Legal Tech • April 2025

The Whole of Their Movements

Authorities can search flock databases without a warrant.

Written by Pierre Grosdidier

In United states v. Martin, a Virginia federal district court held that authorities did not infringe the Fourth Amendment when they searched a Flock Safety (Flock) database without a warrant to identify a suspect.1 Flock systems are supercharged automated license plate readers.2 Flock Safety, a private company, sets up cameras at strategic traffic locations for clients such as police departments, schools, and homeowners’ associations.

The cameras record and store in databases vehicle pictures and identifiers such as license plate numbers, make, model, color, roof racks, body damage, and other visible objects, along with date, time, and geolocation stamps. Clients can network their databases, such as when a private entity grants access to its local police department. Flock systems operate around the clock but retain data for only a finite amount of time (here, 30 days). Moreover, the systems do not support searches based on human facial characteristics.3

Authorities in Richmond, Virginia, used store surveillance cameras to visualize an armed robbery suspect and his vehicle. The pictures showed a specific car model with a moonroof and characteristic rear window stickers but did not resolve the license plate number. At the time of the robberies, Flock maintained 188 cameras in and around Richmond. Authorities consulted a Flock database and pulled 2,500 responsive vehicle pictures, of which eventually three matched the suspect’s car. The database yielded the car’s license plate number, which allowed authorities to track down, arrest, and charge the suspect, Kumiko Martin Jr. At trial, Martin moved to suppress evidence, arguing that authorities accessed the Flock database without a warrant. He argued that the search “violated his reasonable expectation of privacy in the whole of his physical movements.”4

The court analyzed Martin’s argument under Katz’s two-part test, which holds that the Fourth Amendment protects a person who has a subjective expectation of privacy that society recognizes as reasonable.5 The court first held that Martin “had presented no evidence” to support his claim that he had a “subjective expectation of privacy.” Martin would have to show that he took steps to conceal his activities from public view and would have to overcome well-settled law that there “is simply no expectation of privacy in the exterior of one’s vehicle, or while driving it on public thoroughfares.”6

This first holding would have sufficed to deny Martin’s motion, but the court also analyzed Katz’s second element. It rejected Martin’s attempt to analogize Flock’s data gathering practices to those courts that have held required warrants in Carpenter v. United States and Leaders of a Beautiful Struggle v. Baltimore Police Department.7 In both these cases, technology tracked individuals sufficiently closely, including in private locations, that one could reconstruct the whole of their movements.8 These intrusions into private lives required warrants. The court held instead that the facts in this case were more akin to those in United States v. Chatrie, where the U.S. Court of Appeals for the 4th Circuit found no reasonable expectation of privacy in two hours of location history data, corresponding to a single errand, that Chatrie had voluntarily disclosed to Google.9 The data collection in Chatrie, as in this case, did not amount to a dragnet, as 188 Flock cameras captured only three pictures of Martin’s car in a 30-day window. This meager record could not allow authorities to reconstruct the whole of his movements. Thus, the facts did not support Martin’s reasonable expectation of privacy in his movements “within the reasonings of Carpenter or Beautiful Struggle.” The court also rejected Martin’s prediction that the proliferation of Flock cameras and database sharing will eventually create the dragnet that Carpenter and Beautiful People rejected. “The future is uncertain,” the court held, and these facts were not here yet.10

Notes

  1. No. 3:23-cr-150, --- F. Supp. 3d ---, 2024 WL

  2. 4476560 (E.D. Va. Oct. 11, 2014).

  3. SeePierre Grosdidier, Tracking Traffic: You Think No One Knows Where You are Driving? Think Again, 83 Tex. B.J. 656 (2020).

  4. Martin, at **1–3.

  5. Id. at **3–5.

  6. Id. at *5 (citing Katz v. United States, 389 U.S. 347 (1967) (Harlan, J. Concurring)). Id. at *11 (citations omitted).

  7. 585 U.S. 296 (2018); see also 2 F.4th 330 (4th Cir. 2021) (en banc); see Pierre Grosdidier, Big Brother? Aerial Surveillance Requires a Warrant, 84 Tex. B.J. 958 (2021).

  8. Cell site location information in Carpenter and aerial surveillance pictures in Beautiful Struggle.

  9. Martin, at **12–14 (citing United States v. Chatrie, 107 F.4th 319 (4th Cir. 2024)); see also Pierre Grosdidier, Courts are Split: A Look at the Constitutionality of Geofence Warrants, 87 Tex. B.J. 776 (2024).

  10. Martin at *14.

Headshot of Pierre Grosdidier who is wearing a white shirt, red tie, and black suit jacket.PIERRE GROSDIDIER is a litigation attorney in Houston. He is certified in construction law by the Texas Board of Legal Specialization. Prior to practicing law, Grosdidier worked in the process control industry. He holds a Ph.D. from Caltech and a J.D. from the University of Texas. Grosdidier is a member of the State Bar of Texas, a member of the Texas Bar Foundation, a fellow of the American Bar Foundation, and a registered P.E. in Texas (inactive). He was the State Bar of Texas Computer & Technology Section chair for 2022–2023 and was elected medium section representative to the State Bar of Texas for the 2023–2026 term.