The new Signal Trace system links mobile devices to license plates via roadside cameras. When a car passes a reader, the camera logs the plate while nearby Bluetooth or RFID signals are also captured. Over time, software can treat ، the same device as a recurring electronic signature tied to a vehicle.

Signal Trace, marketed by Leonardo, is designed to work alongside automatic license plate readers. The system recognizes groups of consumer devices that regularly move together, then associates them with plate records and time‑stamped locations. It can even identify a vehicle without seeing its plate, storing electronic fingerprints for later queries. While the product states it does not “identify people,” investigators can still link a device’s signature to other records, creating a name through association.

Privacy concerns echo past rulings such as Carpenter v. United States and the 2026 Chatrie decision, which affirmed that location data can reveal more than movement and constitute a Fourth Amendment search. Studies show that four time‑and‑place points can uniquely identify 95% of individuals, underscoring the risk of repeated proximity data.

Ultimately, Signal Trace shifts police focus from known identities to patterns of movement and association, raising questions about how much inference turns anonymous signals into actionable evidence.