Interpreting, accurately, what isn’t there — the Redactor’s Dilemma

Any lawyer knows that “non-facts” — what people don’t do, things that don’t happen, words that aren’t said — are as telling as what we typically think of as “facts.” Julian Sanchez, in a post entitled The Redactor’s Dilemma, gives a brilliant demonstration of this truth. Sanchez has been “poring over the FOIA documents on cell phone lojacking obtained by the ACLU.” Like many stacks of documents lawyers are accustomed to examining, the ones Sanchez examined are heavily redacted. As he explains:

[O]ver time, you start developing little heuristics for trying to put the puzzle pieces together, to at least limit the domain of what might be in those black boxes. What can context tell you? What can you infer from the length of the redacted material? Looking at these sets of documents, I think I may have picked up on an interesting variation on Mike Masnick’s “Streisand Effect”—that now-familiar phenomenon where efforts to suppress information end up drawing all the more attention to it.

It was pretty easy for Sanchez to figure out that one of the redactions was the statutory definition of “basic subscriber information” found in the U.S. Code, and his first reaction was to wonder [w]hat sort of jackass . . . had concluded that the contents of American public laws were some kind of operational secret?” But then, of course, he realized “the investigative technique [the redactors were] taking pains to conceal . . . involved exploiting that part of the statute in some crucial way.” The post is worth reading in its entirety for the truth it uncovers: prosecutors are seeking cell tower information from telcoms, rather than GPS info, because doing so requiring the prosecutors to satisfy a lower legal standard and they can easily get enough from that information to determine where a person is.

But what I find most interesting is what Sanchez calls the Redactor’s Dilemma — the huge risk that redactions themselves will reveal to informed readers what it is that’s been redacted:

Imagine you’re given the task of censoring documents like these for public release. There are some bits that you just obviously cut out—whole paragraphs describing operational details that, for good reasons or bad, you want to keep secret. But that won’t be quite enough. Because you’re probably going to have folks reading the documents who know a little something about the law, a little something about the relevant technology, and a little something about surveillance tactics generally. Folks who might piece together one of those facts you’ve excised, not from an explicit statement, but from individually innocuous clues that would nevertheless reveal something if an attentive reader pus them together in the right way.

This is where the dilemma arises. Because if anyone does happen to determine, by other means, what lies behind one or two of those black boxes, you’ve actually given them a much bigger clue. You’ve pointed them to the precise facts that, assembled in the proper order and with the right background knowledge, hint at what you were trying to hide—facts they might otherwise skimmed over without a second glance. But it’s worse than that, even. Because the facts really are more or less innocuous in isolation, a lot of that information won’t be secret per se. The choice of just which lines to redact involves a fair amount of imaginative guesswork—which bits might a reader combine in a chain of inference? That means if similar documents are being censored by different redactors, you’re apt to get the worst of both worlds—many pieces of the puzzle left exposed in one document or another, sufficiently parallel in structure to make them mutually completing, with the potential significance of each one highlighted by its absence from the others.