WhatsAppRedditShareEmailTweetPin0 Shares
The idea of using fingerprints in crime investigation and as a means of identification arose in the late 1800s. Before then, many cultures knew about the unique properties of fingerprints, and even ancient societies used fingerprints on clay as a means of identification.
The Babylonians used fingerprints and clay tablets for business transactions. It was obviously not as complex a process as it is today, and people didn't realize how unique fingerprints are and that they remain with a person for life, but they understood that they had a certain significance.
Fingerprinting has been an integral part of police work for years. Even if you've never had to deal with a criminal investigation, you've probably seen enough movies and TV shows to understand how the process works. A suspect leaves their fingerprints at a crime scene. The prints are processed, lifted, and compared to a database, after which the person is arrested based on their fingerprints. Since every person has a unique fingerprint, if it's found, you were at the crime scene. Pretty simple.
Have you ever wondered why fingerprints are unique? What is their function, and why do they vary so much from person to person? A lot happens right beneath your fingers, and some of the explanations are quite intriguing.
What is the purpose of fingerprinting?
It's difficult to appreciate the role fingerprints play at first glance or by touch. If you rub your thumb and index finger together right now, they'll probably feel quite smooth. Even knowing you have fingerprints, you won't feel their texture. However, paradoxically, the texture of your fingerprints is incredibly important for how you perceive the world.
For a long time, one of the common theories about why humans have fingerprints was that they provide grip or traction. They were compared to the tread of a car tire, and it was believed that, no matter how small, they create friction and therefore grip, allowing one to hold onto objects.
In fact, testing this theory has proven the opposite: fingerprints reduce friction between your fingers and the objects you're holding or touching. Fingerprints may improve traction in wet conditions, but testing this theory is actually more difficult than it seems, and there's no definitive answer.
Some studies show that moisture can even improve grip. Your fingers have many sweat glands, and when you squeeze a smooth surface, the sweat pores on your fingertips provide enough moisture for a good grip. Interestingly, the grooves in your fingerprints can also help you grip an overly damp object by allowing dirt and moisture to drain along these grooves, making your grip easier. You might still not be able to grip the object completely, but you'll be able to do so better than without fingerprints.
Another theory, which was more strongly supported by testing, was that fingerprints help us sense touch. Our fingers contain several mechanoreceptors that respond to touch, but one of them, located 2 mm below the fingerprint, is called a pacinian corpuscle. When biomimetic sensors were tested—one smooth and the other ribbed, as if it had a fingerprint—the fingerprinted version produced vibrations at the same frequency as the pacinian corpuscles, indicating that a fingerprinted finger would be much more sensitive to fine textures than one without them. The vibrations were 100 times stronger.
If you didn't have fingerprints, everything you touched would be a lot like touching the world with rubber gloves. Your ability to gather and interpret sensory information through touch depends largely on your fingerprints. Appreciating the subtleties of soft, smooth, rough, leathery, silky, or anything else is much more difficult without fingerprints.
Are fingerprints really unique?
We've all heard many times in our lives that fingerprints are unique. Nowadays, we take this for granted. Like snowflakes, no two are unique. However, it's worth considering what this means. Has anyone ever fingerprinted you? Your parents? Your best friend? If you take any 10 people, there are likely several who have never had their fingerprints taken before. And if that's true, how can we say with certainty that all our fingerprints are different?
This question may seem a bit pedantic, but the fact is that the claim that all our fingerprints are unique is more of a generalization than a proven fact. We consider them unique because every fingerprint we've ever recorded has been different from one another. It's logical to assume that they're all unique, and for the most part, they are. But we can't definitively claim that they all are, because there's insufficient data to support that claim.
The idea arose from the use of fingerprints as a method for solving crimes. It was seen as an absolute science. There was no need to rely on a witness who might see something in the dark and not be sure. There was no need to rely on assumptions. Prosecutors could bring to court a fingerprint from the murder weapon, and then a fingerprint lifted from the suspect during the trial, and present them side by side. There was no need to appeal to anyone's feelings or preconceptions. It was pure science, or at least that's how it was perceived.
As a pure science, fingerprinting was supposed to be infallible. This meant that no two fingerprints could be identical, and this idea was simply accepted as fact. This has been the case for over a hundred years. In 1894, Scientific American published a statement that the probability of two fingerprints being identical was one in 64 trillion. This means it would take over a million years before anyone would come along with fingerprints identical to yours.
