Andrew Guthrie Ferguson: How Smart Devices and Biometrics Are Eroding the Right to Privacy

Andrew Guthrie Ferguson, a lawyer and researcher of digital surveillance, describes an alarming shift: data that people voluntarily leave in smart devices and biometric systems is becoming easier and easier to turn into evidence for the police. The more services monitor our bodies, habits and movements, the less the familiar notion of private life holds up.

The Body as Evidence

Ferguson starts with a simple observation: smartwatches, fitness bands and medical gadgets know too much about a person. They record pulse, blood pressure, sleep, mood, menstrual cycle, sexual activity and dozens of other parameters. To the user, this looks like a handy self-tracking service. To investigators, it is a ready-made digital trail. If a device can show when a person slept, moved, felt stressed or stopped breathing, that data is potentially of interest not only to a doctor but also to the police.

The problem is especially acute in reproductive and mental health apps. The author notes that nearly a third of women in the US use cycle trackers, and these services collect not only dates and symptoms but also geolocation, information about partners and other sensitive details. Where abortion is restricted, such a trove of data can become a body of evidence. The same logic applies to online therapy services: information about depression, medication or crisis states may first go to advertising platforms and then become available to the state.

Where the Traces Are Collected

The problem long ago moved beyond apps. The FBI is building a huge biometric system, NGI, which stores voice profiles, palm prints, face templates, iris scans, tattoos and fingerprints. Separately, there is CODIS, a DNA database with 21.7 million profiles. Ferguson shows that the state and private companies are increasingly building infrastructure in which biological data is stored for years and later used far beyond its original purpose.

• In California, some defendants had DNA samples taken in exchange for having minor charges dropped.
• In New Jersey, newborn blood samples were kept for 23 years after screening.
• Police were able to request an infant's DNA to link his father to a crime from 15 years earlier.
• New methods make it possible to collect genetic material directly from the environment, without a separate blood draw.

"If a DNA sample is available, it will be used to build a case."

Errors and Loopholes

Facial recognition carries its own risk. The article offers two telling cases: in one, the system helped quickly identify a package thief from camera footage; in the other, it led to the false arrest of Nijeer Parks, who spent 10 days in jail even though he was not at the scene of the crime at all. The author stresses that even when a human formally remains "in the loop" of decision-making, the algorithm has already set the direction of suspicion. And if such tools are used even in minor cases, it is easy to imagine them becoming the standard for mass investigations.

The problem is that the law is poorly suited to surveillance on this scale. American privacy doctrine long assumed that a face, a voice or traces left in public are not truly shielded from the state. But in 1973 no one imagined that cities could be blanketed with thousands of HD cameras, linked into a network and made to match faces against police databases automatically. "Abandoned DNA" follows the same logic: if a person inevitably leaves biological material everywhere, they formally lose control over it, even though in essence it is the most intimate information there is.

What This Means

Ferguson's argument is not that biometrics and smart devices are useless: they do help treat people and solve crimes. His conclusion is different: without new legal limits, the convenience of digital services will increasingly be paid for with bodily and behavioral privacy. For users, that is a bad trade, because getting leaked biometric data back or dismantling a large-scale surveillance system is far harder than clicking "I agree" once.