth Amendment might apply to public surveillance.”
    “This is a particularly challenge approach given the likely need for a warrant if a search is later found.”

    1. I think Professor Kerr, along with most of the rest of the bloggers on the web, are working on tight schedules, budgets and resources, so let’s give everybody blogging a pass Unless they are blogging about proper grammar.

      1. jj,
        I don’t think Publius was posting to make fun of the typos. I think it’s the only way (or, at least, the easiest and most convenient way) to let Orin know, so he can make the corrections. At older VC sites, I believe, there was an easy way to contact a VC OP directly and privately, which we all would be happy to do. Of course grammar or spelling mistakes slip through when blogging. The lack of an easy, private, way to contact blog writers is just one of the many many weaknesses of the Reason site. (lack of edit button, etc etc etc)

        1. thanks, yes, I was just trying to be helpful.

  2. I agree that a bright line should exist, as it will become not just whether a court thinks a search has occurred, but what a law enforcement officer or department thinks. We’ll end up with a wildly varying mosaic of thought across the country.

    Because of the existence of these databases, and no reporting or recording requirement regarding their access by LE (that I am aware of), millions of illegal searches can occur every day without anyone knowing; and LE can then take action against a suspect through other means without ever presenting this search to a court. LE can just “get lucky” all the time because their surveillance activities not bound by the 4th are previously informed by illegal searches. This is very dangerous to liberty.

    1. “Because of the existence of these databases, and no reporting or recording requirement regarding their access by LE (that I am aware of), millions of illegal searches can occur every day without anyone knowing…”

      First, there are recording requirements for ALPR in many states, often requiring deletion of the recorded information within a set period of time. As an example, Arkansas prohibits preservation of data for more than 150 days. This is, ostensibly, to protect the public from the purported privacy intrusion of long-term surveillance by ALPRs. How that squares with the concurrence’s theory (constitutional requirement of preservation so the court can make a determination later) is anyone’s guess.

      Second, you’re putting the cart before the horse. The entire problem with the mosaic theory is that it makes it functionally impossible for anyone–including law enforcement–to say beforehand what constitutes an “illegal search[]”. That doesn’t advance liberty interests, because it creates this massive grey area that we (the people) will only ever be able to figure out on the back end on a case-by-case basis, usually years after the purported violation of liberty occurred. Better to have a judicial bright line, even one that permits LEs to engage in a lot of pre-search surveillance, because then we can rein in the affronts to privacy legislatively, with certainty. There’s nothing stopping states from banning ALPRs by law enforcement today. Squishy legal tests defer public debate and policy-making unnecessarily. One of the practical benefits of bright-line rules is that they have a legislative bargain-forcing function.

    2. I think at the end of the day, if you want a bright line, it will probably need to be an equilibrium adjustment where the government has to get a warrant to search databases of information that were not available as of some arbitrary date.

      So any technology that, say, wasn’t available to law enforcement as of January 1, 1990, requires a search warrant.

      If you dislike that sort of a rule, I don’t see any alternative to the formless balancing Prof. Kerr doesn’t like under the mosaic theory.

      1. Personally, I’m glad that the police are generally much better at investigating crime than they were in 1990, and I’m very glad that they’re much, much better than they were in 1867 or in 1791. And when the police avail themselves of technological developments to do a better job, they don’t just benefit us by catching more criminals: they also do a better job of not charging innocent people. I don’t know why it would be a good thing to stop them from doing that.

        For instance, under your framework it seems like the police would need a warrant to use Google maps instead of an atlas? (Can they use paper maps that have been generated with new technology?) Obviously can’t use text messages—can they make phone calls on their smartphones, or do they have to find 30 year old cell phones until a warrant gets issued?

        I’m comfortable with a rule that limits Fourth Amendment searches to actual searches. Compiling public information simply isn’t a search, even if it ends up revealing a lot. If we want to restrict or condition law enforcement access to certain kinds of information, we can set up statutes that do that, as the federal government has with electronic service providers and wiretaps, and as several states have with respect to surreptitious recordings. Indeed, it appears that Massachusetts has regulated how the very technology at issue in this case can and can’t be used: those regulations just don’t require a warrant.

        1. ” I’m glad that the police are generally much better at investigating crime than they were in 1990″

          That’s not true, or at least if it is true it isn’t true in any way relevant to this issue.

          A technological innovation is not an improved investigation technique. Simply surveilling tens of millions of innocent Americans isn’t “investigation”. It’s the opposite of investigation.

          1. I’m not sure that it actually does change the meaning as you’re suggesting, but if you prefer, read “I’m glad that the police are able to conduct investigations in ways that produce more effective results”.

