Biometric Systems and False Fingers

by Jennifer Rezny
on 22 July 2016
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On November 9th, 1969, the San Francisco Chronicle received a letter from the supposed Zodiac Killer providing details of his crime not yet known to the public. Between taunts, delusional statements of purpose and laborious descriptions of crimes, he noted his use of fingertip guards:

"2 As of yet I have left no fingerprints behind me contrary to what the police say in my killings I wear transparent fingertip guards. All it is is 2 coats of airplane cement coated on my fingertips -- quite unnoticible + very efective"

However, the Zodiac Killer case has also been subject to many embellishments and dramatizations that have elevated the story to almost mythic proportions. Many descriptions of the fingertip detail do not include the note that it was airplane cement, instead just suggesting that the Zodiac Killer employed false fingertips –– combined with the fact that fingerprints were indeed found and his own claim to have left false clues, it makes it sound as though the Zodiac Killer used artificial fingertips.

In 1969, this would be a bit of a stretch compared to contemporary forensic ability. The human fingerprint is a delicate, intricate thing: the papillary ridges on the palmar surface of the hands and feet are narrow but cleanly spaced, and they follow the curve of the fingertip in diverging paths. To create or sculpt a fingerprint to any degree of realism would take an absurd amount of specialized skill, much less to create ten and adhere them to one's fingertips and use them effectively.

Today, it isn't so difficult.

Enter biometric systems.

Computer science professor Anil Jain specializes in biometric systems –– high-tech security systems that employ the human body for identification instead of a password, such as facial-recognition systems, retina scanning and, of course, fingerprint scanners. With his Biometrics Research Group at Michigan State University, Jain takes scans of human finger prints and then 3D prints them. They do this in order to test existing biometric systems, find their flaws and ultimately strengthen them. Their work is centered on building stronger, harder to crack security: something crucial, considering the success they have had in tricking finger scanners with 3D printed fingertips. It's not a perfected science –– meaning not just anyone can whip up some printed fingerprints and go, Zodiac-style, into a life of crime –– but it's getting there.

Recently Jain's work took an interesting new twist, as reported by Fusion: law enforcement officers had seen his videos online, and turned to him for help with an ongoing case. A murder victim's phone could hold the solution to the murder, but with the phone locked by a fingertip scan, they have no way to access that information. Enter Jain: could he 3D print the victim's fingerprint to unlock the phone? 

The answer remains to be seen.

It seems that technology is advancing on all fronts, so it has begun a strange race. Forensics and security develop to protect us from fraud, forbidden access, and criminal actions, but at the same time, these same technologies grant us the ability to circumvent security measures and investigations. Almost fifty years ago, the Zodiac Killer created a workaround that successfully allowed him to elude identification with a few layers of glue, but he was up against magnifying glasses, old cameras and a paperwork system. Today, there aren't many reports of criminal use outside of spy movies, but people can already buy fake fingerprint kits for less than the cost of a fast food meal for the purpose of tricking their employer's finger-scanning time clock.

What we can be sure of, ultimately, is that the development of means to trick biometric systems will result in plenty of ethical questions. In another fifty years, if another Zodiac Killer should surface, what will the technological landscape look like? What systems would allow him to commit crime and law enforcement officials to investigate and prosecute him? Any measures we could take to prevent a serial killer could also encroach on civil liberties if law enforcement can immediately compromise any developments in biometric security, and yet efforts must be made to prevent crime. Movies like Minority Report play with the idea of a trade in retinas, fingerprints and faces, but they don't quite ask questions about the law's usage thereof. Minority Report's legal system wherein criminals can be charged with crimes before they are even committed proves to be false, but the narrative doesn't trouble the idea that law enforcement documents people by their retinas at all.

Once more, the answer remains to be seen.