The Mosaic Theory: Why Aggregated Public Data Is More Sensitive Than Its Parts

The **mosaic theory** holds that a collection of individually innocuous pieces of information can be far more sensitive than any of the pieces — so aggregation itself is a privacy harm, independent of whether each component was public. ## The intuition That you were at a particular junction on Tuesday morning is trivial. Where you were every minute for a month reveals your home, workplace, doctor, place of worship, who you spend nights with, and whether you attended a protest. No individual observation is private; the compiled pattern is intimate. The theory says the whole is categorically more revealing than the sum of its parts, which means a rule permitting each observation does not automatically permit their combination. ## In law The reasoning entered US constitutional law through location tracking. In *United States v. Jones* (2012) — 28 days of GPS tracking on a vehicle — concurring opinions argued that although any single public movement carries no expectation of privacy, prolonged aggregate tracking does. *Carpenter v. United States* (2018) extended this to historical cell-site location records, holding that accessing them was a search despite the records being held by a third party. The underlying shift is from asking *"was this individual observation private?"* to asking *"what does the compilation reveal?"* — which is a recognition that Practical Obscurity: The Privacy You Actually Have in Public was doing real work and that technology removed it. Related reasoning appears in freedom-of-information law, where compiled records of scattered public information are treated as more sensitive than the underlying scattered records. ## Why it applies to wearable cameras Any single frame from camera glasses is trivial — a person on a street, precisely what a passer-by would see. Continuous capture across a wearer's day, aggregated across many wearers, assembles something no bystander could: routines, associations, movements, and who was with whom. The aggregation argument is why "each individual recording is harmless" fails as a defence. It is structurally the same claim as "each GPS ping is a public fact", which courts have declined to accept. The tension the theory creates is real: it has no natural stopping point, and courts have struggled to say *how much* aggregation crosses the line. That is a genuine weakness. It is not a reason to treat the aggregate as equivalent to its parts.