Last year I took Mom to get her driver’s license renewed. Everything was going fine until they tried to scan her thumb prints. Over the years, the thumb print on her dominant hand has been worn away. Erased. No matter how many times they tried, the machine was unable to scan a print. Surprisingly, we were told this was fairly common.

What, When, Where, How, and Why

When you touch something, you leave an invisible impression of your finger’s ridges. This impression is called a fingerprint. These ridges begin forming in the womb before you are born. Scientists aren’t completely sure how they’re formed, but they agree that genetics and environmental factors all influence their development.

Another factor is the skin itself. The body’s layers of skin grow at different rates. These layers can snag on each other as they’re stretched by the growing fetus. Because these factors always differ, each baby is born with fingerprints unique to them. (That’s ten unique fingerprints per person.)

There are several theories as to why we have fingerprints. One is that they help us hold things. Another is that they aid our sense of touch by improving tactile sensitivity and thus heightening tactile feeling.

Did You Know…

• Fingertips begin forming around the third month of pregnancy and are fully formed before the baby is born.
• No two people have the same fingerprints. Even identical twins’ fingerprints aren’t identical.
• Some people are born without fingerprints. This can be caused by these genetic disorders: Naegeli-Franceschetti-Jadassohn syndrome (NFJS), Dermatopathia pigmentosa reticularis (DPR), adermatoglyphia, and Ectodermal dysplasia.
• Some non-human animals have unique fingerprints, too, including gorillas, chimpanzees, and koalas.
• A koala’s fingerprints are almost identical to those of a human. The big difference? Koalas have two thumbs on each hand.

 Identification

A fingerprint’s size increases as a child grows into adulthood, but the fingerprint pattern made by the ridges never changes. So, since everyone has unique fingerprints, they can be used for identification.

The reason fingerprints don’t change is because they form deep in the layer of skin called the dermis. This layer of skin is resistant to decay and makes fingerprints almost impossible to change or lose. Injury can change them, as can plastic surgery, and while they don’t change with age, age can also affect them. As the ridges become thicker and the skin less elastic, it can be harder to capture fingerprints. Rough physical work—like laying bricks—and chemotherapy drugs can temporarily “erase” them, but left alone, they will return unchanged.

Did You Know…

• Dermatoglyph is the scientific name for fingerprints. In Greek, the word “derma” means skin and the word “glyphe” means carving.
• Fingerprints can remain, even after a person dies. They have been found on people who were buried hundreds of years ago.
• Being underwater doesn’t wash away fingerprints. They can still be found on weapons recovered from shipwrecks.

Law Enforcement

Fingerprints are one of the most reliable ways to identify criminals and solve crimes. This idea began in 1892 with a book written by British scientist Sir Francis Galton. Then, in 1896, Sir Edward Richard Henry developed a way to classify fingerprints into three general ridge patterns: loops, whorls, and arches. Law enforcement agencies around the world continue to use Henry’s method of classification, with only slight modifications made over the years.

Using computers, the matching of a specific individual’s fingerprints to those left at a crime scene is faster and more accurate than ever. Even so, an expert does the final verification of a fingerprint match. These specialists require extensive training. They must be proficient in using specialized fingerprint software, and know the fingerprint classification systems and advanced examination techniques.

Did You Know…

• Mark Twain saw the future of fingerprints in criminal investigations in the late 1800s. In 1883 and 1893, his books, Life on the Mississippi and Pudd’n Head Wilson, nabbed the fictional criminals using fingerprints.
• The first legal conviction based on fingerprint evidence in the U.S. happened in 1910. In the United Kingdom it happened in 1902. And the first case ever, took place in Argentina in 1892.
• Today, with special fingerprint powder, fingerprints can be “lifted” from almost any surface.
• The science of identifying fingerprints is called dactyloscopy. It’s the comparison and forensic analysis of fingerprints to identify an individual.
• Though other countries have set standards as to the number of fingerprint points that must be matched to claim a positive identification, there is no minimum in the U.S.
• In 2015, the FBI announced they were merging their criminal and civil fingerprint databases and making them all searchable.
• The FBI’s Integrated Automated Fingerprint Identification System (IAFIS) contains over 100 million fingerprint records.

That’s Not All

The use of fingerprints has been around for thousands of years, but it’s only been in the recent past that they’ve been used in criminal investigations and prosecutions. Yes, fingerprints identify people, criminals or victims who have been killed or injured, but they can do so much more.

Fingerprints are one form of biometrics—the measurement and analysis of a person’s unique physical and behavioral characteristics. Security measures use biometrics to authenticate who you are. Only the individual with the correct biometric fingerprint will have access to a cell phone, a gun safe, or a keyless door lock.

Today, the use of fingerprints brings biology, technology, and the law together. Who knows what tomorrow may bring?

Did You Know…

• The Chinese, possibly as early as 300 BCE, used fingerprints for business transactions and identification.
• In Ancient Babylon, contracts were sealed with fingerprints.
• Dermatoglyphics is a technique doctors use to diagnose medical conditions from fingerprints. Some of the conditions that can be diagnosed include Down syndrome, Sickle Cell disease, Autism, Alzheimer’s disease, and Parkinson’s disease.
• Experts can (with a high level of accuracy), use fingerprints to determine a person’s gender.