Privacy SOS

License plate readers, drones and the Katz test

Late last week the Congressional Research Service published a report, "Drones in Domestic Surveillance Operations: Fourth Amendment Implications and Legislative Responses." I haven't gotten a chance to read through the entire thing yet, but a couple of interesting things jump out right off the bat.

Among them:

  • License plate reading: The report mentions that drones can be used to read license plates, and cites a 2004 (!) Customs & Border Protection (CBP) web story, which reads in part: "UAVs are equipped with image recognition systems and sensors that can detect movement, read a license plate number, or even identify vehicle occupants from 15 miles away. Infrared sensors provide day and night imaging."
  • Face recognition: We know that drones are equipped with high powered, technologically advanced cameras. But the future beckons: "…organizations might seek to outfit drones with facial recognition or soft biometric recognition, 
    which can recognize and track individuals based on attributes such as height, age, gender, and skin color," the CRS report says.
  • Weaponization: "[A] sheriff’s office in Texas has recently acquired a 50-pound 
    ShadowHawk Helicopter that can carry a 40mm grenade launcher and a 12-gauge shotgun….The sheriff’s office denied that these lethal weapons would be used, but is reportedly contemplating use of rubber bullets and tear gas on their drones." 
  • Thermal imaging devices: The report describes see-through-the-wall technology that can be integrated with drones, linking to a manufacturer's website. (The sourced web page is not available to the public.)
These asides about the integration of other identification and spying tools with drone surveillance are integral to understanding the Fourth Amendment implications for such spying. The summary reads:
The touchstone of the Fourth Amendment is reasonableness. A reviewing court’s determination of the reasonableness of drone surveillance would likely be informed by location of the search, the sophistication of the technology used, and society’s conception of privacy in an age of rapid technological advancement. While individuals can expect substantial protections against warrantless government intrusions into their homes, the Fourth Amendment offers less robust restrictions upon government surveillance occurring in public places and perhaps even less in areas immediately outside the home, such as in driveways or backyards. Concomitantly, as technology advances, the contours of what is reasonable under the Fourth Amendment may adjust as people’s expectations of privacy evolve.  

A classic Fourth Amendment test in US jurisprudence is the Katz test, or the reasonable expectation of privacy test. It was established by the Supreme Court in a case about phone bugging and boils down to this: If the court thinks the general public believes it has a "reasonable expectation of privacy" in a given situation, the Fourth Amendment should protect whatever is disputed.

Do we have a reasonable expectation of privacy on a public street? Not when it comes to surveillance cameras, courts have ruled. But does that change when face recognition and advanced video analytics get thrown into the mix? Arguably, yes. 

The CRS report smartly addresses the Katz test in the context of drones and add-on technologies like license plate readers:

The crucial question, then, is whether drones have the potential to be significantly more invasive than traditional surveillance technologies such as manned aircraft or low-powered cameras—technologies that have been upheld in previous cases. In this vein, some have asked whether using sophisticated digital platforms on a drone is any different from attaching the same instrument to a lamppost or traditional aircraft. Take, for example, the tracking of license plates. Currently, many states and municipalities employ automatic license plate readers (ALPRs), which are usually mounted on police vehicles or stationary objects along the streets, take a snapshot of a license plate as a car drives by, and store this information in a large database for possible later use by law enforcement. It is alleged that these devices can be used to track a person’s movements when police aggregate the data from a multitude of ALPR stations. A majority of the reviewing federal circuit courts have held that a person has no reasonable expectation of privacy in his license plate number.
However, it appears that no federal court has addressed the constitutionality of the use ALPRs (whether attached to a drone, manned vehicle, or a stationary device), as opposed to plate numbers collected by a human observer. Nonetheless, the question remains whether attaching an ALPR—or any similar sophisticated technology—to a drone would alter the constitutionality of its use by law enforcement. Some say yes, arguing that the sophistication of drone technology in and of itself “present[s] a unique threat to privacy.” Drones are smaller, can fly longer, and can be built more cheaply than traditional aircraft. For instance, defense firm Lockheed Martin’s Stalker—a small, electrically powered drone—can be recharged from the ground using a laser. It now has a flight time of more than 48 hours. As this technology advances, it is reported that some drones could theoretically “stay in the air forever.” Unlike a stationary license plate tracker or video camera, drones can lock on a target’s every move for days, and possibly weeks and months. This ability to closely monitor an individual’s movements with pinpoint accuracy may raise more significant constitutional concerns than some other types of surveillance technology.  
Do drones change the surveillance and privacy equation? Do technologies like license plate readers attached to drones change that equation again?
These are crucial questions that Congress must seriously grapple with before our skies are populated with drones that can watch us for days, weeks or months, and use advanced technologies to track our movements like never before. Congressman Markey has circulated a draft bill that would provide necessary transparency requirements for agencies that want to use drones. Senator Rand Paul has introduced a bill that would require police to get a warrant to use drones for surveillance in most cases. And Representative Ted Poe's Preserving American Privacy Act of 2012 would require that law enforcement get a warrant to use drones for spying, as well as limit those warrant searches to felony cases.
These are important steps. As the CRS report observes, we are only seeing the very beginning of what the drone revolution has to offer police and federal agencies. The time is ripe to act for privacy now.

© 2021 ACLU of Massachusetts.