Sense-enhancing technologies

The term “sense-enhancing technologies” refers to all types of equipment or machines that increase the perceptual ability of the user. In practical terms, this means a device that allows the user to see or hear things that could not be detected by the use of the normal human eyes or ears: for example, infrared goggles, parabolic microphones, or thermal sensors. This entry will survey the different types of sense-enhancing technologies and provide an overview of the law governing their use.
Sense-enhancing technologies have been around for centuries. The first and most basic example of a sense-enhancing technology is artificial illumination, such as a torch or, in more modern usage, a flashlight. Another example is a visual magnifier, such as a telescope or binoculars, which have been used for centuries by scientists, law enforcement officers, and lay people in order to see things that would otherwise be undetectable by the naked eye. Hearing-enhancing devices can be traced back almost 200 years to devices like the stethoscope, used originally by doctors but also adapted for use by individuals conducting surveillance through walls.
As the twentieth century progressed, however, sense-enhancing devices became more powerful and more potentially intrusive in two ways. First, the potential magnitude of amplification increased dramatically: modern-day binoculars can magnify an image between 30 and 80 times its actual size, while an individual can use a parabolic microphone to listen in on a conversations over 400 feet away. Second, and more significantly, new devices have been created that can detect inputs that are beyond our five senses, such as x-ray devices, infrared light, and radiation. Sometimes termed “sense-replacing devices” rather than sense-enhancing devices, these surveillance tools have become ubiquitous in our society: metal detectors (which detect disturbances in a magnetic field) are a standard fixture in airports or any other “secure” location, while night-vision goggles and thermal imagers (which detect infrared light waves) are readily available on the open market and frequently used by law enforcement and military personnel. Other forms of sense-replacing devices, such as x-ray machines, are less widespread but commonplace in specific fields such as medicine. And still others have been used almost exclusively by law enforcement to great effect. Radar guns have been used by police for over 50 years to detect the speed of passing cars; today there are over 125,000 radar guns in this country, and an average motorist can expect to be monitored by a radar gun over 1000 times in his or her lifetime. Similarly, law enforcement officers use thousands of trained dogs throughout the country to detect the smell of narcotics or explosives; although technically these animals are not a type of “technology,” they are tools used to detect otherwise imperceptible sensory inputs during a search of an individual or an automobile. Finally, law enforcement officials are developing newer sense-enhancing (or sense-replacing) technology: handheld gun detectors are able to provide police officers with the shape and location of metal objects concealed on a person, while ion scans can be used on tables or the interior of automobiles to determine whether narcotics or explosives have recently been in contact with the surface.
The proliferation and increased effectiveness of sense-enhancing technologies have given rise to significant legal questions about whether and how to regulate them. As noted above, sense-enhancing technologies come in many different forms and can be used in many different ways, from everyday uses of commonplace items (such as pointing a flashlight down a dark alley) to specialized uses of more sophisticated devices (such as calculating the speed of cars with radar guns) to surveillance that intrudes quite dramatically into an individual’s privacy (such as detecting what a person is carrying under his or her clothes, or monitoring activities might be occurring inside the house). Legal regulation of these devices falls under two categories: first, the restrictions placed on law enforcement officials using these devices to investigate crime; and second, the restrictions placed on citizens using the devices for their own private purposes.
In the context of law enforcement, the primary question is a constitutional one: under what conditions (if any) is a government agent required to procure a search warrant before using sense-enhancing technology to conduct surveillance? Under the Fourth Amendment to the Constitution, a law enforcement officer is generally required to obtain a search warrant before conducting an intrusive search; in order to obtain such a warrant, the officer must prove to a magistrate that there is probable cause to believe that a suspect is engaged in illegal activity. If the magistrate agrees and issues the warrant, the officer can search the suspect, or the suspect’s home, automobile, or office, in almost any manner the officer wishes.
In the early stages of an investigation, a law enforcement officer might not yet have probable cause and therefore would not be able to obtain a warrant. Thus, many types of surveillance (with or without sense-enhancing technology) must be conducted without warrants, and courts strictly regulate what types of warrantless surveillance are permitted. For example, police officers can stake out a house and observe who enters and leaves, but they cannot enter the house without consent and search for contraband. Emerging technologies create a new spin on the old legal question: is a law enforcement officer allowed to conduct warrantless surveillance using sense-enhancing technology, and if so, what types of technology are permissible?
The Supreme Court addressed this question in the landmark case of Katz v. United States, 389 U.S. 347 (1967). In Katz law enforcement officers placed an electronic listening device on the outside of a public phone booth and eavesdropped on the defendant’s conversation. The defendant claimed that this surveillance method violated his Fourth Amendment rights, and the Supreme Court agreed. In the words of Justice Harlan, the electronic listening device violated the defendant’s “reasonable expectation of privacy,” and therefore law enforcement officers were not allowed to use such devices unless they first obtained a search warrant from a court.
The reasonable expectation of privacy test became the standard for evaluating the legality of sense-enhancing devices for the next 30 years. In evaluating whether or not a certain new technology violated this standard, courts would consider not only the type of technology at issue, but also the way in which it was used. For example, the Supreme Court held that using a homing device to track the movements of suspected criminals was legal if it merely reported the suspects’ travels over public highways, but using the same device to track their movements inside a private home violated the Fourth Amendment. Similarly, using a flashlight to examine a public area, a private open field, or even the interior of a car is permissible because such actions do not violate an individual’s reasonable expectation of privacy.
