Bartelt’s Dog and the Continuing Vitality of the Supreme Court’s Tacit Distinction between Sense Enhancement and Sense Creation

Last Term, in an amicus brief in United States v. Jones, 565 U.S. __, several colleagues and I highlighted the Supreme Court’s long, albeit not always clearly stated, history of distinguishing between sense-enhancing and sense-creating technologies for Fourth Amendment purposes.  As a practical matter, the Court has consistently subjected technologies in the latter category to closer scrutiny than technologies that merely bolster natural human senses.  Thus, the use of searchlights, field glasses, and (to some extent) beepers and airplane-mounted cameras was not found to implicate the Fourth Amendment.  As the Court explained, “[n]othing in the Fourth Amendment prohibit[s] the police from augmenting the sensory faculties bestowed upon them at birth with such enhancement as science and technology” may afford.  460 U.S. at 282 (emphasis added).  In contrast, the Court has held that technologies that create a new capacity altogether, including movie projectors, wiretaps, ultrasound devices, radar flashlights, directional microphones, thermal imagers, and (as of Jones) GPS tracking devices, do trigger the Fourth Amendment.  To hold otherwise, as the Court has stated, would “shrink the realm of guaranteed privacy,” leaving citizens “at the mercy of advancing technology.”  533 U.S. at 34-36.

In fact, of the landmark cases involving technology and the Fourth Amendment during the past 85 years (from United States v. Lee, 274 U.S. 559, in 1927 to Jones in 2012), only in one instance did the Supreme Court appear to deviate from this distinction between sense enhancement and sense creation.  In that case, United States v. Place, 462 U.S. 696, and its successors, City of Indianapolis v. Edmond, 531 U.S. 32, and Illinois v. Caballes, 543 U.S. 405, the Court held that the use of trained narcotics-detection dogs (more apparently similar to using a new capacity than merely enhancing a natural human sense) did not implicate the Fourth Amendment.  In our amicus brief in Jones, we rationalized Place, Edmond, and Caballes by arguing that dogs were unique, being natural biological creatures that had long been used by the police, even in the time of the Framers.  Further, we argued, a canine sniff, unlike the use of, say, a wiretap or a thermal imager, “discloses only the presence or absence of narcotics, a contraband item.”  462 U.S. at 707 (emphasis added).  Still, the apparent ‘dog exception’ was rankling.

The Supreme Court’s recent opinion in Florida v. Jardines, No. 11-564, clarifies those previous holdings by effectively limiting them to their respective contexts (“canine inspection of luggage in an airport” in Place and “canine inspection of an automobile during a lawful traffic stop” in Caballes).  See slip op. at 8 (emphases added).  Consistent with the notion that the use of trained narcotics-detection dogs is more akin to creating a new capacity than augmenting a human sense, the Court in Jardines declined to find Place, Edmond, or Caballes dispositive, instead analogizing the use of such dogs to the use of the (sense-creating) GPS tracking device considered in Jones.  Id. at 8-9.  As Justice Kagan, with Justices Ginsburg and Sotomayor joining, further explains, a trained drug-detection dog is “a super-sensitive instrument” comparable to the thermal-imaging device considered in Kyllo v. United States, 533 U.S. 27.  See Kagan’s concurrence, slip op. at 3-5.

As the Court states, the fact that “forensic dogs have been commonly used by police for centuries” is “irrelevant.”  Slip op. at 9.  And although dogs are “animal, not mineral,” “that is of no significance” to the Fourth Amendment analysis; “that the device is just a dog cannot change the equation.”  Kagan concurrence at 1-2, 4.  “Detective Bartelt’s dog was not your neighbor’s pet, come to your porch on a leisurely stroll,” Kagan continues.  Id. at 2.  Rather, “drug-detection dogs are highly trained tools … [t]hey are to the poodle down the street as high-powered binoculars are to a piece of plain glass.”  Id. at 2 (emphasis added).  Finally, in response to the dissent’s suggestion that since a “human sniff is not a search,” the use of a trained drug dog might be better viewed as a mere enhancement of the natural human sense of smell, Kagan reminds us that the Court already addressed that very same line of reasoning in Kyllo (where it rejected as “quite irrelevant” the suggestion that thermal imagers might be viewed as an enhancement of the natural human ability to “perceive, without technology, the heat of the home”).  Id. at 4-5 n.2 (internal citation omitted).