  3. Glossary:
    ALPR: automatic license plate reader
    GPS: global positioning system
    CSLI: cell site location information
    SJC: supreme judicial court
    EOPSS: executive office of public safety and security

    1. The EOPSS is also known as the Office of Public Safety, Security and Official Felon Finding, or OPSSOFF.

  4. The police then used a later ALPR hit to know when McCarthy’s car had crossed one of the bridges and was likely meeting with his co-conspirator. Upon seeing that meeting, the police made their arrest.

    Such a limited picture does not divulge the whole of the defendant’s physical movements, or track enough of his comings and goings so as to reveal the privacies of life.

    These two statements do not mix well.

    In any case, let’s look at the (possibly no longer proverbial) panopticons in China, Russia, or deep insode billion dollar NSA bilidings. With license plate readers, cameras with face recognition, hell, I’ve seen things on slashdot like automatic walking gate “fingerprinting” and vehicle tracking sans plate reading.

    All this feeding into a database where a government individual can type in your name and maybe home address and, presto! There is a report where you are right now.

    Rather than arguing why government should have this power without explicit grant, why not come in for the win of American constitutional design and realize it doesn’t.

    King George III would have used phone metadata to quickly round up the founding fathers and end the revolution, so the would have gated it behind warrants.

    Sto0 doing the heavy lifting for inevitable dictators by building tools or tyranny.

    1. Tools of. Please consider a 5 minute edit window. Speaking of slashdot, they stopped editing because trolls would post things to invoke angry responses, then go back and edit their troll posts to something else, to make the respondant look like an idiot. 5 minutes sounds about right for those who like to edit.

    2. “All this feeding into a database where a government individual can type in your name and maybe home address and, presto! There is a report where you are right now.”

      Law enforcement is allowed to stake out your location and follow you around (in public), today, without a warrant. They have as much right to be on the street as you do. A database will make this easier, but so what?

      “King George III…”

      Was not the elected government of the people who revolted against him. He also used a lot of things to suppress revolution that we like having (guns, boats, etc.).

      Why does every problem in society have to be of constitutional moment? If you don’t think the government should be able to keep such databases, or hang out on public streets, simple legislation can solve those “problems”.

      1. Law enforcement is allowed to stake out your location and follow you around (in public), today, without a warrant. They have as much right to be on the street as you do. A database will make this easier, but so what?

        The “so what” is what Prof. Kerr calls “equilibirum adjustment”. If you just draw analogies blindly between old time law enforcement techniques that were difficult and costly to modern techniques that are practically costless, you end up in a police state. So you have to adjust the equilibrium so that police don’t have appreciably more ability to surveill people than they had in the past.

        And that means constitutional limits on these technologies. We already have a couple of good examples of this happening (GPS, thermal imaging).

        1. “If you just draw analogies blindly between old time law enforcement techniques that were difficult and costly to modern techniques that are practically costless, you end up in a police state.”

          That’s what you and others have asserted. I don’t agree. Of course “police state” invokes subjective notions that I can’t really respond to without crawling into your head.

          If I don’t care about one cop sitting on a corner staking out a known suspect, but it can be done cheaper with a robot, I’d rather the robot. It’s strange for me to see other human beings complain about being surveilled wherever they go, when virtually everyone voluntarily submits their GPS location to third-parties every second of every day. And we do this voluntarily, because it wildly improves the conveniences and pleasure of life above and beyond any privacy interest you insist I had in Google not knowing that I’m in my home (or at work, or on the road). You need to convince me why I should care.

          But even if I did care, it doesn’t “end up in a police state” since law enforcement is bound by the rules we give them. I don’t need a judicial court order interpreting a 200 year old document. I just need an ordinary statute limiting some allegedly objectionable investigatory method. If I don’t want LE to use GPS or thermal imaging, I don’t need Kyllo or Carpenter. I just need a statute that says “law enforcement cannot use [technology] as part of any investigation.” Of course that statute scarcely exists, because nobody actually agrees with SCOTUS’s idiosyncratic views of what a reasonable expectation of privacy is.

          The “equilibrium adjustment” is a theory about how courts make decisions for people that they are fully capable of making without court involvement.

          1. You’re drawing bad analogies. We voluntarily submit our GPS location to third parties because we trust that they are using that information only for our benefit. (The fact that trust is severely misplaced is irrelevant.) Police surveillance, on the other hand, is never for the benefit of the person surveilled. The social contract is entirely different.

            Second, I have the option (however theoretical) to opt out of that sharing of my GPS information. I have not even the theoretical option to opt-out of police surveillance.

            It is inappropriate to try to compare the two situations.

            1. “We voluntarily submit our GPS location to third parties because we trust that they are using that information only for our benefit. (The fact that trust is severely misplaced is irrelevant.)”

              First, you’re not answering for me. I’m not laboring under the incorrect assumption that Google is using the information only for my benefit, since Google publishes that it uses the information for its own benefit. They also tell you they will give the information to law enforcement who ask for it, or at least reserve the right to do so.

