There was an interesting exchange during a Senate Intelligence Committee hearing yesterday concerning the use of the Patriot Act’s §215 orders for business records and other tangible things. FBI Director Robert Mueller hinted that the orders may have been used to track purchases of hydrogen peroxide purchases in the investigation of aspiring bomber Najibullah Zazi, while Sen. Ron Wyden (D-Oreg.) asserted that there is “a huge gap today between how you all are interpreting the PATRIOT Act and what the American people think the PATRIOT Act is all about and it’s going to need to be resolved.”

Let’s leave our curiosity about that by the wayside for the moment, though. I’m curious about one simple empirical claim Mueller made in his testimony: That the provision has been used over 380 times since 2001. I assume he’d know, but that seems inconsistent with what’s been publicly reported to date. It’s worth noting that there are actually minor discrepancies between the numbers provided in Congressional Research Service reports, audits from the Office of the Inspector General, and the Justice Department’s annual reports to Congress. But there are plenty of legitimate reasons these numbers might vary depending on how you count, and the total variance is a difference of about 17 orders total over the years.

We know from those Inspector General reports that the majority of those 215 orders issued were “combination” orders issued in tandem with another type of surveillance order called a “pen register” so that investigators could get subscriber information about the people whose communications patterns they were tracking. When Congress amended the Patriot Act in 2006, it built that authority right into the pen register statute, making it unnecessary to seek those “combination” orders. Prior to the amendment, the government got 173 of those “combination” orders. “Pure” 215 orders, which are now the only type needed, have been used much more sparingly. None were issued at all until 2004, and from 2004 through 2009 (depending on whose tally you want to use) there were between 75 and 92 orders issued (for an average of 12–15 annually since 2004). Throw in the combination orders and the upper-bound number through the end of 2009 is 265 orders.

Unless I’ve miscounted or missed something significant—you can get the reports at the links above and check my math—that leaves 115 orders unaccounted for, assuming Mueller’s number is accurate. There are two possibilities, then: Either the government got ten times as many orders in 2010 as the historical average (the figures should be out sometime in April) or there are a whole lot of these missing from the public reporting. Possibly these have something to do with the “sensitive collection program” in which these orders play a key role, alluded to in a Justice Department official’s testimony at a hearing during the 2009 reauthorization debate. Either alternative seems like it would merit additional scrutiny. I sent an e-mail seeking clarification this morning to some of the experts at the Congressional Research Service responsible for keeping legislators informed on these issues, but haven’t yet heard back.

I’m not belaboring this because it’s inherently hugely significant whether the government has used this authority 265 times or 380. Ideally, in the coming months we’ll see a substantial narrowing of National Security Letter authority, which would predictably lead to a large increase in the number of 215 orders issued. And that would be entirely proper, since it would mean more information being sought pursuant to a judicial order rather than FBI fiat. What I do think is significant, however, is that this reminds us how little we know—and how little the vast majority of legislators know—about the use of these powers. In contrast with criminal investigative tools, these powers are entirely covert: People whose records are swept up by the government almost never learn about it, and the recipients of the orders are subject to an effectively permanent gag on speaking about them. Rulings of the secret FISA Court interpreting the scope of these authorities are never made public. Our assurance that they have been or will continue to be used properly rests entirely on the minimal required reporting to Congress and the findings of internal audits. And yet it’s hard to pin down the facts on even this most elementary factual question about 215 orders: How many times have they been used?

Despite this, we have legislators confident enough that these expanded powers are both so necessary and so well controlled that they’re advocating making them permanent. I wish I were as confident.