In 2001 the Supreme Court clarified the reasonable expectation of privacy test in the case of United States v. Kyllo, 533 U.S. 27 (2001). In Kyllo, government agents suspected the defendant was using high-intensity heat lamps to grow marijuana in his home. To confirm their suspicion, they conducted a scan of the house using a thermal imager, a device that detects infrared radiation. The heat patterns detected by the imager provided further evidence that the defendant was using heat lamps, and the agents used that information to acquire a search warrant. As in Katz, the Supreme Court held that the warrantless use of this sense-enhancing technology violated the Fourth Amendment, since the suspect had a reasonable expectation of privacy regarding the contents of his home. In so doing, however, the Court defined two different contexts in which the government’s use of a sense-enhancing technology would not violate an individual’s reasonable expectation of privacy and therefore could be permitted.
First, if the specific use of the technology only detected information that could otherwise have been obtained without physical intrusion into a private area, the surveillance was permissible, regardless of the type of technology used. In other words, if a law enforcement officer used a high-powered parabolic microphone to eavesdrop on a conversation that occurred in a public restaurant, the surveillance would be permissible. The information that the officer received from listening in on the conversation could have been acquired by other means without intruding into a private area (for example, law enforcement officers could place an undercover officer at the table next to the suspects to eavesdrop the old-fashioned way). Likewise, law enforcement officers would be permitted to use extremely high-powered binoculars to observe a suspected drug transaction in a park or on a street corner, since the suspects would be conducting their business in a public place and the activity could have been observed by any individual who was walking nearby. In other words, if the use of the technology merely allows law enforcement officers to more easily or more safely observe or detect things that they could have detected through more conventional means, the surveillance does not violate the Fourth Amendment. To put it another way, if the suspects are in a public place, they do not have a reasonable expectation of privacy regarding anything they say or do, even if law enforcement officers use the newest technology to spy on them.
Even if the surveillance does result in information that could not possibly have been obtained without physical intrusion into a private area, the government agents’ actions might still be legal. This is because of the second scenario set out by the Court: if the law enforcement officers are using a technology which is in “general public use,” they need not seek a warrant before conducting the surveillance. The term “general public use” was not defined in the opinion, and it will surely be the source of future litigation, but the general outlines were clear enough: devices such as flashlights and binoculars that are routinely used by the general public are in general public use, while newer, rarer technologies (such as gun detectors, which can see through a person’s clothing) are not. For example, assume law enforcement officers used a flashlight to look down a private driveway at night and saw two individuals conducting a drug transaction. Without the sense-enhancing technology of the flashlight, the officers could never have perceived the illegal activity unless they had entered the private property. But because flashlights are in general public use, the individuals in the driveway did not have a reasonable expectation of privacy regarding their actions. On the other hand, if the officers used a sophisticated, portable x-ray machine to see through the walls of a house, or a parabolic microphone to eavesdrop on the conversations inside a house, they would be using technology that is not in general public use to detect information that they could not possibly have acquired without a physical intrusion into the private house—and therefore that surveillance would be barred by the Fourth Amendment. This is exactly what happened in the Kyllo case itself: the Court decided that the thermal imager was not in general public use, and so it could not be used to gather information about what was going on inside the defendant’s private residence. Although some justices pointed out that the thermal imager used in Kyllo was widely available on the open market, with over 10,000 units already sold, a majority of the court held that such devices were not in fact in general public use—and probably because they were not yet in such widespread use that their ubiquity would change people’s reasonable expectation of privacy. If in the future, if everyone owned a thermal imager and they were routinely used by individuals (as flashlights and binoculars are today), then law enforcement officers could begin to use them with impunity, since in such a world the suspects they would be watching would have no objective reason to believe that the heat emanating from their homes or bodies is private information.
Compared to the well-developed (and well-litigated) standards governing the use of sense-enhancing devices by law enforcement officials, the laws regulating civilian use of those devices are relatively scarce and undefined. Every state has a common law right (that is, a right developed in the courts, not by statute) that protects individuals’ privacy, but most of the torts that are connected with that right involve the defendant giving publicity to the private facts in some way. The only applicable restriction in most jurisdictions is the common law tort of intrusion, which generally bars “invasive conduct which is highly offensive to a reasonable person.” Thus, a civilian who uses sense-enhancing technology in a way that is invasive and highly offensive would be liable for monetary damages in a civil suit to the person upon whom he or she was spying. At least one state has enacted a statute to deal with the specific problem of sense-enhancing technology: California bars any attempt to observe or detect “personal or familial” activities using a “visual or auditory enhancing device” (Cal. Civ. Code §1708.8(b) (2001)). As with the common law restriction, violation of this law merely subjects the defendant to civil, not criminal liability. The standard used by the California legislature for civilian misuse of these technologies closely mirrors the standard used by the Supreme Court for law enforcement officials: the use of the technology has to violate a reasonable expectation of privacy, and the information gathered must be of the type that could not otherwise have been gathered without physical intrusion onto private property.

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