              Second, to the extent there are gullible idiots who think Google receives their information–without charging them–and uses it only to enhance the user experience, the 4A doesn’t exist to give people privacy expectations they could never reasonably demand in the first place. Google (as an example) could not provide essentially free services without using “private” data voluntarily transmitted to it. There are service providers who, unlike Google, do promise to protect your information, but they charge money and for that reason virtually nobody uses them.

              Third, I don’t see how it could possibly be irrelevant to either the 4A or this discussion generally, that most people voluntarily hand over information to third parties. It speaks directly to whether any expectation of privacy is reasonable, or not.

              Fourth, and relatedly, the “for the benefit of the person surveilled” distinction strikes me as irrelevant. Lots of surveillance by Google is done not “for the benefit” of Google’s customers. When they in turn hand the information over to third parties, it’s exclusively for the benefit of Google and those third-parties.

              Finally, you do have the option of opting out of police surveillance. You shouldn’t go no public roads if you don’t want to be seen. The 4A has never been an affirmative promise that everything you do will be kept secret from everyone else. It’s a very narrow privacy right in your person, house, papers, and effects, and only against a subset of searches and seizures (the unreasonable ones), unless a warrant exists. The true fact in the world that you drove across a public bridge, where you could have been watched by anybody out there (including people who aren’t the police), is not your “person, house, papers, and effects”. The way you “opt out” of distributing that information is to avoid the public bridge. I (as a private citizen) wouldn’t need a warrant to record the license plates of cars traveling on a private road. And if you couldn’t stop me (under the 4A) why should you be able to stop the police?

              1. Third, I don’t see how it could possibly be irrelevant to either the 4A or this discussion generally, that most people voluntarily hand over information to third parties. It speaks directly to whether any expectation of privacy is reasonable, or not.

                It isn’t irrelevant, but this is why we need equilibrium adjustment. Because all of a sudden something that revealed only a little information about people now reveals a ton.

                Finally, you do have the option of opting out of police surveillance. You shouldn’t go no public roads if you don’t want to be seen.

                And at this point, you literally are saying you favor a police state. Do you understand what you are arguing? That anyone who goes out to do anything for any reason is consenting to 24/7 surveillance by the government. They can watch you that entire time, and, by the way, under Terry, if you do anything “suspicious”, the police can show up and stop and search you.

                You seem to be reacting to technology by saying “this is great! Now we can be East Germany”. Your ideas are scary.

          2. In addition to everything Rossami says, this makes no sense:

            But even if I did care, it doesn’t “end up in a police state” since law enforcement is bound by the rules we give them.

            You end up in a police state because no person should have the capability of watching everything that people do, at least absent some sort of good reason. This sort of wall-to-wall surveillance of ordinary citizens, whether you are talking about the Stasi, the KGB, or the fictional world of 1984, is exactly what people mean when they say a police state.

            And legislatures are not to be trusted, because, honestly, catching criminals has historically played much better than privacy in political contests. DA’s get judgeships and seats in the legislature because of their conviction percentages, not the number of people whose privacy they respected.

            I mean, why not repeal the 4th Amendment and leave this entire area to the legislature? You know the answer to that.

            1. “You end up in a police state because no person should have the capability of watching everything that people do…”

              They can’t watch what I do in my house. They can’t watch my papers. If I keep my effects in my house, they need a warrant to get at them. You’re free to believe that “no person” should get to watch everything you do, but they can legally do it, today, once you leave your house. And we don’t live in a police state. When you go out in public, people see you. You are volunteering information to those people, total strangers, every second that you waltz about in a grocery store.

              “…is exactly what people mean when they say a police state.”

              And yet, the trend every day of my life is people voluntarily trading more information with strangers, not less. Either the public is much more comfortable with your definition of “police state” or your definition needs refining.

              “And legislatures are not to be trusted…”

              The 4A is legislation.

              “…catching criminals has historically played much better than privacy in political contests.”

              Right, which says a lot about whether people care more about privacy than they do security. My observation is humans don’t care about privacy much at all.

              “I mean, why not repeal the 4th Amendment and leave this entire area to the legislature?”

              I actually like the balance the 4A creates, but I’m fine with repealing it, too. I certainly don’t think we should imagine what the ratifiers intended 200 years ago to answer the complicated policy questions you’re raising today. I’m not so confident that my balancing of interests is right that I think it should be decided that way. Why are you so confident?

              1. They can’t watch what I do in my house. They can’t watch my papers. If I keep my effects in my house

                So Katz was wrongly decided then? We should go back to an ultra-strict reading of the Fourth Amendment where it doesn’t protect generalized privacy at all, just house, person, papers, and effects?

                That’s just nuts. As I said, your ideas are scary. Repealing Olmstead and creating the Katz test was one of the most fundamentally good things the Supreme Court did in the last century.

                And even if you convinced me to read the Fourth Amendment this way, I would simply say that substantive due process and/or the Ninth Amendment protect generalized privacy and restrict police surveillance.

