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A Contender for "Most Scientifically Irresponsible Passage":
In his post below, Jonathan asks, "What is the most scientifically irresponsible passage in the United States Reports?" There are lots of contenders, but one nominee might be another contribution by Justice Scalia, footnote 2 in Kyllo v. United States.

  Kyllo considered whether pointing an infrared thermal imaging device at a home constitutes a "search" under the Fourth Amendment. Justice Scalia concluded that it did, it part because the device allowed the police to gather information about the interior of the home, namely, its temperature. In dissent, Justice Stevens argued that using the device was not a "search," in part because the device only revealed information about the exterior of the home. Justice Scalia responded to Stevens in footnote 2:
The dissent's repeated assertion that the thermal imaging did not obtain information regarding the interior of the home, post, at 3, 4 (opinion of Stevens, J.), is simply inaccurate. A thermal imager reveals the relative heat of various rooms in the home. The dissent may not find that information particularly private or important, see post, at 4, 5, 10, but there is no basis for saying it is not information regarding the interior of the home.
  Whether Scalia or Stevens had the better legal argument is debatable. But my understanding is that as a matter of physics, Scalia was wrong and Stevens was right. My research into this suggests that infrared radition is surface radiation: it emanates from surfaces, down to a depth of about 1/1,000 of an inch. See MIKE LLOYD, THERMAL IMAGING SYSTEMS 2-5 (1997). As a result, an infrared image only reveals the temperature of a surface, not the temperature of the space behind the surface. So the device really did reveal only the exterior temperature of the home, not the interior of the home.

  Of course, it is possible to draw reasonable inferences about the likely interior temperature of a home from the home's exterior temperature profile. Assuming a steady state system, we can make reasonable assumptions about how houses are usually built (for example, that there are no heat sources in the walls themselves) to find out information about the interior temperatures. But that information is only as good as the assumptions themselves. For example, if someone made a wall that had an good insulator and then a heat source on the exterior, the exterior would be hot even though that temperature would tell us nothing about the interior of the home.

  None of this necessarily means that Scalia was wrong as matter of law, of course, but I believe he was wrong as a matter of physics. That's my best sense, at least; I hope readers will let me know if I'm the one who is wrong here. (Of course, if it turns out that Scalia was right, I suppose I'll have to designate this "the most scientifically irresponsible blog post at the Volokh Conspiracy"...)
logicnazi (mail) (www):
No matter how good an insulater the walls may be eventually the radiation from the walls must match the black body radiation that would be given off by the interior of the home.

In other words so long as the interior of the home is giving off more infared radiation into the walls of the home than the walls of the home emit to the outside world the walls keep heating up. Eventually this process stabilizes letting one infer from the exterior radiation of the walls the amount of heat inside the walls.

Now sure their could be a heat source inside the walls as you say. However, this hardly proves anything. Scalia did not argue that the radiation directly eminates from the interior of the house.

Moreover, anytime we look at someone on the street the photons that hit our eyes have likely been absorbed and reemitted many times by air molecules in the interviening space. In fact I don't believe whether or not we are seeing the same photons as were initially emited from the person is even a sensical question to ask in QM.

Now of course whenever we see someone and infer they are wearing a green shirt this inference is only as good as our assumptions about the transmission of the light from them to us. In reality the image we see only reveals the photons incident on our detector from a certain direction not the photons that left their body. It is possible that someone has cleverly manipulated the air between them and us to create the illusion of someone with a green shirt.

However, if we want to retain any sense at all of the phrase 'reveals information' we say that looking at someone reveals information about what color clothes they are wearing regardless of the underlying physics of light propogation or remote possibility for being tricked. All that really matters is that this is a reliable way of determining the information at question not the means of physical transmission. That's just what the phrase means.
8.28.2006 1:47am
LTEC (mail) (www):
And when I look through your window, it's only the photons from outside your house that are actually hitting my eyes.

This debate reminds me of a chapter from Feynman where he complains about Orthodox Jews discussing the nature of electricity in order to settle some bizarre religious issue.

[OK Comments: LTEC, I believe Stevens agrees with your first point, which to him is why looking at something is not a Fourth Amendment search.]
8.28.2006 1:48am
Roger Schlafly (www):
If you want to take such a narrow view, then the image only reveals the infrared photons striking the detector, not the temperature of the surface. You have to make some physical assumptions in order to infer that the temperature of the wall is being measured.
8.28.2006 1:55am
OrinKerr:
LogicNazi writes:

So long as the interior of the home is giving off more infared radiation into the walls of the home than the walls of the home emit to the outside world the walls keep heating up.

