Cell Tower Dumps and Geofence Searches (United States Attorney's Office, District Of Maryland)

To Whom It May Concern:

Pursuant to the Maryland Public Information Act, I hereby request the following records:

Materials related to "cell tower dumps" and "geofence" searches as used by this agency in the performance of its responsibilities.

By "cell tower dump," or just "tower dump," I mean the practice of requesting cell phone service providers to disclose identities (or pseudonymous identifiers) of users whose phones were present in a given area at a given time for the purpose of determining potential crime suspects, witnesses, and victims.
By "geofence" search, I mean the equivalent practice as described above, except as applied to third-party cell phone app providers, such as Google, Facebook, and Apple.

Please provide the following records related to these investigative techniques:

- Policy directives, guidance documents, memoranda, and training materials on requesting (whether by warrant, court order, or otherwise), processing, analyzing, and using tower dump and geofence evidence for investigation and/or court. This request also includes materials that describe the application, function, and use of cell tower dumps and geofence searches including emails, handouts, usage policies, PowerPoint presentations, specification documents, or standard operating procedures.
- Records detailing use of "CAST", "CASTViz", or other cell location data analysis tools the agency may use. Please provide the same for geofence data analysis tools the agency may use.
- Data retention guidelines or policies, data security policies, data security specifications, privacy impact assessments, security audits, or other materials evaluating or guiding the security of cell tower dumps and geofence searches or the privacy of the data involved.
- Contracts or agreements with cell phone service providers (for example, Verizon, AT&T, and T-Mobile) for acquiring data, whether specifically for tower dumps or other purposes (for example, cell phone call records or historical/real-time tracking)
- Contracts or agreements with cell phone app data holders, such as Google, Facebook, and Apple.
- Contracts or agreements with cell phone data analysis providers and cell phone data analysis software vendors (for example, "CellHawk" and "Cellebrite").
- Records relating to the funding for above contracts or agreements.

This includes any correspondence between any staff at this agency with any other organization or vendor relevant to the use of the aforementioned technology or program, including records related to meetings or follow-up actions with any vendors, companies, or other private entities marketing this technology for immigration, intelligence, law enforcement, or any use.

The requested documents will be made available to the general public, and this request is not being made for commercial purposes.

In the event that there are fees, I would be grateful if you would inform me of the total charges in advance of fulfilling my request. I would prefer the request filled electronically, by e-mail attachment if available or CD-ROM if not.

Thank you in advance for your anticipated cooperation in this matter. I look forward to receiving your response to this request within 10 calendar days, as the statute requires.

Sincerely,

Philip Glaser

On January 11, 2024, I requested information related to "tower dumps" and "geofence" searches from the US Attorney for the District of Maryland. On March 5, 2024, the USAO rejected this request as being a state or local exclusive matter. I see that the rejection was lumped in with other requests that do in fact request records for state matters. That is not the case with my request, so its rejection was erroneous.

This request is for records pertaining to the investigatory methods of cell tower dumps and geofence searches. These two methods have been used in prosecutions in US District Courts of the Fourth Circuit (see, e.g., United States v. Walker, No. 2:18-CR-37-FL-1, 2020 WL 4065980 (E.D.N.C. July 20, 2020); United States v. Chatrie, 590 F. Supp. 3d 901 (E.D. Va. 2022)) and I have learned that applications for warrants authorizing such searches have been made in the US District Court for the District of Maryland. The request seeks records pertaining to the training, documentation, and policies for such searches by the US Attorney for the District of Maryland, as entirely distinct from such searches by state and local agencies.