                1. Katz doesn’t change the outcome in the present case. You don’t have a reasonable expectation of privacy in the fact that you drive across a public bridge.

                  I’m ok with you calling my ideas “scary”. The idea that Katz is a doctrinal joke is something shared by prominent 4A scholars, including the OP, who once remarked that the Supreme Court’s “reasonable expectation of privacy” test is “widely considered an embarrassment” and a “failure”. If you think doctrinally jumbled and unjustifiable results are “fundamentally good” I think you’re just projecting your own policy preferences. The fact that you’ll search out for constitutional text that doesn’t address it, to justify your position, also suggests that you’re simply insisting on constitutionalizing your own views.

                  1. If you want to argue Katz used the wrong test, that’s one thing. (My understanding is that is OP’s position.)

                    But saying the 4th Amendment is limited to persons, papers, houses, and effects, is a nonstarter.

                    1. You brought up Katz. It has nothing to do with anything I said. But let’s stay there. Was the US a police state pre-Katz? If not, explain why.

            2. “You end up in a police state because no person should have the capability of watching everything that people do, at least absent some sort of good reason.”

              I tend to agree.

              My preferred line would be: don’t collect the plate reader locations at all w/o a warrant. So when someone reports their car stolen, or the kidnapping report comes in, or the police get a warrant because they suspect drug dealing, then and only then tell to the cameras start reporting the location of the specific plates involved.

          3. If I don’t care about one cop sitting on a corner staking out a known suspect, but it can be done cheaper with a robot, I’d rather the robot. It’s strange for me to see other human beings complain about being surveilled wherever they go, when virtually everyone voluntarily submits their GPS location to third-parties every second of every day. And we do this voluntarily, because it wildly improves the conveniences and pleasure of life above and beyond any privacy interest you insist I had in Google not knowing that I’m in my home (or at work, or on the road). You need to convince me why I should care.

            You just answered your own question. You should care because while giving the information to Google is (despite your subsequent caviling) for your benefit (it “wildly improves the conveniences and pleasure of life”), giving the information to the government is not.

            Google wants to use the information to sell you stuff (or let other people sell you stuff), which is good. The government wants to use the information to tax or imprison you.

  5. I disagree there needs to be a “bright line” and point out the difference between a cop on a street corner observing autos (maybe even taking notes), and a cop in a car following a specific vehicle.

    It’s the same thing with the ALPRs and as pointed out in the decision, if there were ALPRs set up everywhere that could almost completely track a person’s movements (like a cop in a car following someone), then that would requirement 6A processing.

    Now we could discuss the goodness/badness of electronic surveillance but that cat is out of the bag and it’s never going back in.

    1. I’m not following. Are you suggesting that there are constitutional limitations on a police officer’s ability to follow a specific vehicle?

      1. It’s not relevant to this discussion, but its worth noting there probably are some such limits even before we get into the issues with license plate readers. It would probably violate substantive due process for a cop to follow you around constantly with no law enforcement purpose merely to engage in voyeurism or harassment, for instance.

        1. Do you have some authority for that proposition? The doctrine I’m familiar with generally takes the opposite as pretty much axiomatic.

          1. I don’t have authority for it because there’s almost always at least a pretextual reason given for such conduct.

            But actually doing it for voyeurism and without any law enforcement purpose at all should “shock the conscience” under Rochin, for instance.

            1. The cases I’m familiar with don’t justify the police (for instance) deciding to follow a particular person by saying the officers’ hunches were enough: they justify them by saying that the police don’t need any justification to do so, because following someone isn’t a search. See, e.g., United States v. Knotts, 460 U.S. 276, 281-282 (1982) (“A person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another. When Petschen traveled over the public streets, he voluntarily conveyed to anyone who wanted to look the fact that he was traveling over particular roads in a particular direction, the fact of whatever stops he made, and the fact of his final destination when he exited from public roads onto private property.”).

              1. But I’m certainly not claiming to know everything: if you know of a case that would suggest there’s a difference, for fourth amendment purposes, between “a cop on a street corner observing autos” and “a cop in a car following a specific vehicle”, as apedad seemed to be implying, I’d certainly be interested to look at it.

          2. Just to be sure we’re on the same page: it’s OK if the mayor orders the local gendarmes to follow around his ex-wife, or his election opponent, or some reporter 24×7, with no suspicion of wrongdoing on the target’s part?

            1. I certainly wouldn’t call it OK: it would, for instance, be a good reason to vote against the mayor, or perhaps even to impeach or seek to recall him if the city charter contained a provision allowing that. Depending on the details, it could violate the first amendment or the equal protection clause, and it could perhaps even be criminal. But it wouldn’t be a fourth amendment search, and if the gendarmes (for instance) saw the target murdering someone, they could present that fact at a criminal trial.

