A federal magistrate judge in Chicago has rejected a request by the government for a provision in a search warrant that would authorize agents to compel people present to unlock seized phones using biometric readers. I think the judge was right to reject the provision, although I disagree with substantial parts of the reasoning.

I. The New Opinion

In the case, an Internet connection (presumably at a home) is being used to traffic in images of child pornography. The government wants the authority to search the place and seize any computers located there. The magistrate judge allows that. The government also wants a provision in the warrant authorizing the police to compel “any individual who is present at the subject premises at the time of the search to provide his fingerprints and/or thumbprints onto the Touch ID sensor of any Apple iPhone, iPad, or other Apple brand device in order to gain access to the contents of any such device.” The magistrate judge rejects that provision, issuing the warrant without it.

The magistrate judge offers two reasons for rejecting the fingerprint provision. First, the opinion suggests that making a person give a fingerprint raises case-by-case questions of reasonableness under the Fourth Amendment that cannot be addressed with a blanket authorization. According to the court, “the warrant does not establish sufficient probable cause to compel any person who happens to be at the subject premises at the time of the search to give his fingerprint to unlock an unspecified Apple electronic device.” Lots of people might be present on the premises at the time of the search, but there is no way to know ahead of time whether there will be sufficient cause to seize each person needed to make then unlock a particular phone.

Second, the judge suggests that obtaining thumbprints will violate the Fifth Amendment because cellphones contain very sensitive information. The common wisdom is that an order to place a particular thumb on a thumbprint reader doesn’t violate the Fifth Amendment because it isn’t testimonial. It doesn’t reveal what is going on in the person’s mind, so it’s not the person’s testimony. But the magistrate judge disagrees:

[T]he connection of the fingerprint to the electronic source that may hold contraband (in this case, suspected child pornography) does “explicitly or implicitly relate a factual assertion or disclose information.” Doe, 670 F.3d at 1342. The connection between the fingerprint and Apple’s biometric security system, shows a connection with the suspected contraband. By using a finger to unlock a phone’s contents, a suspect is producing the contents on the phone. With a touch of a finger, a suspect is testifying that he or she has accessed the phone before, at a minimum, to set up the fingerprint password capabilities, and that he or she currently has some level of control over or relatively significant connection to the phone and its contents.

The government cites United States v. Wade, for the proposition that the Fifth Amendment privilege against self-incrimination offers no protection against compulsion to submit to fingerprinting. (Gvt. Mem. at2) (citing Wade,388 U.S. 218,223). This case, however, was decided in 1967, prior to the existence of cell phones, and in the context of utilizing fingerprinting solely for identification purposes. In the context of the Fifth Amendment, this Court finds these two starkly different scenarios: using a finger print to place someone at a particular location, or using a fingerprint to access a database of someone’s most private information. The Wade court could not have anticipated the creation of the iPhone nor could it have anticipated that its holding would be applied in such a far-reaching manner.

II. My Analysis — the Fourth Amendment Issues

I think the judge was correct to reject this provision, although not quite for the reasons stated. The proper reason to reject this provision is that warrants cannot and should not regulate how a warrant is to be executed. The warrant has to state where the police can search and what they can seize there. But what else happens when the warrant is executed is a matter of case-by-case reasonableness, and magistrates shouldn’t try to insert themselves into that by imposing blanket reasonableness determination ex ante when they have no idea what the facts will turn out to be.

This principle most often comes up when judges want to impose ex ante restrictions on computer warrants. Those restrictions might be search protocols or restrictions on when seized computers have to be returned. I argued in a 2010 article that these limits are improper. The reasonableness of the search has to be determined ex post, I argued, not answered by a magistrate judge ahead of time when the warrant is issued.

