Touch ID is a fingerprint authentications installed in the products of Apple Inc. (“Apple”), among which are iPhone 5S and the more recent versions of iPhones. In this system, the user’s fingerprint is used to unlock the devices. Apple states that this fingerprint data is stored locally, not in cloud , which makes forensic investigators very difficult to access externally. Further, the entry of a passcode is required “when more than 48 hours have elapsed from the last time you unlocked your device,” which makes it more complicated for criminal investigation since passcode breaking is much more challenging.

Thus, acquiring fingerprint data has become crucial for the law enforcement when an Apple device is involved in a crime which is locked by Touch ID.

Fingerprint data can be obtained through other government databases such as those of immigration registration. Investigators can also use fingerprints from a dead person because it is said that this does not give rise to the privacy issues or the self-incrimination issues.

When these sources are not available, the investigators have sought search warrants that allow them to enforce persons at the subject premise to depress their fingerprints. It has been conducted since around 2014 , and has become routine especially in California.

However, on Feb. 16, 2017, the US District Court for the Northern District of Illinois Eastern Division blocked the issuance of a search warrant allowing the law enforcement agency to compel individuals to provide fingerprints.

In the case, the government asked the court to issue a warrant “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”.

The court discussed two issues: those on the Fourth and Fifth Amendments. In summary, it stated that there needs to be more specific facts to establish sufficient probable cause under the Fourth Amendment as to “who is involved in the criminal conduct linked to the subject premises” or as to “what particular Apple-branded encrypted device is being employed” Moreover, the court concluded that considering the nature of Apple electronic devices which “potentially contains some of the most intimate details of an individual’s life” and the situation in this case where the law enforcement had no showing that “the location, existence, and authenticity of the purported evidence is known with reasonable particularity,” seeking the forced printing to hand over the information in devices is regarded as compelled self-incrimination forbidden under the Fifth Amendment.

Nonetheless, the court mentioned that the Fourth Amendment does not protect privacy interests of a fingerprint itself. What it was concerned was how the print is collected.

Additionally, regarding the Fifth Amendment, although the court said that if “the location, existence, and authenticity of the purported evidence is known with reasonable particularity” and “the contents of the individual’s mind are not used against him” (so-called “foregone conclusion”)—with this logic, it seems that compelling the depression of fingerprints will always be regarded as forced self-incrimination since the contents of a device is unknown to the agency until it is unlocked--, the court concluded that the warrant can be issued if sufficient evidence and information are submitted.

In overall, even though it refused to order a warrant under the circumstances herein, it has not closed the door to all search warrants that compel an individual to forced fingerprinting.

Hence, under this decision, the government can obtain fingerprint data by a search warrant with a sufficient evidential cause against persons found at the subject premises at the time of searching.

However, what if anyone but an Apple device was found on the search site? Can an investigator ask the court to issue a warrant that compels the owner to depress his fingerprints after its seizure? From the logic of the decision above, one should think that a government cannot go as far as to compel a person to give his fingerprint after the seizure. The court implies that the detention in order to get the fingerprint at the search site is allowed because it represents “only an incremental intrusion on personal liberty when the search…has been authorized by a valid warrant.” And summoning a person to get his fingerprint is surely not an incremental intrusion. Then, the law enforcement might have to use the All Writs Act (“AWA”) just as the FBI did against Apple to unlock passcode-locked iPhone in San Bernardino case in 2016. Yet, the court opinion here is not clear on this issue. It states, “after the execution of this warrant, the government may garner additional evidence…[and] can promptly apply for additional search warrants” and seems to assume that it can issue a search warrant after the seizure of a device.

If a warrant should be issued under the AWA, the threshold will be higher than the issuance of a search warrant. It requires “the absence of alternative remedies” and the consideration of such factors as “the closeness of the subject’s relationship to the criminal conduct and investigation,” “the burden the requested order would impose on the subject,” and “the necessity of imposing such a burden on the subject.”

In any case, requiring an additional warrant for fingerprinting might make the investigator impossible to unlock the Apple device since Touch ID only works for 48 hours.

As the court in Brooklyn case mentioned, the AWA is a general provision with a role of “gap filler” when “lack of laws” exists. It might be more appropriate to enact a law on forced fingerprinting in order to avoid ad hoc court decisions and to reflect public opinions on privacy interests in fingerprint itself which the Fourth Amendment does not protect and on the effectiveness of the investigations.