In short, three decades after dog sniffs were first considered by the Supreme Court, Bartelt’s dog has finally managed to put Place in its proper place and bury the sole apparent exception to the Court’s consistent distinction between sense enhancement and sense creation.

The author would like to thank Christina Mulligan for insightful suggestions which have greatly improved this post.

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14 Responses

  1. Orin Kerr says:

    I disagree with your reading of Jardines. On Pages 8-9, Scalia is not saying that dogs are like new capacity tools. Rather, he is saying that how you classify dogs is completely irrelevant under the trespass/physical intrusion test. As Scalia says, “[W]hen the government uses a physical intrusion to explore details of the home (including its curtilage), the antiquity of the tools that they bring along is irrelevant.” Unless I’m missing something, Scalia is just making about about the nature of the trespass/physical intrusion test, not a point about how to classify dogs.

    More broadly, I don’t think I understand your proposed difference between sense-enhancing tools and sense-creating tools. If a person’s senses gives them access to data A, and the addition of a tool gives them access to new information B, isn’t it arbitrary whether you say that the tool “enhanced” the senses (by giving a person access to B in addition to A) or “created” a sense (by giving them access to new information B)? Any time something small expands into something bigger, you can characterize it as an “enhancement” of the overall item or a “creation” of just the new part. Or so it would seem to me; can you help me understand what I’m missing?

  2. Albert Wong says:

    Orin – thanks for the feedback. The Court’s enhancement vs. creation distinction has always been tacit, and possibly not even entirely conscious. The terminology used has been inconsistent from case to case, and moreover, some of the cases have been decided under trespass and others under REP. It’s a mess. Despite the mess, though, what’s remarkable is that the Court, in practice, has had an essentially perfect record imposing Fourth Amendment limits on sense-creating technologies while leaving sense-enhancing technologies unchecked. That practical result is what I want to highlight.

    So that said, I agree that Scalia never explicitly says that “dogs are like new capacity tools.” He didn’t really come out and say that about GPS tracking devices in Jones either (although he did hint at it in footnote 6). Despite that, and despite the fact that Jones was decided under trespass and not REP, the practical end result was that GPS tracking devices, which are sense-creating, were subjected to the Fourth Amendment, consistent with the Court’s historical enhancement vs. creation record.

    In Jardines, Scalia analogizes the use of Bartelt’s dog here to the use of the GPS tracking device considered in Jones, and dismisses the difference in age between dogs vs. GPS tracking devices. As you note, Scalia wrote this to support his trespass holding, not to expound upon whether dogs create a new capacity. But the end result is that, for now at least, dogs are treated just like GPS tracking devices for Fourth Amendment purposes, antiquity notwithstanding. It’s possible that this may change in some future case decided under REP, where GPS tracking devices are subjected to tighter restrictions than dogs in certain situations due to the difference in antiquity. But that’s speculative.

    To your broader point, I agree that the line can be hard to draw at times. One of the earlier drafts of our Jones brief had “sense-enhancement” versus “sense-enhancement significantly beyond human capabilities” (instead of “sense-enhancement” versus “sense-creation”). In the former group are technologies that merely enhance the capabilities of an average human to that of a hypothetical “perfect” human. E.g., searchlights allow the average human to approximate the capabilities of someone with “perfect” night vision. In contrast, in the “sense-creation”/”significantly beyond human capabilities” group are technologies that confer senses that are completely superhuman; for example, no human, even one with “perfect” senses, would even begin to have the ability to perceive radio waves unassisted. Or see through solid walls. The line is, however, harder to draw in the case of certain technologies that don’t confer clearly superhuman senses like X-ray vision, yet still have the potential to enhance the capabilities of an average human to well beyond even that of a “perfect” human. The Court, for example, has suggested that airplane-mounted cameras might potentially be able to enhance vision so much in certain contexts that it might cross the line from “sense-enhancement” to “sense-creation.”