A warrant provision providing authorization to get thumbprints is the mirror image of ex ante restrictions. Now the government wants ex ante approval of steps in the execution of the warrant rather than judges wanting ex ante disapproval of steps. But the principle is the same. Just as a magistrate judge can’t gauge at the time of the warrant application what limits on the execution of the search would be proper, neither can a magistrate judge gauge what added government steps would be proper. We have to wait for the execution of the search and for reasonableness determinations to be made on the scene by the officers and then reviewed ex post by courts.

This point is true even if courts in future ex post litigation rule that a particular thumbprinting practice complies with the Fourth Amendment. If courts later issue those rulings, then magistrates still shouldn’t include provisions about them in warrants. Instead, they will become part of background Fourth Amendment principles that apply to every warrant. And notably, the Fourth Amendment cases the court discusses on detention and fingerprinting are all about what was deemed reasonable ex post. None of them are about provisions included in a warrant ex ante.

If I’m right that this fingerprint provision is categorically improper, one question is why is the government seeking it. What’s the perceived advantage? I suspect there are two reasons. First, prosecutors and agents are probably thinking that magistrate preapproval will help trigger the good-faith exception of United States v. Leon. If a particular fingerprinting is later questioned in court, and a judge rules that it was improper, agents can fall back on the “preapproval” of the process in the warrant to avoid suppression. If that’s what they are thinking, it’s all the more reason to reject the provision: It makes no sense for magistrate “preapproval” of something they have no authority to “preapprove” to change whether the exclusionary rule applies.

Second, prosecutors and agents may be thinking that including the provision in the warrant will encourage people not to resist giving their thumbprints. Agents won’t want to force people to put their thumbs on the phones; they would rather those present do so without force. With a warrant in hand saying that a judge has ordered it already, people are probably more likely to submit. But if that’s the concern, I think the same objective could be met with an appellate court ruling saying that the thumbprints are permitted as a matter of Fourth Amendment law. Agents could show people a summary of the law on the issue, printed up on government letterhead, and I think that would have equivalent persuasive force. And of course that assumes that the courts would issue such a blanket ruling. Whether that is true would have to be litigated first, obviously.

I interpret the judge’s Fourth Amendment analysis to be at least somewhat in sync with the argument I have made here. On that basis I think the judge was correct to reject the provision, although I would have expressed the Fourth Amendment argument somewhat differently.

II. My Analysis — the Fifth Amendment Issues

On to the Fifth Amendment issues. I wrote a long blog post last year on why I think compelling fingerprints to unlock phones can but usually won’t raise Fifth Amendment issues: “The Fifth Amendment and Touch ID.” That post largely explains why I disagree with much of the magistrate judge’s Fifth Amendment analysis. The judge seems to think that using a person’s body to reveal really private information somehow makes it testimonial; it is using the body to produce evidence, after all. But the Fifth Amendment is solely concerned with compelling use of the mind, not compelling use of the body.

There are ways that compelling someone to place fingers on biometric readers can require use of the mind, as I argued back in October. Imagine the police walk up to a person present at the scene and say this: “Here are 10 phones, and you have to pick out your phone and unlock it with Touch ID.” Complying will be testimonial as to which phone belongs to that person and will amount to testimony that they know which part of their body unlocks it. On the other hand, if the police walk up to a suspect and say, “place your right thumb on this phone,” complying won’t amount to testimony about anything.

The fact that iPhones didn’t exist in 1967 is irrelevant, as is the fact that the police are ultimately able to get lots of personal information by unlocking a phone. Those are relevant to the Fourth Amendment analysis, as the Riley case shows. But they’re not relevant to the Fifth Amendment standard.

I’ll conclude with a procedural point. I’m skeptical that possible Fifth Amendment issues that might arise in the execution of the warrant are properly before the court. For the Fifth Amendment to apply, the person must first expressly invoke the privilege. Given that people may or may not invoke their Fifth Amendment rights, I’m skeptical that there is a ripe dispute now that can allow a court to adjudicate the Fifth Amendment issue. This concern would be solved by removing the provision from the warrant, as I think the Fourth Amendment requires.