            2. Of course we would object to a public figure using public resources for exclusively private benefit. It would be objectionable because we expect the police to investigate crimes, not follow around their bosses’ exes. We would need a new mayor.

  6. FYI — The domain name is missing in the link to the Massachusetts decision.

    Mr. D.

  7. It appears the engaged in active surveillance in real time. the same as posting a cop at the end of the street to see when a particular person is coming and going.

    that is different from saying, ‘Hey let’s see where this person has been coming and going from the last year’

    The real fear of surveillance is that the police will ask ‘Who has been going to and from these places’ use that data to find people and then make a case around that data to potentially imprison an innocent person

    Seems to me like a good decision that will become part of a framework of decisions that will eventually mean something…..

    1. “that is different from saying, ‘Hey let’s see where this person has been coming and going from the last year’”

      Well, you can’t watch someone over the last year without watching them in real time, either. I’m not sure the distinction you’re drawing is an important or interesting one. But it raises the precise issues that Professor Kerr is raising with this opinion, the mosaic theory generally, etc. Where is the line you are drawing? 2 days of surveillance? 3? 400?

    2. I don’t think I’ve seen a potential increase in wrongful convictions identified as a concern from privacy advocates, and I’m not sure I follow the reasoning. Surely getting additional accurate information about where people were makes it more likely that the police will correctly identify their targets, not less? (Which is not to say, of course, that there wouldn’t be other reasons why we nevertheless would want to keep that information from the police.)

      1. Requiring we get permission from the police and file a detailed travel application before we go from point A to point B would also, very likely, increase the accuracy of some criminal prosecutions.

        The notion that we are going to have less accurate prosecutions is literally built into the Fourth Amendment. It’s as obvious as can be that at least SOME illegal searches will disclose actual criminal activity, right? And yet we have decided as a society to endure this cost, because inaccurate criminal prosecutions are not the only way a criminal justice system can harm the populace.

        1. So you’re agreeing with Noscitur a sociis that we will have less accurate prosecutions.

          1. I am sure that ALL 4th Amendment enforcement leads to inaccuracies in the criminal justice system.

            But there’s a basic right here, and sometimes enforcing rights means the government doesn’t get to run at maximum efficiency.

            1. Of course, but the person Noscitur was responding to was arguing narrowly that we need the 4A to protect the innocent from being convicted. You’re agreeing that the 4A may lead to innocent people being convicted, but that’s a feature not a bug. And so y’all are agreeing.

              1. It’s not really a feature. My understanding is that a feature not a bug is something that is actually good, not bad.

                It’s more like a necessary evil. The only way to achieve the best possible accuracy in the criminal justice system is to utterly disregard privacy rights. And since that is a bad thing (or at least the framers thought so!), we don’t allow the criminal justice system to work at maximum accuracy.

        2. Hence my parenthetical. The justification I’m familiar with for conditio in police access to certain types of information is that it’s too intrusive for the police to be able to have it, or at least to have it without restriction. Unless I misunderstood, arpiniant1 was presenting a very different argument: that giving the police access to more information would make it more likely that innocent people would be wrongfully convicted (and that this was, in fact, the “real” reason to support these restrictions). That’s not an argument I’ve ever heard before, and I can’t say it makes a lot of sense to me. Hence my post.

          1. Well, if you assume the only two choices are the right person being convicted or the wrong person being convicted, maybe it doesn’t make sense. If you add in a third option of nobody being convicted, then maybe it does. The more information the police have, the more likely someone will be convicted, which means the more likely that both innocent and guilty people will be convicted.

  8. Whether it’s a bright line or a muddy one, the police need to be able to tell if it’s a search BEFORE they do it. Any ex post analysis is absolutely useless for providing guidance to the police on what they should be doing.

  9. I can think of a good bright line — let’s report to the public all the information about the cops and prosecutors and judges disclosed by each warrant.

    How many times did cops, prosecutors, and judges cross those particular bridges? Their personal family cars, not their government cars.

    I bet that would slow down usage of license plate data.

    1. Yes, I suppose if we imposed a personal cost on issuing warrants, we’d see fewer warrants issued. We could also simply assess all of the officials involved a personal levy of $10,000, or require them to be put in a stockade and whipped instead, which would have an even more significant deterrent effect.

      Why we would find this deterrent socially beneficial is not entirely clear to me, and seems like it would tend to encourage the police at the margins to seek evidence without applying for warrants as in this case, but it’s certainly possible.

      1. Because unlike arbitrary fines or physical punishment it is precisely calibrated to any dignitary injury or loss a hypothetical “reasonable man” would suffer under the rules.

        1. 1. The evidence collected pursuant to a warrant isn’t released to the public;
          2. In many cases, there’s no clear way to analogize the items sought in the warrant to similar items from the judge, prosecutor, and police officers;
          3. This proposal still offers no guidance ex ante as to whether a particular inquiry is or is not a fourth amendment search.