I don't follow, LogicNazi. There are three kinds of heat transfer: conductive, convective, and radiative. Why would the infrared-length radiative heat transfer from the interior to the wall necessarily have to match the infrared-length heat transfer from the wall to the outside world? It's been 15 years since I studied these issues carefully, so maybe I'm just missing something, but I don't necessarily see that.
8.28.2006 2:04am
Dave Hardy (mail) (www):
Having a trifling exposure to this, but having spoken to specialists who have more ... indeed, it measures only the infrard photons reaching the detector. This is affected both by temperature and by radiance of the object. A black object does a better job of radiating than a whie one, for some reason I do not understand. An object can actually reach a temperature below ambient air temperatures under the right circumstances for the same reason.

But assuming that the walls of my house are roughly equal in radiance and in insulation, the infrared output of each room would be proportionate to the image. To the extent that they are not, what is the probative value of the IR image? It's introduced to prove a "hot spot," supposedly an area where the grow lights for marihuana plants are generating a lot of heat. If an IR glow is not proof that a room is quite hot, then probative value is zero. (And yes, at dinner time your kitchen is a hot spot. My specialist friend used it also for commercial buildings, to spot gaps in roof insulation and water leaks into it (viewed from his airplane).

I was in contact with an IR specialist, now dead, who regularly analysed police use of these devices, and was annoyed at how often police would image a house, find nothing probative, and then turn up the gain (brightening the image) until it looked very hot. The less smart ones would do it while the video was running, enabling it the manipulation to be seen. He said in the old days they'd do things like compare the electrical usage of the house to comparable houses around it, but had gotten lazy... now they just ran the license plates of cars parked at head shops, then imaged their houses, and juggled the video until it fit and gave arguable probable cause.

Technically, the fancier detectors (rarely used due to cost of machine and of operation ... it has to be cooled by compressed rare gasses) are photo buckets that count photons. The cheaper ones have tiny elements that measure temperature at each element. Both require lenses made of special glasses, since ordinary glass blocks IR of these wavelengths.
8.28.2006 2:15am
Rank Amateur (mail):
Since all information can only be apprehended through neurons, invasions of Fourth Amendment rights will always have some component that is exterior to a zone of privacy. The question that the case bumps up against seems to be: is the Fourth Amendment predominantly a procedural bar that looks to the extent to which the methodology used is (too?) invasive, or is it a substantive protection of unreachable zones of individual autonomy?
8.28.2006 2:29am
Lev:

As a result, an infrared image only reveals the temperature of a surface, not the temperature of the space behind the surface. So the device really did reveal only the exterior temperature of the home, not the interior of the home.


True, but that is not what Scalia said. According to your quote:


A thermal imager reveals the relative heat of various rooms in the home.


In a, shall we say, standard house, in a cold November in Vermont, if one corner room is a kitchen with a big fat Thanksgiving dinner being cooked in it with ranges and ovens a blazing, and another corner room is unused with the hot air register closed, then thermal imaging of the outside wall will reveal the relative heat of the two rooms. It will tell the observer that for some reason the one room is hotter than the other - information about the interior, hey, a search.

Thermal imaging will not, it is true, tell the actual temperature of the two rooms, it will only tell the actual temperature of the exterior walls on the other side of the two rooms' interior walls.

When Stephens says:


In dissent, Justice Stevens argued that using the device was not a "search," in part because the device only revealed information about the exterior of the home.


He is wrong. The device does not reveal the actual temperature of anything other than the exterior walls, but it reveals information about the relative temperatures of the rooms behind those exterior walls.

Check out House Detective on hgtv, website www.hgtv.com. They use thermal imaging devices aimed at walls to get information telling them whether and where water leaks are inside the walls from relative temperature differences of the outside of the walls.

The legal questions are: 1. is using the device a search for which a warrant is necessary because information about the inside of the house is actually obtained, and, 2. of course, does the device give the authorities any useful or meaningful information, ie probable cause, about what is going on inside the house.

[OK Comments: Lev, can you back up your claims? I bought an infrared thermal imager -- actually, it's less of an imager than just a point thermometer, but it works in the same way -- and it gives me actual temperatures, not relative temperatures. And your point about even relative temperatures seems to be subject to a host of assumptions about what is in the wall, how it is insulated, and the like. And as for your point 2, is that your personal take on what the legal issues should be? I'm not familiar with that in the cases.]
8.28.2006 2:34am
guest:
Dave Hardy: black objects absorb more light than white objects. Our eyes detect optical photons. Objects that don't produce their own optical light (the moon, Chamucos reposado, Orin Kerr) are seen because they reflect light - so white objects appear brighter to us than black objects. Because black objects absorb more light, though, they become hotter than white objects. Most objects that aren't stars (or lightbulb/fire-type things) emit much, much more light in the IR than in the optical, so the black object will appear brighter through the eyes of a Predator.

