Fingerprints- Reasonable Expectation of Privacy?

It wasn’t too long ago that a story hit the papers about a woman who used her sleeping husband’s fingerprint to unlock his phone. As she suspected, he was cheating on her- and on finding proof of his affair in his phone, she had such an enraged fit that the plane they were on had to make an emergency landing.

Link: Flight Diverted After Passenger Discovered Husband Was Cheating

Intrusion of Privacy

Although they were married, and in spite of the fact that the husband was actually cheating on his wife, the wife’s use of her sleeping husband’s fingerprint seems to fit all of the elements of the classic civil tort, Intrusion of Privacy. Intrusion of privacy occurs when (1) the defendant intrudes into the private affairs of the plaintiff; (2) a plaintiff has a reasonable expectation of privacy; and (3) the intrusion is highly offensive to a reasonable person. Considering the husband and wife have greater concerns (and the event did not take place in the United States), it’s unlikely that there would be any such action in court. However, this story helps us to think about privacy: do we have a reasonable expectation of privacy in our cell phones and the content inside, even from our spouse?

Reasonable expectation of Privacy from Government eyes

What about privacy from the government? Should the police be allowed to go through your phone, read your emails and texts, look at your photos (even those you deleted), and sift through your private messages on social media? The Supreme Court has firmly held that we do have a reasonable expectation of privacy in the digital contents of our cell phones, and that police must have a warrant in order to search them. Link: Riley v. California (2014) 134 S.Ct. 2473.

Warrant requirement

A warrant allows the police to search possibly all of those things on your phone, but here’s why a warrant is important. First, a warrant is issued by an impartial magistrate- one who has an overriding interest in both our individual Constitutional rights and in promoting legal justice and peace as a whole. Second, the warrant request by the officer to the judge must state probable cause. Probable cause requires the officer to have sufficient facts and circumstances as would lead a reasonable person to believe that evidence relating to criminal activity will be found in the location to be searched. There must be enough evidence to lead to a belief that criminal activity has or will take place.

Compelling a defendant to decrypt digital information

The 5th Amendment provides that no person “shall be compelled in any criminal case to be a witness against himself.” The issue is whether compelling a defendant to decrypt his digital content (by supplying a password or passcode) is requiring a defendant to be a witness against himself. Courts make a leap from witness to testimony and never look back: witnesses provide testimony, oral or written, and cannot be compelled to do so.

Last year, the Third Circuit Court of Appeals in Pennsylvania held that compelling a criminal defendant to decrypt his iPhone, Mac computer, and external hard drives was “a necessary and appropriate means of effectuating the original search warrant,” and that “for the purposes of the Fifth Amendment, any testimonial component of the production of decrypted devices added little or nothing to the information already obtained by the Government” Link: United States v. Apple MacPro Computer (3d Cir. 2017) 851 F.3d 238, 246-48. It’s interesting that the Court avoids expressly stating that digital content is not testimonial in nature, and gives some small hope for the future. However, the Supreme Court of the United States denied certiori in this matter, and no clarification or stronger holding is available.

In a similar situation, a Florida case, State v. Stahl, held that compelling a defendant to surrender the passcode to his phone was not testimonial in nature because it “did not compel defendant to communicate information that had testimonial significance under the Fifth Amendment’s protection against self-incrimination, providing the passcode would not be an acknowledgment that the phone contained evidence of video voyeurism, and the state had a warrant to search the phone” Link: (Fla. Dist. Ct. App. 2016) 206 So.3d 124, 128, emphasis added. Simply put, forcing a defendant in Florida to provide his passcode is not self-incrimination so long as there is a warrant, and so long as the defendant is not also forced to “acknowledge” the evidence in the phone. 

Touch-ID fingerprints to Unlock Phones

Recently, several courts have been asked to provide warrants to allow the police to seize the use of our fingers in order to unlock touch-ID fingerprint locks on our phones. This requires forcing the defendant to temporarily surrender their finger to be placed onto the phone in order to unlock it. The California case of Paytsar Bkhchadzhyan that has been popping up in legal blogs (link here) and professional interest forums over the last year, but is still unretrievable- either because the charges are still sealed or have still not yet been filed. Also see: Link to LA Times Article

Similarly, in an unpublished but retrievable case, one Federal District court in Illinois decided in September, 2017, that fingerprints are not testimonial in nature, and therefore do not belong within the Constitution’s 5th Amendment protections. For this Illinois court, the logic again is that witnesses provide testimony, which can be written or spoken. Fingerprints, like photographs, voice recordings, and blood draws in DUI cases are said by that court to be non-testimonial, and therefore are free from the 5th Amendment’s protections. There is a leap, however: providing access to encrypted phones is also providing access to all of the defendant’s statements, by email and “private” messages.


The issue has not yet been completely resolved, but so far American Courts have been leaning towards allowing warrant-carrying police to force defendants to decrypt their devices and to force defendants to unlock them with their own fingers. The Framers of the Constitution could not have imagined modern technology with fingerprints unlocking iPhones, or with password encryption of computer data. If they had, they may have worded the Fifth Amendment’s prohibition that no person “shall be compelled in any criminal case to be a witness against himself” in a way that would protect our rights more strongly.

I am keenly interested in this subject, and have only given a brief overview here. If you are interested in this area and would like to explore more, please see Wiki’s article on “Key Disclosures,” which gives a world wide overview of legal viewpoints.




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