          So It doesn’t seem “precisely calibrated” to do much other than incentivize more warrantless searches of the kind at issue here, which doesn’t seem like the result you’re interested in.

  10. I don’t necessarily have a problem with ex post analysis, so long as the agencies involved are tracked on every single “search” and are subject to lawsuits and criminal investigation (by an independent organization) whenever it is determined that the search was unconstitutional. (And that the subjects are given timely and sufficient notification to initiate such suits or complaints when appropriate.)

    And no, this will never happen of course. Which should act as a pointer to what I think of the underlying issue.

    1. You don’t have a problem with not letting the police know in advance whether or not their conduct is legal, as long as there are extremely heavy consequences if they guess wrong?

      Can’t see any problems there!

      (Also, what happens if the independent organization that investigates the police for gathering too much information itself gathers too much information so as to have conducted an illegal search? Do we get another independent agency to investigate them?)

      1. That scheme seems to work well enough when the government is applying it to individual citizens, so I don’t see why it shouldn’t work when applied to government employees as well.

        Although I suppose there might be some way to immunize the employees from liability. Perhaps we could call it a “warrant” and make it conditional upon prior approval by a judge.

        A radical proposal, to be sure.

  11. The mosaic theory does have its difficulties. But the alternative argument that this kind of surveillance deserves no protection at all is much, much worse.

    I think the better answer would have been to say that this level of recording needed a warrant. If you want a bright line, accessing ALPR data should always be a search.

    I would further amend the rules about warrants to say that the results of this particular surveillance can be used ONLY for this case. That adds a necessary control that prevents the police from using overlapping warrants that might be individually justifiable to create an unconstitutional database to be used against the rest of us. Yes, that implies overturning the third-party rule. I see that as a feature, not a bug.

    1. “I think the better answer would have been to say that this level of recording needed a warrant. If you want a bright line, accessing ALPR data should always be a search.”

      If this were the rule, why wouldn’t the police also need a warrant to physically place an officer on the bridge to watch for the suspect’s car? Or to stakeout the suspect’s house? (Maybe you think the police should require a warrant for that, too?)

      1. Because the practical requirements to post a couple of officers (allowing for bathroom breaks, eating, and sheer boredom) on the bridge, in each direction, with binoculars and cameras provide an entirely natural obstacle to widespread searches of this type. I bet you can’t find a single example of such searches.

        May as well ask why no court has ever ruled on using Zeppelins to hover over a house with cameras, or posting officers at every intersection with notepads, or opening every single letter at every single post office.

        1. “Because the practical requirements to post a couple of officers (allowing for bathroom breaks, eating, and sheer boredom) on the bridge, in each direction, with binoculars and cameras provide an entirely natural obstacle to widespread searches of this type. I bet you can’t find a single example of such searches.”

          Of course. We could also place other limitations on law enforcement’s ability to surveil the public, like banning them from leaving the office, or requiring them to only hire people in wheel chairs, or limiting the number of officers to 1 per 1,000,000 residents. But why would we do that? If it isn’t objectionable for a police officer to stake out my house without a warrant, why should we care if it is done more efficiently (and cheaply, for the public fisc) by a robot?

          “…to hover over a house with cameras…”

          Well it can be done with the naked eye. California v. Ciraolo 476 US 207 (1986); Dow Chemical Co. v. United States 476 US 227 (1986); Florida v. Riley 488 US 445 (1989). Why do you think it should be different if cameras are used instead?

          “…or posting officers at every intersection with notepads…”

          This is already legal, without a warrant. There are no 4A limits on law enforcement’s ability to stand at public intersections with notepads.

          “…or opening every single letter at every single post office.”

          Well they can’t do that without a warrant, Ex parte Jackson 96 US 727 (1877). There are narrow exceptions, like exigent circumstances or letters to other countries (19 USC 1583(a)(l)). But the exceptions are narrow.

          1. I guess you missed the part about “practical requirements”, and indeed, my entire argument. I;m not sure what you are responding to or what your response means.

            1. The purpose of the arbitrary limitations on policing methods (“banning them from leaving hte office, or requiring htem to only hire people in wheel chairs”) is to show that while these could become “practical requirements” but it would be stupid for the public to want to employ them. But maybe you agree that we should employ these hurdles?

              “I;m not sure what you are responding to or what your response means.”

              Hmmmm. For this conversation to continue you are going to need to explain to me why you’re not acting intentionally fucking dumb. If you pose hypotheticals (“May as well ask…”) am I to assume in the future that you aren’t interested in the answers? Can I take your response as a confession that you aren’t a serious person?

          2. It is objectionable for a police officer to stake our your house without a warrant. The fact that we don’t currently require a warrant for that activity does not make it normatively right.