  3. Orin Kerr says:

    Albert, thanks for the response.

    As I understand it, your proposed distinction differentiates between “perfect” versions of powers that people do have and powers that no humans have. But this requires answering the level of generality at which you say that people have a particular power, which seems rather arbitrary. Take the example of night-vision goggles. Do night-vision goggles merely enhance the power to see at night, or do they give an entirely new power to see in the dark? You can reach either answer depending on how you choose to look at it. Further, a bit of googling suggests that there are two kinds of night-vision goggles available on the market these days. Here’s the summary from

    Image enhancement – This works by collecting the tiny amounts of light, including the lower portion of the infrared light spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that we can easily observe the image.

    Thermal imaging – This technology operates by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. Hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or buildings.

    Is your view that using the first kind of night vision goggle would not be a search but using the latter would be?

    As for your reading of the cases, it seems to me that you are imposing a theory on the cases that the cases do not support. Take your suggestion that “airplane-mounted cameras might potentially be able to enhance vision so much in certain contexts that it might cross the line from “sense-enhancement” to “sense-creation.”” I gather you are referring to Dow Chemical Co. v. United States, 476 U.S. 227 (1986). But Dow Chemical does not suggest a distinction between sense-enhancement and sense-creation. Rather, the discussion was focused on whether the surveillance revealed intimate details, the kind of details that might be observed in the context of the home. Here’s the passage:

    [T]he photographs here are not so revealing of intimate details as to raise constitutional concerns. Although they undoubtedly give EPA more detailed information than naked-eye views, they remain limited to an outline of the facility’s buildings and equipment.

    The key issue seems to me the nature of the information revealed — intimate or not intimate — rather than whether the tool used to obtain it enhances some existing power or creates a new power.

  4. Albert Wong says:

    Thanks Orin – this is a great discussion.

    I still think that for night vision, for example, it’s a fairly easy call. People can naturally see at night, some much better than others. Therefore, the use of glasses, “image enhancement” night-vision goggles, or other such aids by an average person is merely an enhancement of that person’s existing ability to see visible light. The call depends on the nature of the technology, not the name of the technology or the way it’s advertised. Thus, in your example, “night-vision goggles” that actually confer the ability to visualize infrared light – clearly a superhuman ability – are “sense-creating,” consistent with Kyllo.

    As for the cases, I don’t think they have necessarily turned on the nature of the information revealed. In Kyllo, for example, the Court dismissed as “quite irrelevant” the “fact that equivalent information could sometimes be obtained by other [non-thermal imaging] means.” And the Court also stated, in reference to Dow Chemical, that “[w]e have previously reserved judgment as to how much technological enhancement of ordinary perception … is too much.”

  5. Thanks for drawing my attention to the brief–I’m embarrassed to admit that I have not read it yet. I tend to agree that the intimacy of the intrusion matters more than the technology’s capability. The sense-enhancing vs. sense-creating distinction may just be an intimacy-dependent coincidence. The Court protects the home more than anywhere else in part b/c “houses” are mentioned in the 4th Am but also b/c the home is where our most intimate activities occur. The home, by (any reasonable) definition, necessarily has walls which people hide behind, and which, for now, can only be penetrated by a so-called sense-creating device (such as thermal imaging device) and not by a mere sense-enhancing device (such as search lights, field glasses and cameras). Thus, the court’s apparent hostility toward sense-creating devices may just be a hostility toward devices that can be used to spy on people inside their homes.

  6. Orin Kerr says:

    Albert, let’s take another example, that of GPS technology from Jones. I would think that is an obvious example of sense-enhancing technology. Every person has an ability to watch a car in public: Everyone can and does do that every day. Of course, the amount that they watch a car in public is limited by the fact that it is hard to follow the car around over time, but that’s just a question of difficulty rather than ability. In that sense, the GPS device enhances the senses by making it much easier to know the location of the car, just like the radio beeper in Knotts enhanced that ability (although not as much as a GPS device). But I gather you see GPS as an example of a sense-creating device? if so, why? What sense does it create?