My guess here is that the bright lights that marijuana plants adore irradiate the walls as well. The walls of that room heat, and most of it would be emitted from those walls in the IR rather than being transfered to other rooms (NB, this is just a guess). I'm surprised that some people would think that IR, visible, and gamma ray (valuable to trace radioactivity) photons should be treated differently solely because of the photon's wavelength. It doesn't pass the sniff test.
8.28.2006 2:46am
Enoch:
I had a home energy audit a while ago, and one of the things he did was go over the interior and the exterior with a thermal imager. What the images revealed was nothing less than "information regarding the interior of the home", i.e. which parts of the interior were poorly air sealed and insulated.

Seems self-evident that a picture like this is conveying "information regarding the interior of the home":

http://www.ir55.com/images/1PDS2394820938409238402new-2.jpg

[OK Comments: Why is that self-evident, Enoch?]
8.28.2006 2:52am
guest:
For clarification, IR=infrared. Sorry for the use of the science lingo/abbreviation.
8.28.2006 3:11am
LTEC (mail) (www):
I was being ironic about the photons.

The point of my comment was that the physics distinction being discussed here is really theology, and not the right way to settle this issue. The issue should be settled by our legislators, based on a revised modern meaning of what "search" means, based at least in part on an understanding of why we are restricting searches in the first place.
8.28.2006 3:27am
Brian Garst (www):
Of what use would it be if it didn't reveal information on the interior? Seems to me Lev has it right.
8.28.2006 3:40am
Andrew Hyman (mail) (www):
The basic point is that, in the olden days, you'd have to trespass onto someone's yard in order to place thermometers on the outside of the house, and you'd also have to climb up the wall to monitor temperature on the second floor. Modern technology now allows the temperature at various parts of the house's surface to instead be ascertained from a distance, without stepping onto the yard. That was Scalia's point, and it's a good one.

And Scalia is technically correct that thermal imaging does obtain information regarding the interior of the home, by inference from the external information. A thermal imager does reveal the relative heat of various rooms in the home, as long as each of those rooms touches the outside wall.

[OK Comments: Andrew, you are of course free to adopt a "living Constitution" approach as a matter of law, but whast does it mean to say that as a "technical" matter you can make an inference that is often accurate? If you're making an inference that A suggests B, you're no longer technically getting B.]
8.28.2006 3:53am
Norman Yarvin (www):
Of interest is that thermal imagers do not see through windows; they only measure the temperature of the window glass.
8.28.2006 4:18am
Chico's Bail Bonds (mail):
Here is another way of thinking about it. If the device did not reveal information about the inside of the house, the police would not waste their time using it. The police have no use for something that only reveals information about the outside of a wall.

In Kyllo itself the thermal imager revealed information from inside the house, namely, that marijuana was being grown inside. The police in Kyllo didn't recieve divine inspiration that they would find marijuana in the house. The thermal imager told them.

[OK Comments: Why is that relevant?]
8.28.2006 4:30am
randal (mail):
You're making me defend Scalia? Ok, I'll bite.

Orin, physics (fortunately) has little to do with law. Scalia was correct in that the purpose and effect of the thermal imaging was to determine information about the interior of the home. You think the police were interested in the temperature of the exterior walls?

Why go to physics on this question? The Constitution isn't about photons.

{OK Comments: Randal, this post isn't about constitutional interpretation. It is about physics. Of course, you might think that the more interesting issues are constitutional ones, but that's just not the purpose of this particular post.]
8.28.2006 4:39am
zooba:
Actually, Stevens was correct, but in a semantic rather than scientific sense. The thermal imaging device only reveals information from the outside of the house - what photons the surface of the house is emitting. That information then gives rise to an inference about the relative temperature of various rooms. It is not the thermal imager or thermal imaging that "reveals information" about the inside of the home, it is the mental step of the LEO from seeing the exterior heat information that "reveals information" about the inside of the home. What SCALIA really means is that information about the inside of the house is inferable from using thermal imaging.
8.28.2006 4:55am
Ron Hardin (mail) (www):
The temperature of the exterior walls reveals the rate of energy consumption inside the house; and done by room, within each room, unless the house construction deliberately defeats it. (You could pump the heat into a geothermal sink and it wouldn't affect the exterior walls at all, or most simply use water cooling and drain the water as household waste. Whether this happens is one indication of an expectation of privacy being absent or not.)

