Fingerprint Uniqueness
What’s So Special About Your Fingerprints? | Wonderopolis
SCIENCE — Life Science
Have You Ever Wondered…
What’s so special about your fingerprints?
Do identical twins have identical fingerprints?
What is dactyloscopy?
Have you ever tip-toed into the kitchen to sneak a cookie out of the jar when no one was looking? Unless you wore gloves, you probably left behind evidence of your snack attack. A fingerprint expert could likely find fingerprints on the cookie jar and match them to the unique prints at the end of your ckily, most parents are neither fingerprint experts nor crime scene investigators (CSIs). However, the cookie crumbs on your chin might still give you away! Take a close look at your palms and the tips of your fingers. Do you see the tiny ridges and lines? If you pressed a finger onto an inkpad and then onto a piece of paper, it would leave a print of the lines and ridges on your finger — a fingerprint! Your fingerprints are unique. That means that no one else in the world has the exact same set of ridges and lines that you have on your fingers. Not even identical twins have the same fingerprints also stay the same from the time you’re born until death. Their uniqueness and lasting quality make fingerprints one of the best ways to identify a you realize that you don’t have to dip your fingers in ink to leave fingerprints? Sweat and body oils are constantly pushed out through tiny pores in our skin. These substances coat the ridges and lines of your you touch something, you transfer these substances to whatever you touch, leaving an impression of the ridges and lines on your fingers. These fingerprints — called latent fingerprints — usually can’t be seen by the naked eye. However, you can sometimes see them on certain objects, such as a glass ientists have known about these invisible fingerprints since the 19th century. As early as 1892, English scientist Sir Francis Galton wrote a book about using fingerprints to solve crimes. It was not until 1896, however, that Sir Edward Richard Henry would develop a way to classify fingerprints based upon their general ridge patterns: loops, whorls, and ‘s system of fingerprint identification — called dactyloscopy — has been modified slightly over time. Today, it is still used by law enforcement agencies all over the the last 100 years, advances in technology have helped law enforcement officers make even better use of fingerprints. Today, fingerprints can be “lifted” — identified and copied for later comparison — from just about any surface using special fingerprint reover, scientists don’t even need complete fingerprints any more. With the help of advanced computers and software, even half a fingerprint can be identified and matched with a comparison sample. Computers can even be used to make comparisons automatically, although final verification of a fingerprint match is still done by scientists who carefully study and compare the fingerprints to ensure a proper match is ngerprints aren’t the only thing scientists use to identify people, though. There are several different types of biological and behavioral characteristics — called biometrics — that can be used to identify an individual. Other examples of biometrics include DNA, the irises of the eyes, voice patterns, and facial patterns.
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Why do people have different fingerprints? | Ask Dr. Universe
Dear Mary,
Did you know even identical twins have different fingerprints? It can be hard to tell twins apart, but a close look at their fingertips can reveal who’s who. The reason lies partly in their genes, but mostly from the unique way everyone’s skin grows before birth.
That’s what I learned from my friend David M. Conley, a professor at Washington State University’s Elson S. Floyd College of Medicine.
“The reason fingerprints are unique is the same reason individual humans are unique, ” Conley said. “Variation is the norm, not the exception. ”
There’s no single cause for your unique fingerprint design. Instead, it’s the result of both your genes and your environment. This is called multifactorial inheritance.
Look closely at the lines on your fingertips. These are called “friction ridges. ” It’s hard to see, but they actually stick up above the rest of the skin.
“Fingerprints are impressions left behind when your fingers touch a glass, or when you put ink on your fingers and press them on a piece of paper, ” Conley said. “Friction ridges are the actual patterns on your fingertips and palms. ”
Friction ridges grow in different designs, like arches or whorls. If your parents’ fingers have a certain pattern, you might be likely to have it too. That’s because genes give the basic design, and you get your genes from your parents.
Genes are like instructions written inside the body. They give directions things like eye color, nose shape, and more. (Or, if you’re a cat like me, the length of your fur or the number of toes you have. )
Genes also tell the skin how and when to grow. Before a baby is born, they grow as a fetus inside their mother’s womb. The dermis (the inside skin layer) and epidermis (the outside skin layer) grow together. Friction ridges appear where these layers meet, guided by genes.
But these layers don’t grow at the same speed for every fetus. If one layer of cells grows faster, it can stretch and pull the others. As the fetus moves, their fingers can rub against the side of the womb.
These tiny forces push the skin as it grows. Together, they mold the direction of the growing ridges. The result is a unique fingerprint unlike anyone else’s.
Everyone’s skin grows in a slightly different environment. That’s why it’s so unlikely anyone has the same fingerprints as you – about a 1 in 64 billion chance.
Koalas and chimpanzees have unique fingerprints, too. Like humans, their hands and feet are covered in friction ridges. They also spend a lot of time climbing trees, just like humans’ primate ancestors did millions of years ago. That might mean friction ridges give texture to grab rough or slippery things.
Scientists don’t know yet if cats have different pawprints. But have you ever looked at the bumps on a cat’s nose? Some scientists think cats might have unique noseprints. I’m going to go check that out in the mirror later.
Sincerely,
Dr. Universe
No Two Finger Prints Are Alike – Sites@Rutgers
Since its invention in the 19th century, modern fingerprint identification has relied upon the assumption that by examining a person’s fingerprints one can identify that individual with certainty and to the exclusion of all others. This assumption has, in turn, rested on another assumption: that no two people have fingerprints that are exactly identical in terms of the form and configuration of their patterning. For example, we find a statement of this idea in the instructional materials of the University of Applied Science, an institution that provided training in fingerprint identification in the United States during the early decades of the 20th century:
There is one point of which we are absolutely convinced, and that is: no two finger prints are alike. We might take hundreds of thousands of prints from as many persons and there would be no two that we could call absolutely alike in every detail. There might be two or even many more of them that would have the same general design, but even then we would find on careful examination that they were vastly different, or so much so that we could easily point out the difference when we compare the two prints [1].