            1. Why do you think I should find it “objectionable”?

              1. Oh, it’s very clear that you don’t find it objectionable. From your comments, it’s not clear that you would find any degree of police power objectionable. You seem entirely comfortable with a lack of privacy. The rest of us commenting here disagree. It is objectionable. If a private citizen did it, we’d arrest them for stalking. No cop, on his/her authority alone, ought to be able to convert criminal behavior into legal behavior.

                1. Stalking requires the intent to cause fear in the victim. Otherwise you would be able to sue private investigators. Or strangers on the street who looked at you.

                  1. a. Depending on the jurisdiction, no, “intent to cause fear” is not always an element of the crime of stalking. In fact, I would venture to say that your subjective intent is almost never an element. Actually causing fear in a reasonable person is a common element, though. See, for example, the many prosecutions of jilted lovers who are successfully prosecuted despite saying that their intent was love, devotion or some other positive emotion.
                    b. Even in jurisdictions where fear is a necessary element, a police stake-out meets it. At least, based on the relatively low standards of “causing fear” that courts have supported in non-police settings. The fact that police have mixed motives should be as irrelevant as the fact that jilted lovers have mixed motives.

                    1. The purpose of a police stakeout is to avoid being noticed by the person observed. If successful, it can’t be stalking, because it can’t cause fear (unless noticed). Even in those jurisdictions that do not require intent to cause fear, the prosecution still has to show an intent to commit the act that resulted in fear. If the stalker’s intent is to remain hidden, and for none of his behavior to be observed by the victim (as is the case in a police stakeout), even that intent requirement cannot be met.

              2. Why do you think I should find it “objectionable”?

                Well, you should care about privacy. If you do, then you would find it objectionable. Therefore, you should find it objectionable.

                If you simply don’t care about privacy, then there’s no way to convince you, because that’s the answer.

          3. If it isn’t objectionable for a police officer to stake out my house without a warrant, why should we care if it is done more efficiently (and cheaply, for the public fisc) by a robot

            Because it is objectionable. So we want it done rarely. So we don’t want it to be cheap.

            This is already legal, without a warrant. There are no 4A limits on law enforcement’s ability to stand at public intersections with notepads.

            But there are financial limits, which ultimately lead to the same result as 4A limits. So we don’t have to worry about it. But if you eliminate those financial considerations, then we do need to worry about it, and need to find another way to keep police from doing that. (I’m just restating the equilibrium adjustment argument here.)

  12. Here is a suggested bright line. A search begins whenever law enforcement’s attention fixes on a particular person in the absence of that person’s presence. Everything done after that to gather information about that person is done pursuant to a search, and requires a warrant.

    Note that a cop on the beat, or by the side of the road, is still free to engage his reasonable suspicion based on whatever he sees happening. But that suspicion must rely only on contemporaneous observation, not on any prior particularized law enforcement intent—which is what occasions the need for a warrant.

    Thus in the license plate case, the cops can still search the database after the fact, to discover the suspect’s movements, but they need a warrant, and that warrant will not be able to rely for its validity on the movements being searched for.

    That bypasses the mosaic theory, I think, for cases like this one. But it may also leave the mosaic theory in place for different kinds of cases to which it may be applied with fewer complications—such as cases involving mass surveillance (or group surveillance) without particularized suspicion.

    1. I generally think you are full of statist nonsense, but that’s an amazingly simple solution, which of course will never find favor with any government official. Thank you for that. I still object to collecting all that data in the first place, simply because the idea of government agents not looking at the data is naive beyond measure.

    2. The police are investigating a murder. The victim had a planner with him, and the last entry (several hours before the body was found) says, “meeting with Stephen Lathrop”. It’s your contention that the fourth amendment precludes the police from getting any more information about you?

      1. Yes — absent a search warrant.

        1. At least as I understand it — I don’t want to misrepresent Stephen Lathrop’s interpretation. But that is what I understand, and I approve.

          1. Can they look in the contacts section of the planner to see if there’s contact information for Stephen Lathrop? Can they search his name in google? Can they ask nearby pedestrians if they are Stephen Lathrop?

            (Without a warrant, I mean, since they wouldn’t be able to obtain one.)

            1. Why wouldn’t they be able to obtain a warrant based on this information?

              1. What would the search warrant be for? If a murderer happens to have my name in his contacts, do you think this should allow the police to search my house? On what basis?

    3. The rule you proposed is not “bright line” at all. “[Not based] on any prior particularized law enforcement intent” is worse than the mosaic theory. And it encourages LE to go to the most intrusive searches as quickly as possible, as opposed to trying to build a case for a warrant through less intrusive measures (like stakeouts).

      Any proposal that will not allow police to engage in what virtually everybody has come to accept as routine police work, is not going to survive in practice. If you don’t give police the opportunity to develop facts they need to secure a warrant, before a warrant issues, the rules for warrants will be relaxed. And since warrants authorize a lot, pushing LE to warrants as quickly as possible will lead to more invasions of privacy, not less.