Energy consumption is related to interior temperature by insulation. The more insulation, the higher the interior temperature for a given energy consumption. But in the case of the sought-after UV lights, it's not temperature that you want, but energy consumption, from which UV lights are inferred. Exterior temperature gives you this directly. Interior temperature is a red herring.

(If you have resistive electrical heating, you can leave on lights, TVs, computers for free in the heating season. A watt is a watt and it all winds up as heat. More TV just mean less furnace. Energy efficiency is pointless in the winter.
8.28.2006 5:50am
A. Zarkov (mail):
Does anyone think the theory of evolution has the same level of scientific certainty as (say) the special theory of relativity? The former theory has more assumptions, and relies more heavily on observational data. I personally think the theory of evolution is one of greatest scientific accomplishments of all time. But I would hate to see it presented as dogma.

When we teach relativity, we also teach Newtonian mechanics, and we tell the students where Newton went wrong with absolute time. I realize the analogy is somewhat flawed because Newtonian mechanics is approximately correct and easily co-exists with relativity. Not so for evolution and intelligent design which stand in contrast to one another. Of course, in a sense, so do absolute and relative time. Now does time exist at all? In the 1940s Godel demonstrated "rotating universe" solutions to Einstein's field equations, which seem to make time travel possible. But Godel says that if time travel is possible then time itself really doesn't exist. Einstein was quite disturbed that his field equations permitted something so bizarre as a Godel Universe. The point being there is always room for doubt about scientific theories and this includes the theory of evolution too. However, thus far it's holding up pretty well. So well, I use it as a guide on what to eat.
8.28.2006 6:47am
Chris Bell (mail):
Chico's Bail Bonds and zooba have it right, IMHO. Technically, the imager does not see into the home, it only measures the temperature of the outside walls. However, simple heat transfer equations can then tell you the heat inside the house.

These equations come straight out of textbooks, and will be correct unless the person has heated walls/some other tricking device. Therefore, we probably know information about the inside of the house.

Stevens is right, we aren't measuring the inside of the house. Scalia isn't far off, we are calculating probable information about the inside of the house.

[OK Comments: Chris, your point about "probably knowing" is the key, and explains why Scalia is wrong, I think.]
8.28.2006 8:22am
douglas (mail):
If a policeman walking down the street smells the odor of marijuana emanating from a window, is that reasonable search? He's discerning with his nose information about activities from inside the building. Why is smoke different under the law from IR waves? They both exist as real objects. What about sound waves? What if he hears people talking about their marijuana crop? Why should acoustic waves be treated differently than infrared waves? It's all wave energy, why the distinction under the law? I think Mr. Kerr is correct- the heat may be generated in the interior of the abode, but it migrates to the exterior. The fact that it can be interpreted to have an understanding of what is occuring in the interior is irrelevant scientifically. It's rather like the previously mentioned smoke, originating inside, and migrating outside. Where am I (not a lawyer) wrong here? This decision always really irritated me with it's pseudo-scientific legally convoluted justifications. Thanks, Orin, for putting some meat on the bones of my discontent.
8.28.2006 8:23am
Daniel Chapman (mail):
I'm not going to go re-read the case, but wasn't the point of Kyllo that the use of technology NOT IN COMMON PUBLIC USE can't be used to derive information about the interior of the home without a warrant? Didn't Scalia concede that if it ever became common for us all to walk around wearing IR sunglasses, then the police would be allowed to use the same technology to glean information that has been broadcast to the public?

Maybe when EVERYONE can see the thermal radiation of our home, we'll start taking steps to mask it. You know... to protect our privacy and all that. Then the cops can go ahead and use the information if we choose to broadcast it.
8.28.2006 8:42am
Daniel Chapman (mail):
After waking up a little, I suppose I should probably explain why my last post is relevant to the discussion... It's true that thermal imaging only reveals "external" information in a technical sense, but the only reason that distinction matters for Fourth Amendment purposes is to determine whether that information has been broadcast to the general public.

Does anyone REALLY think IR information is "public" at this point? Scalia didn't.
8.28.2006 9:11am
noahpraetorius (mail):
If indeed an infared imager only searches the outside of a home, there is no problem. If it searches the inside of the home there is a problem unless a warrant is obtained because the homeowner with closed window shades or in a location within the home where no one can see inside has a reasonable expectation of privacy. So Scalia may be wrong on the physics but is right on the issue.
8.28.2006 9:13am
Bill Sommerfeld (www):
douglas: I'm also not a lawyer.