    Re your final point about Kyllo, what’s the relevance of that point about equivalent means? I don’t see how it fits into your framework. And your point about the reference to Dow Chemical seems to cut against your theory, not with it: I thought your theory was that mere sense-enhancing is not a search, so the idea that sense-enhancing could be so great as to be a search would seem to cut against your proposed explanation.

  7. Albert Wong says:

    Orin – GPS tracking devices are “sense-creating” because they allow the “remote, automated collection of data about a target’s location, movements, and speed of movement.” Officers can simply sit back in the police station downtown – or, for that matter, the FBI headquarters on the other side of the country – and have the information come pouring in to their laptops. No unaided human has the ability to telepathically sense, in real time, the every move of someone on the other side of town. But this superhuman sense is exactly what GPS tracking technology confers.

    Unlike GPS, beepers function as an enhancement of, not a replacement for, naked-eye surveillance. Beepers make it easier for police to follow a vehicle through traffic by emitting, well, beeps that get stronger or weaker depending on whether police are getting closer or falling behind. Beepers can’t sense their own location, nor can they determine movements or speed of movement; they’re just a tracking aid. Think of how easy it would be to follow, for example, a bright pink Hummer through traffic. Now think of how much harder it would be to keep track of a nondescript gray sedan. A beeper simply makes following the sedan as easy as following the bright pink Hummer. In other words, beepers don’t allow anything beyond what a “perfect” human with great vision and good focus would be able to accomplish unaided.

    The “equivalent information” line from Kyllo was in response to your proposition that the “key issue seems to [be] the nature of the information revealed … rather than … the tool used to obtain it.” As for Dow Chemical, remember that I define “sense-creation” as including stuff that “enhance[s] the capabilities of an average human to well beyond even that of a “perfect” human.” In one of my previous replies, I suggested as an example that “airplane-mounted cameras might potentially be able to enhance vision so much in certain contexts that it might cross the line.” I cited to Kyllo to support that suggestion.

  8. Albert Wong says:

    Thanks Heidi! In response to your point about the “intimacy of the intrusion,” homes definitely receive the maximum amount of protection under the Fourth Amendment, relatively speaking. That said, I don’t think that theory entirely explains the Court’s sense-enhancement vs. sense-creation distinction. Several of the “restricted” sense-creating technologies either don’t implicate the home at all, or at least don’t necessarily implicate the home – e.g., GPS tracking devices, movie projectors, and even wiretaps. On the other hand, some of the “approved” sense-enhancing technologies certainly have the potential to diminish privacy in the home/curtilage, particularly at night – e.g., field glasses and searchlights. Also, the Court noted in Kyllo that it was “irrelevant” that “equivalent information could sometimes be obtained by other [non-thermal imaging] means.” This suggests that the means is important, not just the intimacy of the information obtained.

  9. Orin Kerr says:

    Albert, I think your answer brings me back to the problem I identified before: classifying a particular device as “sense creating” or “sense enhancing” requires answering a level-of-generality problem, and all you have to do to reach the answer you want is to play the level-of-generality game accordingly.

    In the case of GPS, for example, if you want to say that GPS devices are only sense enhancing, then you draw the level of generality broadly: You say that the issue is whether people have an ability to know the location of things which obviously they do. On the other hand, if you want to say that GPS devices are sense-creating, the you draw the level of generality narrowly. You say, as you did in your comment, that the issue is whether people have the ability to conduct “remote, automated collection of data about a target’s location, movements, and speed of movement.”

    You could do the same thing with night-vision goggles that work by image enhancement. If you want to say that they are sense-enhancing, then you draw the level of generality more broadly and say that the question is whether people have the ability to see at night. If you want to say that they are a sense-creating, however, then you draw the level of generality more narrowly and say that the issue is whether people have a the ability to see what is happening in the pitch-black night when no person can normally see.

