That's because Cohen's potential testimony could expose sensitive information related to Trump, like his tax returns or information about his personal finances.
The FBI raid on Michael Cohen's office and hotel room on Monday raises new questions about the disposition of Cohen and his longtime client, President Donald Trump.
During the surprise raid, federal agents seized "privileged communications" between Cohen and his clients, Cohen's lawyer, Stephen Ryan, said in a statement. Some of those client communications could include work that Cohen has done for Trump.
Cohen is reportedly the subject of an investigation into bank fraud and campaign-finance violations. He's been under increased scrutiny ever since he revealed he personally executed a $130,000 payment to the porn star Stormy Daniels, the woman who says she had a sexual encounter with Trump. Cohen made that payment 11 days before the 2016 US election.
Cohen has said that he paid the money out of his own pocket, and that Trump had nothing to do with the agreement. Trump echoed the same last week, in his first public comments about the arrangement.
That $130,000 wire-transfer to Daniels, whose real name is Stephanie Clifford, raised alarms on multiple fronts:
All told, the facts of the case that prosecutors appear to be building around Cohen's work and those "privileged communications" between Cohen and his clients could, in theory, prompt those prosecutors to call Cohen to testify against his own clients. That may include Trump, potentially opening the vault to sensitive information about his personal finances.
According to the American Bar Association (ABA), specific legal boundaries have to be breached in order for the attorney-client privilege to be rendered void and force the attorney to testify against the client in a criminal case. It's called the "crime-fraud exception."
The crime-fraud exception can only be triggered if the work product between the attorney and client "was actually used in the furtherance of the purported crime or fraud," the ABA says.
If a client seeks their lawyer's advice on a matter that could be illegal or expose them to criminal liability, and the client uses the advice to commit a crime or act of fraud, the attorney could be asked to testify against their client. The same applies if the attorney is the one accused of committing a crime or fraud as part of their work for the client.
Two conditions must be met before the crime-fraud exception is triggered. According to the ABA, there needs to be a "reasonable basis" to suspect that:
There remains much that is still not publicly known about the case prosecutors are building against Cohen — including whether he or Trump acted criminally or fraudulently as part of their attorney-client relationship with regard to the $130,000 payment to Daniels, or any other matter.
But the developments on Monday make it clear that, as this and the other threads surrounding the multiple investigations into Trump and his associates continues, the boundaries of legal precedent are being tested in ways unlike any other point in modern history.