As I see it, this case is about the impact of new technology on expectations of privacy. The Mk I human nose has been around forever, and just about everyone has a working nose; thermal imaging devices have not been, and not that many people have routine access to the devices. Maybe expectations of privacy would, over time, shift if every digital camera on the market had a thermal imaging mode..

Chris Ball: well, it depends on how you define measurement. Most measurements are indirect, not direct -- with a spring scale, you aren't directly measuring mass, but instead the change in length of a spring, which is proportionate to the force exerted by the local gravity field on an object, which is proportionate to the mass of the object. With the thermal imager, you're seeing the amount of IR emitted by each point on the surface of the home, which is affected by the exterior temperature, the structure of the house, and the location of any heat sources within the house.

Orin: In response to your question to Lev asking him to back up his claims:
Like a thermal imager, your IR thermometer measures the *actual* outside temperature of a spot on a wall. But it also lets you gauge relative *inside* temperatures: If there are two rooms behind the wall at different temperatures, the wall will most likely be warmer outside the warmer room, and cooler outside the cooler room, and the imager will directly tell you which room is warmer (but not by how much).
8.28.2006 9:15am
John (mail):
Scalia plainly is right. It's not photons we're talking about, but information. Suppose you had a sensitive microphone in your truck across the street and listend in on conversations. Are you listening to sound waves from in the house or sound waves outside the house? Why, you are just listening to the variations in air pressure (sound waves) at the truck! No eavesdropping here! Shall we ask whether electronic phone intercepts capture stuff from inside or outside (it might resolve a lot of NSA stuff people have been arguing about here)?

Scalia's point is that the capture of information from the house is what's important. Where the photons come from is is not. This makes sense to me.

[OK Comments: John, you're making a point about constitutional theory, right? That is, you're making a claim about what the law *should* mean? Note that my post is about physics, not law.]
8.28.2006 9:29am
plunge (mail):
Generally, when Scalia talks either science or history, we're in for a bad time. It's generally his weakest point (the law being his strongest).
8.28.2006 10:00am
Eric Rasmusen (mail) (www):
"John" asked about a sensitive microphone in a truck listening to conversations coming from an open window that couldn't be heard by someone without a microphone who was standing in the street.

Is that OK, under current law? (It should be, by Stevens, and shouldn't, by Scalia. Of course, for Scalia needing the mike shoudl be irrelevant-- it's a matter of whether you are learning about the interior of the house while standing outside.)

Here's another Scalia-killer. What if the police in Apartment 12A touch the wall with their hands, feel infrared heat, and realize that Apartment 12B is hot? Are they allowed to use that information? They have discovered something about the temperature of the inside of one room of Apartment 12B by using infrared emissions from it.
8.28.2006 10:37am
sksmith (mail):
Conceptually, Scalia is right. Scientifically, both are wrong.

As many have pointed out, the IR device doesn't measure the temperature of the inside of the house. And, as many have pointed out, it doesn't measure the temperature of the outside walls. It measures the photons that hit the surface of the IR device. Those photons are reacting to pressure from photons immediately behind them in the air, which are reacting to pressure from photons immediately behind them, which (if you repeat this a few million times) are reacting to pressure from photons on the surface of the house, which (if you repeat this a few million times) are reacting to pressure from photons emitting from a stove, or fire, or high intensity lightbulb in a room in the house. One could say, equally accurately, that an IR device is measuring the 'temperature' of a room in the house, of a wall in the house, of the insulation in the house, of the air in the yard, or of the glass on the lens of the IR device.
(Another analogy: imagine there is an explosion on a boat in the ocean. That explosion vibrates the boat enough to shake the water and create a wave. You are sitting on the beach and feel the wave with your hand. Did you feel the energy of the water at the beach, the energy of the water in the ocean between you and the boat, the energy of the vibration of the hull of the boat, or the energy of the explosion in the boiler room? The answer: Yes.)

Steve
8.28.2006 10:37am
Daniel Chapman (mail):
Eric Rasmussen: Unless they're feeling the front door, they'd need a warrant to do that.
8.28.2006 10:59am
PatHMV (mail) (www):
There are laser and other devices which, when aimed at a window, will detect and record the vibrations caused in that window by the voices of the people talking inside. Those vibrations transmit the speech of the individuals inside the house to the outside. No molecules are exchanged, nothing but information leaves the house.

Likewise, the information contained in the external IR readings comes from inside the house, even though the only physical molecules being measured are outside the house. Scalia does not say that the IR is measuring the molecules or photons inside the house, simply that it is revealing information about the interior of the house.

