As explained in my preceding post, there appears to be no good rationale for the Justice Department’s decision to grant Cheryl Mills immunity from prosecution for any incriminating data on her computer in exchange for her agreement to surrender the computer. The Justice Department could simply have issued a grand jury subpoena requiring Mills to hand over the computer. Nevertheless, this being a legal discussion, I wouldn’t disappoint you by saying there are no caveats.
I should thus address what’s known as “act of production” privilege. It is derived from the Fifth Amendment privilege against self-incrimination, reflecting the salient difference between (a) a physical object, and (b) the potentially incriminating testimonial implications of surrendering that object to investigators.
The easiest way to think about this is to consider the difference between arrest and interrogation. If, as an investigator, I arrest you for armed bank robbery, I am entitled to get any evidentiary benefit your physical person gives my case. For example, I can put you in a line-up to enable eyewitnesses to identify you as the robber, or I can search your pockets for the money and the gun. But the Constitution bars me from coercing you to make any statements that would help me prove your guilt. Under the Fifth Amendment, you have the right to remain silent.
These same principles operate with respect to physical evidence that is in your possession, even if it is not located on your physical person.
There are some situations in which complying with a subpoena can be the functional equivalent of admitting guilt. Let’s say I’m a prosecutor in a drug investigation. I issue a subpoena demanding that X produce any ledger of illegal narcotics transactions in X’s possession. Turns out that X does possess such a document, but his lawyer realizes that, if X hands the document over to me, this would be an implicit confession that (a) the document is, in fact, a ledger of illegal drug deals, and (b) X has been in possession of it. So, if X were to comply with the subpoena, which the law requires him to do, I would obtain not only the physical ledger, the contents of which I can use in a drug conspiracy prosecution against X; I would also get a windfall: what amounts to testimonial admissions by X that would help me prove his knowing participation in the drug conspiracy.
Obviously, X does not want to give me the ledger. Yet, X knows that he has been issued a lawful subpoena for this physical evidence. If I later find out that he has withheld the ledger in defiance of the subpoena, I could prosecute him for obstruction of justice and contempt.
To resolve this dilemma between (a) the lawful duty to comply with a subpoena demanding production of physical evidence and (b) the constitutional privilege against admitting guilt, the prosecutor grants a limited form of protection known as “act of production” immunity.
Under this arrangement, X must surrender the ledger, and if there is information in the ledger that incriminates X, the prosecution may use that information against X. But the prosecution forfeits the ability to use against X the fact that X, by surrendering the ledger, effectively admitted both that it was a drug ledger and was in X’s possession.
As you can imagine, this is very routine in law enforcement.