It was on the basis of this notion of the individual uniqueness of fingerprints that police, forensic experts, and prison officials have been so confident that they could identify individuals using this technique. It is important to be clear about what “uniqueness” means in this context, however. When people make the claim that fingerprints are unique to the individual, they do not mean that there are no two people with the same number or configuration of arches, loops, and whorls on their fingers, because, in fact, there are. These pattern-types are illustrated below.
Image: Harris Hawthorne Wilder and Bert Wentworth. Personal Identification: Methods for the Identification of Individuals, Living Or Dead. Boston: Richard G. Badger, The Gorham Press, 1918, 188. Public domain.
Rather, saying that no two people have identical fingerprints really means that no two people share identical configurations of fingerprint minutiae (referred to as “Galton details” in the accompanying image). A recent treatment of the subject defines minutiae as “[events] along a ridge path, including bifurcations (points at which one friction ridge divides into two friction ridges), dots (isolated friction ridge units that have lengths similar [to] their widths), and ridge endings (the abrupt end of ridges)” [2].
Image: Harris Hawthorne Wilder and Bert Wentworth. Badger, The Gorham Press, 1918, 125. Public domain.
Fingerprint minutiae are the minute characteristics of friction ridge skin that make the forensic use of fingerprint identification possible: even two people who have the same number of arches, loops, and whorls on their fingers will have different configurations of minutiae. As illustrated in the image below, fingerprint examiners can compare the types and locations of minutiae appearing in two fingerprints (or a crime scene fingermark and a fingerprint taken from a suspect) when attempting to determine if they came from the same person. Historically, this has been a commonly used approach in the field of latent fingerprint evidence.
Image: Francis Galton. Finger Prints. London: Macmillan and Co., 1892, Plate 15, Figure 22, following p. 96. Public domain.
For classroom handouts showing the different kinds of fingerprint pattern-types and minutiae, click here and here (courtesy of Kimberlee Sue Moran).
The idea that no two people have identical fingerprints has been a staple of the 20th-century literature on fingerprint identification. In 1920s China, for example, a fingerprint identification trainee named Chen Ruming explained the individual character of fingerprints in the following way:
Since all countries of East and West have been using fingerprinting, it has been put to the test repeatedly and two people with identical patterning have never been discovered. Thus we can know without doubt that people’s fingerprints are all different [3].
In this passage, Chen asserted that fingerprints can be viewed as unique due to the apparent fact that two identical fingerprints have never been discovered. This kind of argument has been common in the history of fingerprinting, as have others that are meant to “prove” (or at least assert) such claims about the individuality of fingerprints [4]. For example, some have used the observation that even identical (monozygotic) twins do not have identical fingerprints to make the same point. Whether or not such claims hold up is in some ways beside the point. Simon A. Cole has used the notion of the “fingerprint examiner’s fallacy” to describe the mistaken idea that the individual uniqueness of fingerprints could ever be taken as a guarantee of the accuracy of fingerprint identification. As Cole explains,
When asked by courts for proof of the “reliability” of forensic fingerprint evidence, fingerprint examiners answered that all fingerprint patterns are unique. Courts failed to grasp the gap in logic between the two statements and uniqueness became enshrined as the foundation of the accuracy of forensic fingerprint identification… We continue to labor under this fallacy today [5].
Cole’s point is that the uniqueness of fingerprints and the accuracy of fingerprint identification are two completely different questions. The ability to match a fingermark discovered at a crime scene with a fingerprint taken from a suspect is a complex process relying upon multiple levels of observation, analysis, and interpretation. Whether or not fingerprints are unique to the individual (in a general sense) tells us nothing about how the identification process is carried out and whether or not it is done accurately and reliably. In fact, these questions about the scientific validity, accuracy, and reliability of fingerprint identification are precisely the ones that are being most closely examined by researchers today.
Sources
[1] University of Applied Science. A Study in Finger Prints: Their Uses and Classification. Third Edition. Chicago: University of Applied Science, 1920, 59.
[2] Expert Working Group on Human Factors in Latent Print Analysis. Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach. U. S. Department of Commerce, National Institute of Standards and Technology, 2012, 2.
[3] Chen Ruming. “Zhiwen shengli zhi yanjiu” [Research on the physiology of fingerprints]. Zhiwen zazhi, no. 3 (1926): 59-64, quote from p. 62.
[4] Simon A. Cole. “Is Fingerprint Identification Valid? Rhetorics of Reliability in Fingerprint Proponents’ Discourse. ” Law & Policy 28, no. 1 (2006): 109–35.
[5] Cole, “Is Fingerprint Identification Valid? ”, 117.
Frequently Asked Questions about fingerprint uniqueness
What makes fingerprint unique?
There’s no single cause for your unique fingerprint design. Instead, it’s the result of both your genes and your environment. … Friction ridges grow in different designs, like arches or whorls. If your parents’ fingers have a certain pattern, you might be likely to have it too.Feb 7, 2020
Are fingerprints 100% unique?
When people make the claim that fingerprints are unique to the individual, they do not mean that there are no two people with the same number or configuration of arches, loops, and whorls on their fingers, because, in fact, there are.
What are the three unique main unique characteristics of fingerprints?
Fingerprint analysis looks at unique differences like the distance between different ridges, the heights of arches, the shape of whorls, and the length of loops.Jan 17, 2018