As for the bit about relative temperatures, it is quite correct that the IR is actually measuring the specific temperature of the top few molecules of the house. But the fact that the walls of one room are 95 degrees is meaningless. It conveys very little information of use to the police; perhaps all the walls of that house and all the houses are 95 degrees, because it's summer. But the fact that the walls of one room of the house are 95 degrees while the others are all 75 degrees, THAT is information, and that is what the police are measuring, by measuring the specific temperatures of the top few molecules of each part of the house.
8.28.2006 11:24am
Joel B. (mail):
I suppose this and Adler's post perhaps should be nominated for "most scientifically uncharitable post at the Volokh Conspriacy." Either way. I think this is one time it is important to distinguish between data and information. The data in Kerr's example comes from the exterior surface "up to a depth of 1/1000 of an inch." So the temperature reading comes from the "exterior surface." The thing is, as many of your readers have previously pointed out, is that Scalia is discussing information.

Putting the data on relative surface temperatures together, reveals information about the interior of the house, "assuming a steady state system," as you say. That information depends on assumptions, is extraneous and an irrelevant point. You assume that I'm writing this all in English, and so it should make sense. But what if I was really writing in Spanish, and just talking gibberish (I may be as it is anyway). Sure the conveyance of information depends on assumptions. That they depend on assumptions that are reasonable is what makes it better as opposed to worse information. (Such as that, yes I really am writing in English, or that, yes the house was not built with an external heat source built into the walls, and that the insulation is fairly even throughout the house.)
8.28.2006 11:46am
SeaDrive (mail):
I don't see that the thermal imaging is any different, scientifically, from using a pair of binoculars to look in the windows. In either case, a device is used to enhance the image formed from photons comming from the direction of the house. The homeownder could take steps to control the temperature of the walls, just as he could close the shades (though not as easily).

The real point is the legal one: cops are basically just looking for an excuse to enter the house and search, and can not be trusted not to cheat.
8.28.2006 11:46am
PatHMV (mail) (www):
Ok, so now I've read the opinion, and I have to say that I believe our host, Orin, has been most unfair to Justice Scalia. From the rest of the opinion, he makes it quite clear that he is very familiar with the intricate distinctions of, as he puts it, "off-the-wall" versus "through-the-wall" measurements. He just thinks it doesn't matter. As I (and others) have noted, it is quite possible to gain information about the interior of the house through measurements of the exterior of the house:

But just as a thermal imager captures only heat emanating from a house, so also a powerful directional microphone picks up only sound emanating from a house—and a satellite capable of scanning from many miles away would pick up only visible light emanating from a house. We rejected such a mechanical interpretation of the Fourth Amendment in Katz, where the eavesdropping device picked up only sound waves that reached the exterior of the phone booth. Reversing that approach would leave the homeowner at the mercy of advancing technology--including imaging technology that could discern all human activity in the home. While the technology used in the present case was relatively crude, the rule we adopt must take account of more sophisticated systems that are already in use or in development.3 The dissent's reliance on the distinction between "off-the-wall" and "through-the-wall" observation is entirely incompatible with the dissent's belief, which we discuss below, that thermal-imaging observations of the intimate details of a home are impermissible. The most sophisticated thermal imaging devices continue to measure heat "off-the-wall" rather than "through-the-wall"; the dissent's disapproval of those more sophisticated thermal-imaging devices, see post, at 10, is an acknowledgement that there is no substance to this distinction. As for the dissent's extraordinary assertion that anything learned through "an inference" cannot be a search, see post, at 4—5, that would validate even the "through-the-wall" technologies that the dissent purports to disapprove. Surely the dissent does not believe that the through-the-wall radar or ultrasound technology produces an 8-by-10 Kodak glossy that needs no analysis (i.e., the making of inferences). And, of course, the novel proposition that inference insulates a search is blatantly contrary to United States v. Karo, 468 U.S. 705 (1984), where the police "inferred" from the activation of a beeper that a certain can of ether was in the home. The police activity was held to be a search, and the search was held unlawful.4


I believe that it is time for the normally quite astute Mr. Kerr to redesignate this post...

[OK Comments: Pat, I believe you're confusing two different things. The distinction between "off the wall" and "through the wall" was not about surface radiation vs radiation from inside, but rather about active vs. passive measurement. Stevens was focused on the fact that infrared is passive measurement: it passively measures radiation that automatically emanates from surfaces. In contrast, other devices require active measurement, actually sending electromagnetic impulses to the place to be monitored and then making mresurements based on what happens to those impulses. Scalia rejects the passive/active distinction, but that doesn't address the exterior/interior distinction. That is, you can have passive measurement of the exterior or passive measurement of the interior.]
8.28.2006 12:48pm
DrObviousSo (mail) (www):
I suppose this and Adler's post perhaps should be nominated for "most scientifically uncharitable post at the Volokh Conspriacy."

