A California Court of Appeals judge recently ruled in People v. Lieng that there’s no constitutional problem with police using night vision goggles to see things that they couldn’t otherwise see. In Kyllo v. United States the Supreme Court had ruled that police could not use a thermal imaging device without a warrant, and you’d think the same rule would apply here, but it doesn’t. The court’s two-part explanation for this is entertainingly bizarre.
Consider the first part:
Kyllo is inapplicable to this case. First, night goggles are commonly used by the military, police and border patrol, and they are available to the general public via Internet sales…More economical night vision goggles are available at sporting goods stores…Therefore, unlike thermal imaging devices, night vision goggles are available for general public use.
Scott Greenfield explains part of the problem with this reasoning in a post titled “The Amazon Exception.” (In this excerpt, Scott calls night-vision goggles “nogs” because someone told him that’s what all the cool kids are calling them.)
That nogs are used by the military, police and border patrol, fails to impress. Lots of technology is used by government agents. Much of it is used to do nasty stuff that would, in the absence of a warrant, violate the Constitution. So what?
But the kicker is that it’s “available to the general public via internet sales.” Now it’s getting interesting. When courts rely on the inventory at Amazon, or perhaps more obscure websites, for the scope of the 4th Amendment, there might be a problem.
No kidding there might be a problem. In this country, we supposedly have something called rule-of-law, which means we are not subject to the arbitrary whims and favors of despots and bureaucrats, but rather all people are held to a set of laws that are known in advance. But if the constitutionality of a search depends on something as vague as whether the tools used are “available to the general public,” then who can know what the law means? Almost everything is available to the general public if they’re willing to make some amount of effort, so who could possibly predict when a court might take notice?
Or as Scott says,
Rather than research the caselaw to determine whether police use of technology constitutes an unlawful search under the Fourth Amendment, we should begin our inquiry on Amazon. Is that the point?
Then there’s the second part of the court’s justification. Because I’m a science geek, I find it even more troublesome than the first part:
Second, state and federal courts addressing the use of night vision goggles since Kyllo have discussed the significant technological differences between the thermal imaging device used in Kyllo, and night vision goggles…Night vision goggles do not penetrate walls, detect something that would otherwise be invisible, or provide information that would otherwise require physical intrusion…The goggles merely amplify ambient light to see something that is already exposed to public view…This type of technology is no more “intrusive” than binoculars or flashlights, and courts have routinely approved the use of flashlights and binoculars by law enforcement officials.
The way this is written, the statement that “night vision goggles do not penetrate walls…or provide information that would otherwise require physical intrusion” seems to imply that thermal imaging does both of those things. As a matter of physics, that’s just not true. Thermal imaging cannot see through walls.
What thermal imaging can do is tell you the temperature of those walls, which may give you some idea of what’s on the other side. Put a heat source in a room, and the room will warm up. That will warm the inner surface of the room’s walls, and some of that heat will leak through the walls to heat the outer surface of the building. Then, like everything else in the universe that has a temperature, the outer surface of the building will give off electromagnetic radiation.
The spectrum of that radiation–the portion of energy given off at various frequencies–depends mostly on the temperature of the radiating object. Sufficiently hot objects–usually around 900 degrees F°–give off electromagnetic radiation at frequencies high enough for humans to see–visible light–and the object appears to be glowing a faint red. Objects that are even hotter will give off other colors of the spectrum until you see an even mix of colors, meaning the object glows white hot.
Cooler objects give off light (electromagnetic radiation) that has frequencies too low to be detected by the human eye. We call this light infrared, meaning “below red.” Infrared light behaves a lot like ordinary light, except that you just can’t see it. And, just like ordinary light, it can’t go through walls.
Getting back to the subject of this post, thermal imaging systems work by using electronic sensors to detect the low-frequency infrared light emitted from warm objects. The data from the sensor is used to create an image that is displayed to the user. Night vision systems, on the other hand, detect light that is in the visible part of the spectrum, but they use a sensor mechanism that can create an image from far less light than the human eye needs. Thus the main difference between the two technologies is that night vision works on light that is too dim for humans to see, whereas thermal imaging works on light that is the wrong frequency for humans to see.
That doesn’t seem like a distinction important enough for a constitutional right to hinge on, but it makes more sense than what the judge wrote.
On the other hand, perhaps because I think of this too much in terms of the physics, I’ve never had a clear understanding of the principles by which the courts have ruled that thermal imaging requires a warrant. Why should police need a warrant to examine energy emissions that a suspect is allowing to just radiate away? If the subject is standing in his house and yelling about his drug grow operation at the top of his lungs, should the police get warrant before they’re allowed to stand outside the house and listen? If not, then why should they need a warrant to detect infrared emissions outside the house?
If you don’t want people to know about your drug-growing business, you should control your infrared emissions. Don’t let your house radiate infrared energy through the air, where it could strike a sensor being held by a cop who’s sitting in his car on the street. You’re essentially sending signals to anyone with a receiver, so how is that an intrusion on your privacy?
Note that we can still rule out surveilance technologies that are intrusive–x-rays, penetrating radar, megnetic resonance–on the grounds that they involve sending something inside private property. They’re the logical equivalent of a cop standing outside your house and using a long stick to reach in a window and poke around in your belongings, which I assume would require a warrant just as if he had entered.
The basic distinction is that the police can use passive technology to monitor emissions passively, but they can’t actively send anything into an area they’re not allowed to enter themselves.
This particular way of thinking about surveilance methods draws a fairly bright line for law enforcement and the courts to follow, but I can think of at least three consequences which are probably worth thinking about.
First of all, as a libertarian, I’m very worried about how much surveilance this does allow. Not only does it allow an unlimited amount of passive surveilance in the visible and infrared bands, it also seems to allow a lot of sophisticated listening devices. (Sound is vibrations in air rather than electromagnetic radiation, but the same principles seem to make sense.) For example, sounds inside a building, including conversation, will leak out as very subtle vibrations which are normally lost in the noise. It’s theoretically possible, however, that an array of sensitive microphones and some very sophisticated signal processing technology could recover the original conversation.
Second, this rule would also allow police to listen to radio transmissions, including cell phones, without a warrant. I think I’m actually okay with this. Before the widespread use of cell phones, it was widely understood that everyone was legally permitted to receive any radio transmission they wanted to. After all, if other people transmitted radio signals in all directions, and some of those signals entered your house, it was pretty ridiculous to claim that tuning a receiver to pick them up was a violation of privacy. It was a simple concept that I’d like to see us return to: If you want privacy, don’t transmit your conversation to everyone within range.
Third, the rule against actively sending something into a private area would seem to rule out a police officer shining a flashlight into window of a building or even a car. That seems a bit ridiculous, even to me. In addition, it would lead to all kinds of ridiculous situations as the police try to work around it. E.g. what if the police officer wears a white windbraker jacket and his partner shines the patrol car’s spotlight on him–ostensibly to make sure he’s safe–causing reflected light from the jacket to shine in a window? Alternatively, if flashlights are allowed, then what about using an infrared flashlight to illuminate a scene for viewing with a thermal imager? This could turn nutty very quickly.
At this point, I kind of have to give up. I can’t seem to come up with a distinction that makes sense in terms of the physics involved and yet still offers adequate protection of privacy. Maybe the laws of physics are the wrong tools for figuring out things like this, or maybe vague and inconsistent rules made from case to case are the best we can do. I’d like to think that the law should make sense in terms of physics, but I’m not sure I have a good reason for believing that.