On Wednesday news broke that at the end of last month, FBI agents searched one of Paul Manafort’s homes for documents as part of the Russia collusion investigation, directed by special counsel Robert Mueller. What is the significance of this news, and why didn’t Mueller just obtain the documents by grand jury subpoena?

Mueller’s use of a search warrant tells us that he was able to establish on the basis of evidence, and to the satisfaction of a United States Magistrate-Judge, that there was probable cause to believe that evidence of a specific crime or crimes existed in the location to be searched. That standard is significantly higher than what is required to obtain a grand jury subpoena, which can be used to obtain any evidence that a grand jury (under the direction of a prosecutor) decides will be helpful to their investigation. Mueller’s resort to a search warrant shows, therefore, that his investigation has advanced, has identified specific potential crimes, and is zeroing in on key evidence. Since it was Manafort’s house that was searched, it is likely that he is implicated in the crimes, but that is not necessarily the case. Further, it should be clear that just because Mueller has now reached this stage in the investigation, it does not necessarily mean that Manafort or anybody else will be ultimately charged with crimes.

Now why did Mueller use a search warrant instead of a subpoena, particularly since Manafort’s attorney says that they have been cooperating with the investigation all along? I can think of four possible reasons for Mueller’s move (none of which are mutually exclusive).

First, Mueller and his staff may have decided that, despite the claims of cooperation from Manafort’s lawyer, Manafort could not be trusted to provide all of the documents requested by subpoena. If Mueller’s team thought that there was any risk that Manafort would hide or destroy documents, that would be a strong reason to proceed with a search warrant.

Second, there may have been a need to move quickly. If Mueller used a grand jury subpoena, he would have had to give Manafort a reasonable amount of time to comply, and that time might have been further prolonged if Manafort’s lawyer challenged any aspect of the subpoena. Mueller may have needed the documents quickly in order to identify other lines of inquiry or for purposes of witness interviews, and so may have decided that using a search warrant would be more expeditious.

Third, Mueller may have wanted to avoid any Fifth amendment objections to a grand jury subpoena. Although recipients of grand jury subpoenas demanding documents ordinarily cannot resist on self-incrimination grounds, because the documents requested were not themselves “compelled” and therefore do not fall within the privilege, there are narrow situations when witnesses can claim that because the government is engaged in a fishing expedition, compliance with the subpoena requires a testimonial act by the witness which could be self-incriminating (I wrote about this possibility here in detail in connection with Congressional subpoenas to Michael Flynn). While a search warrant does not simply permit a fishing expedition, as the government must describe with some particularity the documents it is seeking, it nonetheless forecloses the Fifth amendment objection that Manafort’s lawyer might have mounted in response to a subpoena.

Finally, Mueller’s move may have been in part strategic. He may have wanted to get Manafort’s attention to emphasize the seriousness and advancing nature of the investigation, all with the hope of securing his cooperation. A predawn search by FBI agents of Manafort’s house could achieve this objective in a way that a grand jury subpoena just couldn’t. And if Mueller was hoping to send a message, it is one that will likely be received by others in addition to Manafort. If it was not clear already, it should now be plain that Mueller will use all the investigative tools at his disposal to fulfill the task that he has been assigned.

Image:  Getty/Drew Angerer