Agreed. When most people lament the lack of scientific understanding in American, they are usually talking about creationism/evolution. I'm more bothered by demonstrably intelligent, educated professionals who don't understand the most basic implications of the most basic rules of thermodynamics (in this case), or Newtonian physics, econ, or computer science (not this case).
8.28.2006 12:55pm
Toby:
1) Assertions about black-body emanations being equal only describe the situation in equilibrium, when the black-box has consitent insualtion across its entire surface, when their are no paths between rooms, when the outside environemnt is also in equilibrium, not having changed recently [nightfall] and not having varying ability to transport emanted heat (wind on one side)

2) If anything detectable outside the house is fair game, what about the devices that can detect and replicate the view on a CRT-type computer screen from across the street, or can even read the data the disc heads pass over whether the computer is accessing them or not. (Hard now that disk have gotten so much faster) I think that anything that uses special miltary or NSA-grade equipment to pull off has gone from "reasonable" to "unreasonable" search.
8.28.2006 1:29pm
Fub:
Orin Kerr initially wrote:
So the device really did reveal only the exterior temperature of the home, not the interior of the home.

Of course, it is possible to draw reasonable inferences about the likely interior temperature of a home from the home's exterior temperature profile. Assuming a steady state system, we can make reasonable assumptions about how houses are usually built (for example, that there are no heat sources in the walls themselves) to find out information about the interior temperatures. But that information is only as good as the assumptions themselves. ...

None of this necessarily means that Scalia was wrong as matter of law, of course, but I believe he was wrong as a matter of physics.
Scalia actually wrote:
The dissent's repeated assertion that the thermal imaging did not obtain information regarding the interior of the home, ... is simply inaccurate. A thermal imager reveals the relative heat of various rooms in the home. The dissent may not find that information particularly private or important, ... but there is no basis for saying it is not information regarding the interior of the home.
Scalia's statement in boldface above is technically inaccurate due to insufficient hedging.

Obviously a thermal imager would not "reveal the heat of various rooms" to, say, a feral chimpanzee shivering outside the house against the winter cold and desparately seeking a warm place to stay. The chimp would not have benefit of intellectual training to make the inferences. But to a human with knowledge of what inferences are most probably correct (though not necessarily knowledge of why they are likely correct), and with absense of subterfuge or clever "rigging" of the house, the device would "reveal the heat of various rooms".

Scalia would have been more scientifically correct to say "To a properly trained observer, and in the absence of a clever subterfuge made by alterions on the house, a thermal imager reveals by straightforward inference the relative heat of various rooms in the home to a very high probability".

I think that even to those sensitive to misstatements about science, Scalia's actual assertion in this particular case is little more than a venial sin.
8.28.2006 2:12pm
wm13:
Well, if Scalia is scientifically illiterate, then my physics professor, who told us that absorption spectra reveal the chemical composition of stars, was similarly so. Obviously, absorption spectra only reveal the characteristics of the light emitted by the surfaces of stars. Any information about the chemical composition of the interiors of stars is based on inference. And my professor, like Scalia, entirely neglected to consider the possibility that aliens were planting devices on the surfaces to emit or absorb light at particular wavelengths.
8.28.2006 3:10pm
te (mail):
Perhaps a useful analogy would be the use of doppler stethoscope which can be directed at windows and records sounds coming from the other side of the glass via vibrations on the glass surface.

I think that many people would consider this invasive even though the microphone only records vibrations on the exterior of the glass.
8.28.2006 3:51pm
M. Sean Fosmire (mail):
There should be a recognized difference between a "scientifically mistaken" statement and one which is "scientifically irresponsible". The latter is a strong charge.

And as some have noted, Scalia was taking a common-sense rather than strictly scientific view: regardless of how the image is picked up, what it reveals is information about what is inside the home, and that is information that we normally expect to remain private.
8.28.2006 5:30pm
lucia (mail) (www):
Orin,

I'm going to take a liberty of suggesting an editorial revision:

For example, if someone made a wall that had an good insulator and then a heat source permitted the sun to shine on the exterior, the exterior would be hot even though that temperature would tell us nothing about the interior of the home.


In afternoons in late August, the brown colored siding the west facing wall of the first story of my tudor house is often hotter than the both interior of my house and the outside air. The siding remains warmer for several hours after sunset.

The white portion of the wall remains cool all day.

