Fingerprints 101

The Three Different Types of Fingerprints

The human population varies in how we all look; our outside defining characteristics. Some of us have brown hair, blonde hair, maybe we have freckles, no freckles, green eyes, or blue eyes; we’re all unique in our own way- including our fingerprints. If you look closely, you can see the outlines of your prints' ridges (raised lines) and furrows (recessed lines). What pattern do these ridges and furrows create? Maybe whirlpools? Hills? Teardrops? Or perhaps you see all three. The three types of fingerprints are:

1. Whorls (looks like a whirlpool)
a.) Plain
b.) Central Pocket loop
c.) Double loop
d.) Accidental loop

2. Arch (Looks like a hill)
a.) Tented
b.) Plain/Simple

3. Loop (Looks like a teardrop)
a.) Radial
b.) Ulnar

The most common of these prints are loops which make up about 60% of the population, whorls make up about 35%, and the least common, arches, which make up about 5%. The rarest of those is the tented arch.

Maybe you have mostly whorl prints-some double loop, some plain- and a few loop-shaped prints- mainly radial. But what if your neighbor or a family member has the same shaped patterns on the same fingers? Can scientists tell your prints and their prints apart? Well, good news, you won’t be getting charged with any of your neighbor’s crimes even if they have seemingly “identical” prints because, in reality, even if they look identical, they aren’t identical at all!

One must pay attention to more than just the print pattern when examining fingerprints, although this is an easy identifier. Remember the ridges and furrows we mentioned above? The raised and recessed parts of the fingerprint? Scientists carefully look at each print's details (the shape's position, how many ridges there are, the size of the furrows) to uniquely link someone to that print. There are so many tiny characteristics in each person’s fingerprint that they might look similar at first glance, but the reality is that no two prints are the same.

Latent Finger Prints Vs. Patent Fingerprints

Everything you touch throughout the day, your keyboard, phone, laptop, door handle, has your fingerprints all over it. You can even leave prints on your body… or someone else’s body (hence how bad guys are caught). Our fingerprints leave behind residues of oils in the shape of our ridges, and as we’ve established, each of these shapes is unique to the individual. These prints, known as latent fingerprints, are invisible to the naked eye since they were imprinted with only oil residue. In contrast, a patent fingerprint is visible to the naked eye because the finger was pressed into blood, paint, mud, etc.

Fingerprints on Porous Surfaces

Fingerprints are not only left on hard surfaces like countertops, door knobs, or weapons, but they can be left and lifted from porous items such as paper, untreated wood, or cardboard. How do we process fingerprints on such delicate surfaces?

Ninhydrin is the most common substance when lifting prints off porous surfaces. As mentioned earlier, the process of “lifting” prints is intended to make those fingerprints visible to the naked eye, but to do so, you must have the proper equipment. The right forensic equipment not only allows you to do your job but it keeps potential health and safety hazards at bay, such as skin, throat, and eye irritation caused by the emission of smoke and fumes.

One search on YouTube will give way to hundreds of “DIY” videos on how to lift fingerprints in the comfort of your own home. These videos help grasp how we identify prints and are fun science experiments. However, having the correct equipment in your labs is essential if you want your evidence to hold up in court. With the Mystaire MY-8000 humidified incubator (Ninhydrin Acceleration Chamber), the development time for ninhydrin processed evidence (on porous surfaces) can be perfected. But first, what is ninhydrin, and how does it work?

When the sweat (amino acids) left from a suspect or victim’s finger mixes with a lab’s working solution of ninhydrin, a bright purple color called Ruhemann’s Purple will appear. But heat and humidity must be applied for this bright purple to form, revealing your suspect’s prints. If you were processing these prints, after you put the ninhydrin solution on, you would place the paper or whatever porous item you have in Mystaire’s Ninhydrin Chamber, which hastens the development time, giving you faster results. Not only are the results faster, but this machine has unique features:

1.) Provides control of humidity from 50-80%
2.) Provides heater control between 30°-50°- C
3.) Stainless steel exterior and interior liner
4.) Epoxy-coated wire shelves
5.) Casters form
6.) Fluorescent lamp

At the end of processing, your prints should be Ruhemann’s purple, which we discussed above. Your final step is to compare those prints with your suspect to see if you have a match!

Our Ninhydrin Acceleration Chamber comes in two different sizes with voltage options of 110v or 220v. Fill out a contact form today to get in touch with a team member to help your lab find the right size and voltage option for your laboratory’s needs.