We're all likely aware of the big Apple vs FBI case where the FBI wants to force Apple to open a back door in its encryption on iPhones, and we'll soon discover what the law will decide on that, but it got me thinking:

Obviously a subject could claim that he forgot his password, so that's a dead end, but with fingerprint scanners on new iPhones that leads to a few possibilities. Could the FBI legally do any / all of the following? Why or why not:

  • Retrieve fingerprints from a surface the subject makes contact with while in custody to artificially pass the fingerprint scan on an iPhone.

  • Force the subject to place his finger on the fingerprint scanner.

  • 1
    I think the first point will be fine, but the second one, not so much. I think the second one goes against the 5th Amendment of the Constitution.
    – scubaFun
    Mar 2, 2016 at 12:44
  • 1
    I agree with you @scubaFan and also note that for devices like the iPhone, if it's battery dies, or there are too many wrong finger print attempts, you need to manually the passcode. This makes it harder for police to just use some of the well publicized fingerprint hacks to get into a phone. Also, see my answer about forcing people to provide encryption keys: law.stackexchange.com/questions/7510/…
    – Mr_V
    Mar 2, 2016 at 14:22
  • In asking if the FBI can force the subject to place his finger on a fingerprint scanner, do you mean "might they be able to get a court order to force a person to provide prints?", or do you mean can they bypass the courts?
    – user6726
    Mar 3, 2016 at 2:02
  • @user6726 I didnt consider one specifically, but I'm curious about both ways. The former might seem obviously illegal, bypassing the courts, but I wouldnt be surprised if they were allowed to do it by some law. Mar 3, 2016 at 2:07
  • Okay, I have no idea, and I think it's worth asking.
    – user6726
    Mar 3, 2016 at 2:09

1 Answer 1


Here's what one recent law review article says:

While the privilege against self-incrimination bars compelling communications or testimony, compulsion that makes the suspect the source of physical evidence does not. Given that biometric authentication is merely a scan of physical traits that are compared to previously stored information, one can argue that compelled biometric authentication is not barred by the self-incrimination privilege. Indeed, the Supreme Court has repeatedly held that compelling an accused to demonstrate physical characteristics for identification purposes does not qualify as compelled self-incrimination because it is not testimonial in nature. Likewise, if an accused was compelled to place his finger on his laptop's fingerprint reader, or have his face scanned with his phone's facial recognition software, the physical characteristics would have been used for identification purposes and would likely not be considered "testimonial in nature" such that the scan would violate the self-incrimination privilege.

Erin M. Sales, The "Biometric Revolution": An Erosion of the Fifth Amendment Privilege to Be Free from Self-Incrimination, 69 U. Miami L. Rev. 193, 222 (2014) (citations omitted).

  • As a side-note and as someone who works on software security, this is (at least partly) why most devices will require you to enter your password rather than use a biometric scanner after a reboot or after having been inactive for a while Feb 1, 2022 at 14:39

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