How Fingerprints Changed Policing Forever

How Fingerprints Changed Policing Forever

When I was in first grade, my father came to my school in his police uniform to talk about fingerprinting. I remember how proud I was to see him up there in front of all my classmates–my dad, the policeman! After he talked a little bit about his job, he showed us how the police take fingerprints and then we each had a turn rolling our fingers on a form, which would then be given to our parents.

Turns out, in the 80s, this was a popular idea. In October 1982, President Reagan signed the Missing Children’s Act, which, according to the New York Times, “set up procedures for parents of missing children to file information with the Federal Bureau of Investigation so it can be fed into the F.B.I.’s National Crime Information Center computer.” Although there was some pushback, the intention was to provide a way for authorities to find missing children. Say, for example, a child is abducted by a parent in a domestic dispute, he/she may be identified later when providing a fingerprint for a driver’s license. Or, if a child runs away, his/her parents can give the police the child’s fingerprints and if that child is picked up for a crime three states away, they’ll be identified based on their fingerprints as the missing child.

When was fingerprinting figured out?

Fingerprinting may have become popular in the 80s following Reagan’s bill, but it evolved almost 100 years before, in the late 1880s. Prior to 1890, if a crime scene revealed no easily identifiable clues, the police would often rely on the tedious “needle in the haystack” technique, which involved going door to door to talk to people in hopes that someone knew something. Not only was this time consuming, but with the lack of modern transportation, a policeman had to be really dedicated.

By the 19th century, cities expanded, and with the expansion, crime rates rose. Most crimes, however, were committed for economic reasons. Thievery or burglary for the lower classes, reputation control for the upper (like getting rid of an unwanted mistress). This meant that police were faced not with solving crimes per se, but rather identifying habitual offenders.


Louise-Adolphe Bertillon, a French police officer, was the first to classify humans into statistical groups based on the fact that all humans have at least something in common. He thought that if he could devise a series of measurements–like, say, the length of the head or the forearm–he would be able to classify criminals and thus identify habitual offenders.

Louise-Adolphe Bertillon

After some pushback from local police, Bertillon was finally given the chance to showcase his new system. He settled on 11 measurements of various parts of the human body, based on the assumption that there’d be little chance two men would have identical measurements. Each person’s measurements were written on cards, much like a card catalogue at the library. Unlike a card catalogue, however, there was no Dewey Decimal System for organizing these measurements. As criminals were measured and photographed, the volume of cards grew. As the volume of cards grew, police would spend hours and sometimes days going through each card looking for a particular measurement and/or criminal.

But hang on, let’s break it down.

Let’s say for example my suspect’s head was 32 inches in circumference. As a detective, I would go to the medium size head drawer to search through the cards of men with 32 inch heads. From there, I’d match other characteristics or measurements. If I found a card that matched him, I could identify him, blow any aliases he may have been using, and book him for the crime.

If I didn’t find a card that matched, I’d add his measurements and photograph to my catalogue for future reference.

It was a long, tedious process, and while Bertillon was on the right track, he wasn’t quite there yet.

In the 1820s, a professor of anatomy, Johann Purkinje, had shown that no two fingerprints were the same. By 1858, fingerprints were used to help prevent pensioners from collecting twice on their pensions.

Then in 1879, the first recorded use of fingerprinting was used to clear a man of suspicion of robbery. A sooty fingerprint was found at the scene but when the accused man gave his fingerprints, they didn’t match the one left behind. Soon thereafter, another man confessed to the crime.

Despite these early successes, it took some time for police to catch on. While the school of thought pioneered by Bertillon was gaining in popularity (and in fact took on a life of its own, becoming known as bertillonage), police weren’t wholly convinced. Fingerprinting, like bertillonage, had run into its own classification problems.

How do we classify this shiz again?

Sir Francis Galton wrote the first book on fingerprinting in 1892. When Scotland Yard was looking to adopt either bertillonage or fingerprinting as a way to help classify criminals, they were impressed by the simplicity of Galton’s findings but the lack of a classification problem still stood in the way.

This is where Inspector General of Police in Nepal, Edward Richard Henry, comes in.

Edward Richard Henry

Henry recognized that there are characteristics that all fingerprints share.


The tiny ridges that make up a fingerprint are first formed in the womb by pressure on the baby’s fingers. These ridges contain pores. These pores sweat. And it’s this sweat that’s responsible for fingerprints being left behind on nearly everything we touch.

All of these ridges form Patterns. These patterns can be classified in three ways.

Loops, whorls, and arches.

In the late nineteenth century, these patterns were known to scientists and police, but what was the best way to classify these differences? Should they look at the whorls? Or what about the loops, which curve both outward toward the thumb and inward toward the index finger.

Take a look at your fingerprint. At the top you see parallel lines, then toward the center these lines turn into eddies and whirlpools. These eddies form long loops (which curve outward and inward). Between the loop and the arch of the parallel lines above and around it, you get some “leftover” space triangular in shape. These are called the “deltas.”

Henry measured the deltas and fixed a limit on the inner and outer edges of the triangle. From there, a line could be drawn between the two points. Then the papillary lines that it intersects with counted. It was this number that allowed police to classify fingerprints.

All a detective had to do when presented with a new fingerprint was decide which group it belonged to (loops, whorls, arches), and then count the lines.

Once Henry figured out a way to classify our fingerprints, fingerprinting became an integral part of police work, slowly beating out bertillonage as the primary means of identifying criminals.


By the end of the 1910s, fingerprinting was widely used, and by the late 1920s, fingerprints were even being transmitted through wireless telegraphy. Also starting in the 1920s, the FBI created its first identification department that established a central repository of criminal identification. And that brings us up to the present: in 1999, the Integrated Automated Fingerprint Identification System (IAFIS) was put in place.This computer repository contains the fingerprints of more than 135 million criminals and civilians.

The fingerprint card I made with my father back in grade school is probably with my parents in Kendra’s Folder, along with my Homemade Lobotomy Kit, but a lot of those collected were held at local police stations in case of emergency. And while we now have DNA to help identify criminals, we should not discount the importance of fingerprints, which still help prove crimes the world over.

Have fingerprints impacted your life? Let me know below!

Sources used for this article:

Written in Blood: A History of Forensic Detection by Colin Wilson and Damon Wilson

New York Times archive article 

History of AFIS

How Stuff Works 

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