One of the reasons DNA evidence is relied upon more than fingerprints to solve crimes today is the potential problems associated with fingerprints. For example, do you know how to tell two fingerprints apart? If they're incredibly different, sure. But what if two fingerprints are strikingly similar? You've probably seen in crime shows how fingerprints are outlined in small areas, those loops and whorls.
Fingerprint matching requires a match of these parameters, but standards vary across jurisdictions. Some require a match of 12 characteristics. In the UK, 16 was previously required, but in 2001, this number was changed to the number determined by the examiner, provided they could justify their conclusion. In the US, this can vary from country to country, and some countries have no established standards. Therefore, the number of matching points, if used at all, can be 6, 12, or 16, although 12 is the generally accepted value.
Considering that some fingerprints are partial or blurred, this job becomes even more difficult, and this method has been criticized for its infallibility.
No two people have ever been documented to have identical fingerprints. Therefore, it's entirely reasonable to claim that all fingerprints are unique. Even identical twins have different fingerprints. But without any specific standards for fingerprint comparison, there's a risk of convicting the innocent and acquitting the guilty because science isn't being applied as thoroughly as it should be.
One of the relatively recent advances in fingerprint comparison and analysis was made possible by artificial intelligence analysis. In 2024, it was discovered that similarities between fingerprints of the same person can be detected on different fingers. Previously, forensic scientists had overlooked this, but a computer was able to analyze different fingerprints and determine with up to 771% certainty whether two fingerprints belong to the same person, even if they were taken from different fingers.
This doesn't mean your fingerprints aren't unique. You wouldn't share your fingerprints with a complete stranger, after all. But it does mean they aren't unique to each finger, something forensic experts previously failed to understand. Or at least, not that unique.
Why are they different?
So fingerprints exist for a reason, which is good. But why are they so unique? Wouldn't it be easier if they were mostly the same? It's not like your genes put much effort into it, but it seems like it might be a waste of effort, if that's the right expression, to make them so unique for each person.
It turns out your fingerprints are a bit wild. Just as zebras develop stripes and leopards develop spots, you too develop fingerprints. Researchers studying fingerprint formation have discovered that they begin to form even before birth, in the epithelium. Before they develop into their current form, they resemble hair follicles. However, several genes are activated to form fingerprints, which function in a unique way compared to hair follicles.
Once activated, genes follow a Turing pattern. Turing's idea was that natural patterns, such as stripes and spots, could be the result of a pair of molecules working together. One is an activator, the other an inhibitor. They always work together, as if restraining each other and allowing these specific patterns to form and branch out, covering the entire organism or, in our case, the fingertips.
Active genes produce proteins that act as activators, while other proteins act as inhibitors, just as Turing hypothesized. The pattern begins in three places on the fingers: near the nail, right in the middle, and then down at the crease of the first knuckle. The pattern spreads from these locations, eventually merging to create a unique fingerprint that will differ from that of any other person. How and where it begins and spreads will always vary slightly from person to person, hence its uniqueness.
Do they ever change?
So, your fingerprints are unique when they're formed, but do they stay that way forever? Throughout a person's life, their appearance undergoes significant changes. Everything about you changes, so why don't your fingerprints change at all?
Your fingerprints change over time, just like the rest of your body. However, this doesn't mean you can avoid prosecution for crimes. An analysis of fingerprints taken over five years revealed some changes, but they are statistically insignificant. And when comparing fingerprints taken earlier and later, this is a negligible difference that no computer could ever undetect.
Even after 12 years, the matches were still within the margin of error. Computers can detect the difference, and you can certainly see that your fingerprints have changed, but that's still not enough to hope you can get away with a crime if you left fingerprints behind.
Fingerprint matching will only be problematic if the prints are of poor quality to begin with. That is, if it's a poorly scanned image or a partial print. This, combined with age, can certainly complicate fingerprint matching, but age isn't actually a determining factor.
A person can temporarily destroy their fingerprints by cutting them off, treating them with acid, or something similar. But your fingerprints will heal, and when they grow back, they will be as they always were. In short, your uniqueness will remain with you forever.
Other articles that may interest you