How did journalists process and analyze ICE's detentions table to map Alligator Alcatraz transfers?

Executive summary (2–3 sentences)

Journalists reconstructed transfers into and out of “Alligator Alcatraz” by obtaining ICE’s machine-readable detention records and isolating entries tied to the Everglades facility from a massive detentions table, then using the table’s sequential book‑in/book‑out entries to trace movements between facilities and flag gaps where federal locator systems showed no record; NBC6 reported separating Alligator Alcatraz details from more than 917,000 records in that ICE detentions table ^[1]. Reporters cross‑checked those reconstructed transfer chains against ICE’s online locator and attorneys’ accounts, exposing major discrepancies and prompting scrutiny from watchdogs and rights groups ^{[2] [3] [4]}.

1. How the data arrived: FOIA, a giant detentions table, and what it contained

The dataset at the center of the reporting was produced by ICE in response to public records litigation and published as a detentions table that logs every book‑in and book‑out nationwide between October 1, 2024 and October 15, 2025 — a file NBC6 said totaled more than 917,000 records and reflected bookings involving roughly 326,000 individuals because many were booked into multiple facilities during transfers ^[1].

2. Isolating “Alligator Alcatraz” from the national churn

Reporters “separated” the Everglades facility’s records out of that national file to create a sub‑dataset focused on people held at the site, enabling counts (more than 6,700 men recorded at the Everglades center since opening, per NBC6 analysis) and comparisons against public statements by officials about detainee status ^[1]. That same tabular logic — identifying rows with the facility’s identifier and ordering events by timestamp — is what allowed journalists to see chains of book‑ins and book‑outs that indicate transfers rather than single stays ^[1].

3. Reconstructing transfers: reading book‑in/book‑out as movement

Because the detentions table records discrete booking events, reporters used the sequence of entries — e.g., an out‑booking from one site followed by an in‑booking at another — to map transfer routes and durations; NBC6 noted that many bookings show individuals moving among sites, which explains why the 917,000 records represent far fewer unique people ^[1]. Journalists treated repeated bookings for the same unique identifier as evidence of transfers, producing transfer tallies and timelines that revealed rapid movements and, in many cases, short windows that complicated attorney access ^{[1] [2]}.

4. Cross‑checks against ICE’s locator and first‑hand reporting uncovered holes

Having reconstructed transfer trails from ICE’s internal table, reporters compared their maps to ICE’s public detainee‑locator and to attorneys’ and families’ accounts; those comparisons exposed hundreds who no longer appeared in the online system or whose location fields were blank or only advised users to “Call ICE for details,” a discrepancy the Miami Herald documented ^[2]. Independent reporters and outlets likewise documented hundreds of detainees who “dropped off the grid,” findings echoed by Democracy Now! and investigated by others, prompting questions about state‑run processing and federal tracking ^{[3] [2]}.

5. What the data analysis proved — and what it did not

The aggregated records allowed journalists to show concrete patterns: high rates of re‑booking consistent with transfers, a substantial number of men held at the Everglades site who lacked final removal orders contrary to gubernatorial claims, and wide mismatches between internal booking logs and the public locator ^{[1] [2]}. However, reporting teams and watchdogs note limits in the public record: while the detentions table lets journalists infer transfers from sequential booking events, publicly available accounts do not disclose every procedural detail or ICE’s internal reasons for certain gaps, and sources warn that absence from an online locator can reflect multiple explanations that require further agency confirmation ^{[1] [4] [3]}.

6. Wider context and implications drawn from cross‑reporting

The data‑driven transfer maps fed broader reporting and advocacy: Amnesty International and other investigators cited the opaque transfer patterns and apparent absence of federal tracking at the state‑run Everglades site as supporting their conclusions about restricted legal access and enforced disappearances, while outlets and fact‑checkers emphasized that many missing entries reflected transfers rather than necessarily secret deportations — a contested interpretation that remains central to how the public and courts evaluate the facility ^{[5] [3] [4]}.

Limitations: the public reporting specifies the dataset and high‑level methods (separating facility records, sequencing book‑in/book‑out events, cross‑checking against locator tools), but does not publish the full code, matching rules, or adjudications reporters used to resolve ambiguous cases, leaving some methodological detail unverified in the sources reviewed ^[1].