  10. Albert Wong says:

    Orin – I think the same issue potentially arises in other contexts as well. But the issue does not, in itself, render a classification unworkable. For example, take natural-born U.S. citizens and naturalized U.S. citizens. It’s clearly possible to distinguish between the two, even though at a broader level of generality, they’re indistinguishable: people in both categories are U.S. citizens. Similarly, take U.S. citizens and permanent residents. Again, definitely distinguishable, but identical at a certain level of generality: people in both categories are lawfully present in the U.S.

    The issue here is essentially the same. The solution is to look at what the technology actually does, and compare it to the applicable biological human sense(s) – be it sight, hearing, taste, smell, touch, balance, and/or thermoception. The “ability to know the location of things” is not a biological sense. Nor is the “ability to see at night.”

  11. Orin Kerr says:

    Albert, I think the level of generality problem is important for two reasons.

    First, it raises serious doubts about whether the cases really follow the sense-creation/sense-ehancement distinction you suggest. In your post, you suggest that your theory has explanatory power because it unearths the “consistent distinction” that secretly explains all the cases. But if the distinction is infinitely malleable, then it’s hard to say that there is a consistent distinction. A finding of perfect consistency may just show that you can play with the distinction to create the impression of perfect consistency.

    Second, recognizing the level of generality problem suggests a need for a consistent theory of the proper level of generality to apply. Presumably courts shouldn’t just play with levels of generality to get to whatever answer they want in each case. Presumably, in interpreting the Constitution, there is some answer for how to choose the right level of generality – an answer that may lead to uncomfortable results (either in the need to overturn old cases or decide new ones) that may leads some to question the theory.

  12. Albert Wong says:

    Orin – I would agree that it raises serious doubts if fitting the cases to the sense-creation/sense-enhancement distinction required applying a different level of generality in each particular case. But that’s not the situation here. The comparison to biological human senses is an obvious and reasonable standard, and yields results consistent with all of the cases. I don’t see a need to artificially introduce a level of generality problem by playing around with the definition of the term “sense”.

    To your broader point, I concur that in other contexts, it has sometimes appeared that the level of generality applied was not clearly based on objective factors. I think this is where it can be helpful to consider what the Framers intended. See, e.g., Justice Thomas’ dissent in City of Indianapolis v. Edmond (concerning the constitutionality of a “program of indiscriminate stops of individuals not suspected of wrongdoing”).

  13. Orin Kerr says:

    Albert, I think the rub is that there is no “obvious” comparison to biological senses. When you make the comparison to biological senses, you are always implicitly choosing a level of generality to describe the relevant technology and only *then* comparing it to the human senses.

    Again, in the case of GPS, if you want to say that GPS devices are only sense enhancing, you say that the issue is whether the human senses give people the ability to know the location of a car. Obviously, they do. On the other hand, if you want to say that GPS devices are sense-creating, then you say that the issue is whether the human sense give people have the ability to conduct “remote, automated collection of data about a target’s location, movements, and speed of movement.” From that perspective, they don’t. In both cases, you are a making a comparison to the human senses. But by playing with the level of generality, you can pick the level as something so broad that the human senses give it or so narrow that they don’t. That’s my sense, at least. Thanks for the exchange.

  14. Albert Wong says:

    Orin – I think the appropriate analysis is to, as I stated above, “compare it to the applicable *biological* human sense(s) – be it sight, hearing, taste, smell, touch, balance, and/or thermoception. The ‘ability to know the location of things’ is not a biological sense.”

    In this case, the applicable biological sense is sight (and potentially, to some extent, hearing). GPS technology doesn’t enhance or improve sight or hearing. In fact, it doesn’t require one to use the senses of sight or hearing at all. What it does is add a telepathic sense, allowing one to sit back and (without seeing or hearing anything) just *know*, in real time, the every move of someone on the other side of town – or the other side of the country. I think it’s pretty clear. There is no level of generality problem because the comparison is to the relevant biological sense, not to some malleable concept of “what an unaided human could potentially determine without the use of the technology at issue.”

    Many thanks for the stimulating exchange.