On Monday, FBI agents executed a search warrant on the Manhattan office of Donald Trump’s longtime attorney, Michael Cohen. The man known as Trump’s personal “fixer” has assumed particular prominence lately because of his role in arranging a pre-election $130,000 payment to adult film performer Stormy Daniels designed to keep her quiet about an alleged affair with Trump.

Trump immediately labeled the raid a “disgrace” and a “witch hunt.” We don’t know precisely what the FBI was looking for and what it might have found. What is clear is that federal searches of lawyers’ offices are extremely unusual and, under Justice Department rules, require extraordinary justification and multiple layers of internal approvals. And then the warrant application must be approved by a federal judge.

Moreover, the Cohen warrant was reportedly sought not by special counsel Robert Mueller’s office but by the office of the U.S. Attorney’s Office for the Southern District of New York, acting on a referral from Mueller. It has been reported that U.S. Attorney Geoffrey Berman (a Trump appointee) recused himself from the Cohen investigation, but the warrant would still have to have been approved by a senior career supervisor in his office. In short, before the application even reached the judge who signed it, it garnered the approval of Mueller and a senior career prosecutor in the Southern District of New York. Moreover, DOJ procedures for approving such a warrant would require the concurrence of Acting Assistant Attorney General for the Criminal Division John Cronan. And the New York Times reported on Tuesday that Deputy Attorney General Rod Rosenstein approved the raid. Any suggestion that this search was a frivolous fishing expedition by an uncontrolled special counsel—or, in the president’s tirelessly repeated phrase, “a witch hunt”—simply won’t wash.

Trump’s statement on Tuesday that “Attorney–client privilege is dead!” is similarly nonsensical. The Department of Justice is acutely conscious that communications between attorneys and their clients enjoy special status under the Sixth Amendment and the common law attorney-client privilege. Except in rare circumstances, attorney-client communications may not be seized for use in investigations or introduced in court to prove a crime. There are exceptions, such as when an attorney gives a client advice about how to commit a future crime, but judges are exceptionally protective of the attorney-client relationship and tend to construe such exceptions very narrowly.

Judges review an application to search a lawyer’s office with infinitely more care than a warrant for virtually any other location.

Therefore, any law enforcement search of an attorney’s office will always be a ticklish business. Even when a search is authorized by warrant, merely locating the material covered by the warrant will almost inevitably involve inspecting documents that contain attorney-client communications for clients other than the one who may be the subject of the warrant. And once the batch of material related to the client at issue is found, there are very likely to be some communications covered by the privilege commingled with material that has no attorney-client communications or communications that are unprivileged.

The likelihood of encountering commingled privileged and unprivileged material creates a special problem—if the searching agents see privileged matter and accidentally or purposely convey such material to the agents and prosecutors who ultimately charge and prosecute the case, the privileged matter may “taint” the rest of the evidence and could require suppression of some evidence or even dismissal of the entire prosecution.

For all these reasons and more, the Justice Department has special detailed procedures for authorizing and conducting attorney searches. Before a warrant can even be presented to a federal judge for approval, the following internal steps must be taken:

1. The prosecutor contemplating an attorney warrant must consider whether the material sought can be obtained by any less intrusive means, such as a subpoena. U.S. Attorneys Manual 9-13.420(A).

2. Any attorney search warrant must be approved by the U.S. attorney in the district where the warrant is sought. U.S.

Attorneys Manual 9-13.420(B).

3. A prosecutor seeking an attorney warrant for material concerning representation of a client must also obtain prior approval of the assistant attorney general in charge of the Criminal Division in Washington, using a specific and highly detailed application form. U.S. Attorneys Manual 9-13.420(C).

4. Because of the risk of taint, DOJ rules require that an attorney warrant application specify procedures for guarding against it. DOJ rules state: “Procedures should be designed to ensure that privileged materials are not improperly viewed, seized or retained during the course of the search. … [I]n all cases a prosecutor must employ adequate precautions to ensure that the materials are reviewed for privilege claims and that any privileged documents are returned to the attorney from whom they were seized.” U.S.

Attorneys Manual 9-13.420(D).

5. Those anti-taint procedures will customarily involve a separate team of agents and lawyers charged with executing the search and reviewing the materials found in order to limit the material seized to matters that (a) are covered by the warrant, and (b) are not privileged. Those agents and lawyers will be strictly barred from communicating to the main prosecutorial team any documents or information deemed privileged or outside the scope of the warrant.

Often, the final privilege determination will be made by submitting material about which there is question to a judge or special master.

The procedural and logistical difficulties in seeking and executing a warrant for an attorney’s office have the practical effect of making such searches extraordinarily rare. When permission to seek judicial approval of such a warrant is sought, you can be assured that the highest levels of the Justice Department have been satisfied on two critical points: First, the information sought is of very high importance to a case of genuine significance, and second, the evidence supporting issuance of the warrant is very solid.

Moreover, a judge may not authorize any warrant without finding probable cause that a crime has been committed and that evidence of the crime will be found at the place to be searched. And judges review an application to search a lawyer’s office with infinitely more care than a warrant for virtually any other location.

These general observations would likely be triply valid in the case of the president’s personal lawyer.

We can’t yet know what the FBI was searching for or what they found. But we can be absolutely sure the Department of Justice had darn good reasons to look for it.