Osler's Razor

When I was a prosecutor, one of the tools we had access to (even back then) was a remarkable financial database at the Treasury Department: the Financial Crimes Enforcement Network, or FINCEN.  Among the documents available at FINCEN were "Suspicious Activity Reports," which banks were required to file when transactions raised certain red flags. Because much of the most serious systemic crime-- from drug trafficking to terrorism-- runs on a flow of money, these are very useful.

In a recent report in the New Yorker,  recent Pulitzer-winner Ronan Farrow reveals something that will in the end be a big deal in the Mueller investigation (if it is true). Apparently, two SARS reports relating to large transactions by Michael Cohen were removed from the FINCEN database. Which... well, that just does not happen at random. Certainly, Mueller could have gotten the same information from other sources (particularly within Cohen's own records or those of the bank), but the removal on its own could be a suspect action.

Who removed them?

That is the question Mueller will want answered (provided that he or the US Attorney for the SDNY did not remove them, which seems a small possibility). And it will be discovered. If the culprit is a political actor trying to remove the documents from view because of their damaging nature to the President, he or she will be prosecuted. This is the clearest example of obstruction of justice one can imagine, short of shooting a witness.

For a prosecutor, this is a big deal, and the prosecutors will be extremely motivated. They care so much because this crime, in particular, strikes at the integrity of the very tools they are supposed to rely on. Don't mess with a worker's tools-- there will be hell to pay.