How to Be a Cop: Learning to Fingerprint

We all know that law enforcement officials, whether it’s the feds or your local townie, use fingerprints as a main tool in identifying a person.

In fact, identifying a person by their fingerprints has been employed for over 2000 years, going back to Ancient Egypt. In 1858, Sir William J. Hershel was the first to document fingerprints while in India. From then on, the art of fingerprinting took giant strides. One of the most important advances being from Sir Edward Henry, who developed a classification system in 1896, that is still in practice today.

Henry’s classification was an advancement of Francis Galton’s, and narrowed down fingerprints into four general patterns.

1. Arch

This is when the ridges of a fingerprint run continuous without re-curving.  It was further broken down into two sub groups: the plain arch and the tented arch.

2. Loop

These fingerprints have ridges making a backward turn, but do not twist. The sub groups include the radial and ulnar loops.

3. Whorls

These feature prints that have two or more deltas. The four sub groups include: the plain whorl, central pocket, double loop and accidental whorl.

4. Composites

Fingerprints that include a combo of arch, loop and whorl patterns. Composites also have four sub groups: central pocket loop, twinned loop, lateral pockets loop, and accidental loops.

In 1924, Congress allowed the FBI to create an Identification Division. This allowed the government to easily file the prints of repeat criminals and missing persons. Today, of course, a computer system is used, but the concept remains the same.

The reason that fingerprints are so effective, and have been used throughout history, is because no two fingerprints are alike. Every person has their own distinct patterns and ridges.

While not everyone has their fingerprints on file, many of us. If you a driver’s license, a criminal record, or have applied for job, such as someone in security or a teaching position, then you’ve probably been fingerprinted.

Now that we’ve got a little history out of the way, let’s explore some of the science within fingerprints to help you fully grasp the importance of fingerprinting.

Types of Fingerprints

There are three types of fingerprints, patent, plastic, and latent prints, that are used during a crime scene investigation.

Patent Prints

These are simply visible prints to the naked eye. This occurs when the leftovers of a foreign substance on your fingers touch an object. For example, have you ever changed the oil in your car and then touched the white fridge for a beer? Did you happen to notice the new oily prints left behind? That’s patent prints.

Plastic Prints

These would be visible, and impressed, prints that happen when you press on a soft or malleable object. These objects are soft and then harden, such as  gum, blood, or a fresh coat of paint, which leaves a perfect print for investigation.

Latent Prints

These are those tricky prints that are invisible to the naked eye. These are obtained, since fingerprints always contain moisture, oil and/or grease, when we touch any sort surface.

How to Take Fingerprints

OK, so we’ve got the patterns and types of fingerprints out of the way, let’s show you how to take those all so important fingerprints.

You could always get the infamous black ink pad, which can be obtained at any craft shop. You could also visit, or maybe dish out the cash, for live scan for fingerprinting in the 21st Century.

But, let’s keep things simple, and show you how to take prints with everyday household supplies.

1. Shade in a dark area on a piece of white paper with a pencil point.

2. Press and rub you index finger in the the shaded area.

3. Take your marked finger and rub on the adhesive side of a piece of transparent tape.

4. Take the piece of tape with the fingerprint and tape it to a clean sheet of white paper.

5. Label each fingerprint on the paper so you know which print is from which finger.

6. Continue the above steps until all of the fingers and thumbs have been printed and labeled.

Some Helpful Tips

Here are some tips to help you get accurate fingerprints.

1. Make sure that the fingers are clean and dry. Use an alcohol swab for cleaning, and then dry them up. If your suspect has rough fingerprints, soften them up with some lotion first. Also make sure that the lotion is wiped away as well.

2. Have the subject stand about a forearms length away from the fingerprinting device. You stand behind them and to the right.

3. Grasp the subject’s hand with your opposite hand and make sure that they tuck in the fingers that aren’t being printed under their hand. Then guide their finger across the fingerprinting device.

4. Roll their finger across the ink, pencil mark, etc. until the tip of their finger is covered from nail to nail.

5. Roll fingers away from the center of the body, and thumbs toward, while taking the prints.

6. Once the print has been taken, carefully left the finger away from the pad to prevent smudges.

How to Dust for Prints

Finally, let’s show you how to dust for fingerprints, if you’re one of those paranoid people that swear someone is stealing your beer.

Now of course there are other ways of dusting for prints, but this is a method involving materials that you probably have lying around the house.

Or, you could pretend to be Tango or Cash, and get a real fingerprint dusting kit.

1. Take a balloon and fill half of it with water. Tie the balloon end off.

2. Hold the balloon, at the knot, over a lit candle for 15-30 seconds. The smoke from the candle will create soot on the balloon’s surface.

3. Collect the soot from the balloon using a brush.

4. Using the brush with soot on it, brush the object/area that you want to search for fingerprints. If you need more soot, just go back to the balloon over the candle trick.

5. Identify a fingerprint by looking for patterns or ridges on the object/area that you brushed.

6. Finally, collect the fingerprint. After you’ve located a fingerprint, place a piece of transparent tape over it. The print will stick to the tape.

Well, there you go. You know posse the skills for getting and searching for fingerprints. Until next time, happy hunting.

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