And yet the rooms upstairs -- behind the white paint -- are warmer than the rooms downstairs -- behind the brown siding. Who'd a thunk? :)

Unlike WM13's hypothetical aliens interfering with the spectral emmissions of stars, the heat from the sun is neither hypothetical nor negligible!
8.28.2006 6:45pm
PDXLawyer (mail):
Orin:

I think Scalia got it right as a matter of physics, as applied to law. It's true that the IR radiation the police sense originates on the exterior of the building. But, the temperature of the exterior of the building is driven mostly by what is happening in the interior of the building.

Perhaps a good way to understand it is by analogy to speech. When you and I are in a room and you talk, I "hear" you by sensing fluctuations in air pressure on my eardrum. Those fluctuations are caused by pressure waves which you generate, which we call "sound." The air acting on my eardrums is not the same air as the air into which you introduced the sound. The energy/information/sound traveled through the atmosphere without any substantial gross displacement of the conducting medium (air).

When you see something, photons (or radiation, if you prefer) come off the object you're looking at (usually reflected from some other source) and travel to your eye. In a perfect void, or over a short distance in a reasonably light-transmissible substance (like air) you can think of the photons going from the target to your eye relatively undisturbed. But, there is always some degree to which they are diffracted and/or absorbed and re-transmitted. You can still extract a pretty good amount of data even in the presence of a high degree of noise caused by this diffraction or diffusion. So, even when the photons hitting your eye are not the exact same photons which bounced off the target, (as would be the case in fog) you can still "see" to some degree.

The fact that the particular photon the cops detect "originated" on the surface of the wall does not mean take away from the fact that the signal which they are looking for came from within the house. The important thing for most purposes (including this one) is the signal, not the carrier medium. If the signal originated inside the house, then I think it is fair to say that the cops were "looking" inside.
8.28.2006 9:08pm
Lev:

[OK Comments: Lev, can you back up your claims? I bought an infrared thermal imager -- actually, it's less of an imager than just a point thermometer, but it works in the same way -- and it gives me actual temperatures, not relative temperatures.


Well, I don't have any idea of what you bought, but what they use on The House Detective sequences with Steve Ramos NoCal inspector fairly regularly, is a handheld video display thermal imager that when pointed at an interior wall that has been identified as possibly having a water leak, shows pretty pictures that show which areas are relatively cooler from water evaporation and relatively warmer from being dry. If there is no color variation and a "warm" temperature, the conclusion is no leak, yet. Maybe the colors represent actual temperatures, beats me, but the colors yield

information
about the

relative
temperatures inside the wall by receiving emanations and penumbras transmitted through the ether from the exterior of the wall to the equipment.


And your point about even relative temperatures seems to be subject to a host of assumptions about what is in the wall, how it is insulated, and the like.


And so what. Normally data are evaluated rather than accepted without question. That is my point number 2:

2. of course, does the device give the authorities any useful or meaningful information, ie probable cause, about what is going on inside the house.


And as for your point 2, is that your personal take on what the legal issues should be? I'm not familiar with that in the cases.]


I might ask, how does one get probable cause if one does not evaluate what data are available, if one accepts some one thing uncritically and by itself? And isn't that a, you know, legal issue - "based on the evidence available was there sufficient evidence to amount to probable cause such that a warrant, whether for search or arrest, should issue?" Isn't that what all that 4th amendment stuff about what is necessary to justify warrants is about?
8.29.2006 12:40am
eddie (mail):
How hard can this possibly be?

Scalia said: "A thermal imager reveals the relative heat of various rooms in the home."

Orin said: "[..] as a matter of physics, Scalia was wrong and Stevens was right."

To back up his assertion, Orin said: "[..] an infrared image only reveals the temperature of a surface, not the temperature of the space behind the surface."

The temperature of a surface depends, in large part, on the temperature of the space behind the surface. Using a thermal imager to observe that the surface of the walls outside one room are hotter than the surface of the walls outside another room yields the inevitable conclusion that the first room is hotter than the second room, i.e. it "reveals the relative heat" between the two rooms, in the same way that noting that a spring stretches further when one object is placed on it than when another is placed on it yeilds the inevitable conclusion that the first object is heavier than the second object.

To dispute Scalia's claim that "A thermal imager reveals the relative heat of various rooms in the home" is not to dispute the science behind thermal imaging but rather the philosphy of what constitutes "measurement" and "observation" and the linguistics of what the word "reveals" means - and to take a rather dubious position on both counts, I might add. This makes Scalia's words here a very poor candidate for being "the most scientifically irresponsible passage" in anything.

As a matter of physics, Scalia was right. As a matter of what Scalia said about physics, Orin was wrong. I have no idea whether Stevens was right or wrong as a matter of physics, because Orin declined to quote Stevens and I am declining to go look it up.
8.31.2006 12:41am