The editor-in-chief at a well-known legal news website argued in an opinion piece on Tuesday that special counsel Robert Mueller’s team might have violated former Trump campaign chairman Paul Manafort’s Fourth Amendment rights, which could lead to major problems for the special counsel.

Mueller’s team raided Manafort’s multimillion-dollar home in Alexandria, Virginia on July 26, 2017, and in the process of executing a search warrant, they might have violated the law with some of the material they recovered, Rachel Stockman wrote at Law Newz.

According to CNN, Mueller’s team took documents during the raid that they were not allowed take:

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.

Stockman wrote that Manafort’s attorneys will seize upon this misstep by Mueller’s team and that the situation raises serious issues surrounding Manafort’s constitutional rights, which could throw the investigation off balance as investigators cannot “unsee” evidence once they have seen it.

Stockman cited a 2005 article from Eric D. McArthur — Deputy Associate Attorney General at the U.S. Department of Justice (DOJ) — in which McArthur states the potential consequences that can stem from investigators violating the attorney-client privilege:

[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.

In a fraud case involving a Wall Street financier earlier this year, a federal judge dismissed all evidence collected by prosecutors because they violated the defendant’s Fourth Amendment rights. Reuters reports:

U.S. District Judge Alison Nathan said “blanket suppression” was necessary because “sweeping” January 2012 searches of Wey’s Manhattan apartment and the offices of his consulting firm, New York Global Group, violated his Fourth Amendment constitutional right against illegal searches and seizures.

In a 92-page decision on Tuesday night, the Manhattan judge said prosecutors failed to show they needed broad warrants because they had probable cause to believe Wey’s entire business was a scam.

Items seized included children’s school records, divorce records, family photos, medical records, prescription documents, recreational schedules, resumes and X-rays, the judge said.

“This conduct reflects, at least, grossly negligent or reckless disregard of the strictures of the Fourth Amendment,” Nathan wrote.

Former federal prosecutor Henry Hockeimer told Law Newz that the actions by Mueller’s team could spell serious trouble for their investigation into Manafort.

“If they [investigators] had any kind of heads up, and they went beyond the scope of the warrant, that could be a problem,” Hockeimer said. “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.”