This article first appeared on the Just Security site.

Alex Whiting has already written an excellent clarifying post on Wednesday mornings news that the FBI had conducted an early morning raid of former Trump campaign chair Paul Manaforts home late last month.

But the story is extraordinary enough that I thought it worth a brief follow up, even at the risk of some duplication.

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The first and most obvious thing to note is that having obtained a search warrant entails that Robert Muellers inquiry has turned up at least some concrete evidence of specific criminal conductenough, at any rate, to persuade a judge that there was probable cause to believe a search of Manaforts home would uncover evidence of a particular crime or crimes.

That makes it much more difficult to claim that the inquiry is nothing but a witch hunt, as Donald Trump likes to say, a boondoggle thats stretched on for months without turning up any evidence of wrongful conduct.

Probable cause, of course, is still a far cry from proof beyond reasonable doubt, but theres evidently at least some sort of there there.

Paul Manafort, former chairman of Trump's campaign, at the Mayflower Hotel April 27, 2016 in Washington, DC. Chip Somodevilla/Getty

The more common approach of issuing Manafort a subpoena, by contrast, wouldnt necessarily imply much beyond official curiosity, requiring only that the documents sought have some relevance to a legitimate inquiry.

(For a variety of reasons it seems very unlikely this search was conducted pursuant to a FISA warrant, but in the case of a U.S. person like Manafort, that too would require a probable cause showing of potentially criminal conduct.)

Moreover, realpolitik considerations make it likely that this warrant application would have received particularly exacting scrutiny.

It is not hard to find horror stories about drug raids gone wrong because some magistrate rubber stamped an application based on a dodgy tip and ended up sending a SWAT team into some terrified grandmothers bedroom in the middle of the night.

But everyone involved in this case is well aware that theyre working the highest-profile investigation on the planet, targeting a seasoned political operator with plenty of cash to throw at white-shoe law firms and the president of the United States on speed dial.

Flubbing this would be professionally damaging for all concerned, undermine confidence in the broader inquiry, and perhaps even provide Trump the pretext he so clearly desires for cashiering the special counsel.

It is difficult to imagine the necessary parties signing off on this if the evidence were not compellinglikely more so than would be demanded for a less media-saturated investigation.

The timing also merits comment: By default, warrants are supposed to be executed during ordinary daytime hours unless theres a showing of good cause that an exception must be made, normally either from safety considerations or to prevent the destruction of evidence.

(Here, again, judges are often laxer about authorizing no-knock warrants than I would like, but the same considerations above make a rubber stamp seem less likely in this instance.)

Since we can probably safely rule out fears that Manafort might attempt to reenact the ending of Scarface, it seems reasonable to infer that the good cause in this case concerned the potential for destruction of evidencepresumably some kind of digital documentary evidence that might be very rapidly erased or damaged beyond recovery.

(One aspect Ill admit doesnt quite compute: If you think theres incriminating data Manafort would be prepared to destroy at the sight of an FBI badge through the peephole, wouldnt you expect him to have done so already? This seems less odd if they were interested in recent or ongoing conduct as well as historical records, though probably there are alternative explanations Im not thinking of.)

At this point I should probably stress how unusual this is.

It is always, of course, the case that the target of an investigation has some incentive to suppress or destroy potentially incriminating documents, yet the normal procedure here would nevertheless be to issue a subpoena, not execute a residential searchlet alone a search timed to catch the target asleep.

Some of the reporting about the raid has speculated that this far more intrusive approach was chosen as means of intimidationa way of sending a messagebut, again, the near certainty that the investigators will have to defend their decisions under extraordinary scrutiny would seem to caution against employing such abusive tactics, at least in the absence of some additional, more publicly palatable, rationale.

An alternative hypothesis, then, would be that investigators encountered specific evidence that Manafort had not been, as his attorneys invariably say, giving his full cooperation. (One does not, as a rule, conduct predawn raids of persons one believes to be cooperating fully.)

The search, after all, occurred at a point when Muellers investigation had already been underway for some time. News that the team was probing Manaforts potential involvement in money laundering had surfaced a week prior, but that was hardly the first time the possibility had been broached, and Manafort had already been named as a focus of the FBIs investigation long before Muellers team took over.

Which is to say, the resort to a physical search was almost certainly not a first step, but rather a choice made well into the investigation. Such a drastic move might seem justified if, for instance, documents provided by Manafort did not seem to square with what investigators had obtained from other sources, such as financial institutions.

Whatever the details, the right question to ask is probably not Why did Mueller obtain a warrant rather than just issuing a subpoena? so much as What changed what new information came to lightthat motivated them to switch their approach?

Public reports thus far suggest that the search was primarily focused on obtaining financial and tax records. Thats in line with what Ive expected all along : Collusion is media shorthand, not a defined criminal offense, and in any event fiendishly hard to prove unless your conspirators are boneheaded enough to create a permanent record of themselves colluding in explicit terms.

When two people have a conversation in person, the only available evidence of what they said is normally the recollection of the parties. Large amounts of money, by contrast, are hard to move around without leaving a paper trail.

As many have pointed out, building a financial crimes case against Manafort could be meant as a lever to induce greater cooperation, but it would also be relevant to the broader aim of untangling Russias influence on the presidential election: not only as evidence of a willingness to flout the law, but also as a potential form of Russian leverage over Manafort and, by extension, the campaign.

Finally, an interesting though possibly coincidental tidbit: A few hours after the raid on Manaforts home, Trump launched into one of his trademark Twitter sprees, most notably shocking the Pentagon by announcing a ban on military service by transgendered persons, but also delivering an apparently unprompted attack on (then) Acting FBI Director Andrew McCabe.

Perhaps it wasnt quite as out-of-the-blue as it seemed at the time.

Julian Sanchez is a senior fellow at the Cato Institute and contributing editor for Reason magazine.

More:

What the Raid on Manafort's Home Tells Us About Progress in the Russia Investigation - Newsweek