OPINION | Why did the FBI raid Paul Manafort’s home?
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News that FBI agents executed a "raid" in the wee hours of the morning of July 26 at the home of former Trump campaign chairman Paul Manafort created a new wave of buzz, speculation and debate.

There is no doubt that the move is very significant: It means that special counsel Robert Mueller has concluded that there is good reason to believe that a crime has been committed and that evidence of that crime would be found at Manafort's home. 

But it goes without saying that the FBI cannot search anyone's home without permission. So when you hear a news story about a "raid," that means the FBI sought and obtained a search warrant. To obtain a search warrant, a federal prosecutor works with an FBI agent to write an affidavit in which the agent explains under oath the evidence supporting that search warrant. 


In the affidavit, the agent has to set forth evidence to establish "probable cause" that a crime has been committed. That basically means that the agent has to show that there is good reason to believe a crime was committed. A search warrant asks to search for particular things in a specific place, so in the affidavit the agent has to explain why those things would be evidence of the crime and why there is good reason to believe that they'll be found in that place.


In the case of Manafort's home, the FBI agent would need to set forth the evidence they were looking for, such as specific documents and records. If the records weren't the sort of thing that people usually kept at home, the agent would need to explain why they believe Manafort kept those records at his home. Then the prosecutor on Mueller's team would present that affidavit to a federal judge as part of an application for a search warrant.

That brings us to the most important implication of the news of the Manafort raid. The fact that a search warrant was issued means that a federal judge also concluded that there was good reason to believe that a crime was committed and that evidence of that crime would be found at Manafort's home. As far as we know, that is the first time that an independent third party concluded that there was evidence of criminal activity involving anyone related to Mueller's investigation.

The fact that Mueller chose to obtain a search warrant of Manafort's home was unusual, because typically documents are obtained by issuing a subpoena to a person's attorney. To issue a subpoena, a prosecutor doesn't have to write a long affidavit and agents don't need to wake up early to go to a home and collect evidence. Issuing a subpoena puts all of the work on the person's attorney to collect the documents, weed out what's irrelevant and organize the documents into a format that the prosecutor can use.

So if issuing a subpoena is so easy and cost-effective, why obtain a search warrant in this context? The obvious implication is that Mueller believed that if he issued a subpoena, he would not receive all of the evidence that the agents would collect if they searched his home. Why not? Perhaps they were concerned that evidence was being altered or destroyed, or that Manafort's attorneys were asserting the Fifth Amendment and withholding the production of documents because the act of producing them would itself incriminate him. Maybe they were just being extra cautious given the importance of the investigation. 

One thing we can be sure about is that at the time this warrant was issued last month, Manafort had not "flipped" and provided evidence implicating others. Prosecutors don't obtain search warrants for the homes of "flippers" because cooperators are doing everything within their power to help the government, and would consent to a search if asked. 

Once agents entered Manafort's home, they could search and seize specific items that were outlined in the search warrant. If they saw contraband like narcotics or child pornography during their search they could seize that. But if they merely saw documents that could provide evidence of another crime, they may need to go back to the judge for permission to seize those documents, depending on the scope of the original warrant. Agents also would need a separate search warrant to search a safe or a computer.

One question I was asked many times on Twitter since this news broke is why people who are under investigation don't destroy all of the evidence before law enforcement comes. The simple answer is that the downside of being caught destroying evidence is very high. I always make sure my clients know that destroying evidence can be a separate crime and is evidence of your guilt as to the crime under investigation. Deleting files can also leave behind digital fingerprints and there can be duplicate files elsewhere.

We won't know for sure what evidence Mueller used to obtain the search warrant for quite some time, because the search warrant is almost certainly under seal.

But before leaving the residence, agents typically leave behind a copy of the search warrant, which details the items that they were authorized to seize. If that document gets into the hands of the press, we can learn what crime Mueller is investigating and get a sense of what evidence the FBI was looking for. Until then, we can only wait for the next shoe to drop in this investigation. 

Renato Mariotti is a former federal prosecutor in the Securities and Commodities Fraud Section of the United States Attorney's Office in Chicago and he has prosecuted federal obstruction of justice cases. Follow him on Twitter @renato_mariotti.

 The views expressed by contributors are their own and are not the views of The Hill.