      1. “has come to accept” == no bright line whatsoever, in that it keeps moving to whatever some judge or cop thinks is appropriate now.

        1. NToJ isn’t proposing that the Fourth Amendment standard should be that techniques that have come to be accepted as routine are permissible: they’re making a point about what would happen if your proposal were to be put into effect.

          For instance, in my murder hypothetical above, the police pretty clearly don’t have probable cause that Lathrop committed the murder, which means that they shouldn’t be able to get a warrant. Instead, we’d expect them to use less intrusive investigatory techniques to learn more about Lathrop, which they would then use to establish probable cause to allow for warrants to conduct searches that required them.

          But society isn’t ever going to accept that, when a name comes up like that in a murder investigation, the police can’t (for instance) try to look up his phone number or run his criminal history or ask if anyone saw him at the time of the crime. So if you’re going to say that the police need warrants to take those steps, the predictable result is a watering down of what judicial officers consider probable cause—which in turn means that you can expect to see police get more intrusive warrants more quickly with less evidentiary support.

          1. That’s why my bright line (above) is a better one. Police can use any technology that was available without a warrant as of 1/1/1990 (or some other arbitrary date). Any technology developed after that requires a warrant.

            1. So in my hypothetical, the police wouldn’t be able to do a google search for Lathrop. They wouldn’t be able to run his criminal history, unless they used a legacy system that was more than 30 years old, in which case it would be fine. They could try to arrange a meeting with him by email, but not by text message, and certainly not with a smartphone. And if he was willing to talk, they couldn’t use Apple Maps to try to find the meeting place.

              There’s some fuzziness at the margins (do they need to use a 30 year old phone to make calls, or is it okay to use a phone that was made more recently? Is it okay if the phone has some features that weren’t available 30 years ago as long as they don’t use them? What if the phone networks at the police station have been improved or modified?) but I will agree that it is reasonably clear. Incredibly stupid, but clear.

              1. No, they could run his criminal history. Just because the computers were updated doesn’t mean the technology has changed any.

                Text messages are not searches.

                You are interpreting my test in the worst possible faith. In the real world, courts would interpret my test and would give it a reasonable construction.

                1. Well now you’ve lost me.

                  Text messages and the license plate cameras at issue in this case are both tools the police can use to make their investigations more efficient. If we’re going to use the ad-hoc “does this feel like a search to me” inquiry being advocated in this decision and the concurrence, I agree that using text messages to coordinate and communicate will rarely add enough to make judges feel like something has transformed into a fourth amendment search. I thought you were proposing a bright line rule: if the police use any technology invented after your cutoff date, then that’s a fourth amendment search. Now it seems that your line isn’t so bright after all: some information gathering won’t be a search after all, even if the police do use the forbidden technology. Can you clarify how you would expect a judge to make the distinction, and how the police officer is supposed to anticipate whether a warrant is needed before using technology?

    4. Here is a suggested bright line. A search begins whenever law enforcement’s attention fixes on a particular person in the absence of that person’s presence. Everything done after that to gather information about that person is done pursuant to a search, and requires a warrant.

      I guess that’s a bright line, but it’s a nonsensical one that relies on a failure to understand what a warrant is.

      There’s not a high standard to obtain a search warrant, but there is a standard: probable cause. How are the police supposed to develop probable cause to obtain a warrant if they aren’t allowed to find out any information about a person?

      And how is it a search to, say, ask someone’s neighbors or co-workers about that person’s activities?

  13. Presumably this ALPR system is for tolling. And drivers have a reasonable expectation that the system will be otherwise private information.

    So why isn’t the question, “why NOT require a warrant”? Why is the question always “how do we find an excuse to allow this?”

    1. No, it appears that these cameras were specifically deployed by the police for law enforcement purposes.

  14. Without reading through all the other comments, my two cents say we should err on the side of freedom and liberty. Therefore, the bright line should be that it’s always a search.

    This should apply to every form of surveillance. From a flatfoot spending shoe leather to an NSA system reading my texts. Everything requires a warrant.

    1. Well, I have to concede that “the government always loses” is a bright-line rule.

      1. Noscitur, if there is a standard for getting a warrant—whatever the standard may be—and the government does not meet that standard, and does not get the warrant, why is that a loss? If the government stands for justice according to law, wouldn’t frustration of an unjustified warrant application be a win for government, and not a loss?

        Perhaps you have narrowed your view of government inappropriately, to include only law enforcement officers.

  15. This sort of tracking is similar to what Apple and Google are proposing to due with cellphone tracking or tracing to measure the spread of the coronavirus. They claim that the information will be anonymized by disconnecting specific cellphone users from their cellphones and phone numbers. I call this a slippery slope issue and the path to using the cellphone data for other purposes is significant. How would the cellphone data be used and for what purpose, and could the data be de-anonymized later. The federal government needs to speak clearly on this matter to clearly regulate in a way to protect citizen’s rights.

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