manafort
© Matt Rourke/Associated Press/FileFormer Trump campaign chairman Paul Manafort is sure to be indicted as a result of the Mueller investigation, sources say.
Ex-campaign adviser Paul Manafort turned himself in Monday after being indicted for money laundering, and a slew of other financial crimes. The feds alleged he illegally funneled millions of dollars of payments into offshore bank accounts in order to avoid detection by U.S. authorities as it related to his work on behalf of former Ukrainian President Viktor Yanukovych. While the indictment containing Manfort's alleged criminal activities is very detailed, and well-documented, there is one area that could hurt Mueller's investigation. Mueller's team may have obtained evidence in the raid of Paul Manafort's home that was not covered by the search warrant. That could be problematic.

In a surprise raid on July 26th, FBI agents busted into Manafort's home in Alexandria, Virginia to collect documents and other materials related to the FBI probe into whether the Trump campaign colluded with the Russians. At the time, Manafort's attorney raised concerns about how the raid was conducted. In order for the feds to obtain a warrant, a federal judge would have to determine that probable cause existed that a crime was committed. As part of the warrant, investigators attached an affidavit which contained a list of items that FBI agents hoped to collect. That's where the trouble appears to be in Manafort's case.

As a legal website, we were immediately drawn to the revelation that evidence was collected that may not have been covered by the warrant. That's a serious development, and one that Manafort's attorneys will no doubt seize upon. But, is it necessarily illegal? Did the agents do anything wrong? It's not clear. It certainly could raise some serious constitutional issues that could taint the investigation.

Through an older CNN article, we get a bit more of a hint about what specifically the agents may have gathered:
During that raid, Mueller's investigators took documents considered to be covered by attorney-client privilege, sources told CNN. Lawyers from the WilmerHale law firm, representing Manafort at the time, warned Mueller's office that their search warrant didn't allow access to attorney materials. The documents in question have now been returned, the sources say.
As the article points out, this certainly brings up concerns as to what exactly was seized, what investigators saw, and who handled the material. You can't "unsee" evidence once you saw it.

"If they (investigators) had any kind of heads up, and they went beyond the scope of the warrant, that could be a problem," Henry Hockeimer, a former federal prosecutor, told LawNewz.com.

In 2005, Eric D. McArthur, who coincidentally now serves as Deputy Associate Attorney General at the U.S. Department of Justice, authored an article about the Fourth Amendment implications if investigators collect attorney-client privileged information. He wrote:
[T]he Fourth Amendment is violated when the government purposely, knowingly, recklessly, or negligently searches privileged attorney-client communications. In other words, the Fourth Amendment is violated whenever law enforcement officials have reason to believe that a search or seizure is likely to expose them to privileged attorney-client communications and fail to take reasonable steps to minimize their exposure.
A similar issue came up recently in a case against Wall Street financier Benjamin Wey. A federal judge threw out all of the evidence gathered against him through warrants because the "sweeping" searches of his property violated his Fourth Amendment right. Judge Alison Nathan found that the searches were "grossly negligent" in that they collected evidence that went beyond the scope of the warrant like medical records, and divorce records. In the case of Manafort, it appears that his lawyers warned investigators about the existence of attorney-client privileged documents and memos. If investigators didn't take the proper precautions to avoid collecting these documents, they could be in trouble for violating Manafort's constitutional rights.

If, on the other hand, investigators accidentally seized privileged attorney-client communication, they could be in the clear, as the Supreme Court has found this is probably not a Fourth Amendment violation. In other words, if agents just made an innocent mistake, quickly returned the documents, they may be okay, depending on the steps that were taken. It is not clear at this point when Manafort's lawyers warned the FBI of the existence of this material.

"Generally, if agents seize privileged materials, (Manafort) could argue the entire search was tainted, they went beyond the scope of the warrant. A defense attorney could make some hay out of this," Hockeimer said.