Fingerprint Samples & How to Classify Them

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Loops, Arches, and Whorls:

Loops	Arches	Whorls
A Loop starts and ends at the same side, which is the side of the opening.	An Arch goes from one side to another.	A Whorl is roughly circular, with the ridge lines going all the way around.
One Delta, on the opposite side of the loop's opening.	NO Deltas.	Two Deltas, on opposite sides of the entire whorl
All Images above were taken from: http://www.reachoutmichigan.org

NOTE the location of the Radius (thumb side; thumb = finger #1) vs. the Ulna (pinky side; pinky = finger #5)

 The direction of the opening of the loop is classified in terms of whether it opens toward the thumb or the little finger (rather than left or right); the name of that type of loop comes from the bone on that side of the lower arm (the radius and ulna). Based upon this, classify each of the prints below in terms of whether the print is a radial loop vs. an ulnar loop.

____________________________	____________________________

Classifying Prints, Part I:

A great resource for classifying prints:  http://www.policensw.com/info/fingerprints/finger07.html
Many of the images that follow are from that site.

First of all, we need to know the three basic types at the top of this sheet.  There are, however, some important general variations for each type.  We mentioned radial and ulnar loops above.  Arches also vary in that some have a central peak that "supports" the arch, and looks for all the world like a tent pole.  This is where the name "tented arch" comes from.

	versus
Plain Arch		Tented Arch
From: http://www.policensw.com/info/fingerprints/finger07.html

Whorls, on the other hand, are more complex.  A whorl is always characterized by at least two deltas (and whorls with more than two are specifically called accidental whorls).  The key to a true whorl is that an imaginary line drawn from delta to delta intersects a whorl line.  What follows are some variations of whorls:

Plain Whorl	Central Pocket Whorl	Double Loop	Accidental
From: http://www.policensw.com/info/fingerprints/finger07.html

The Primary Classification (The Henry System): In order to start classifying your set of prints, lets look at the group, as a whole.  Do you have any whorls?  Whether or not you have them, and where you have them, will allow us to categorize your group of 10.  First of all, the grouping is as follows, to form 5 pairs:

The presence of a whorl in any of the pairs above earns the value below the pair (i.e., a whorl on the Right Ring finger earns an 8 in the numerator, whereas a whorl on the left index finger earns a 2 in the denominator.  The absence of a whorl -- in other words you have either a loop or an arch -- earns a zero for that finger.).  Unlike actual fractions, we will be adding the numerators and the denominators, so it is best not to think of these as actual fractions!  We will also add a one to both numerator and denominator to get the final "fraction" classification:

There are 1024 possible groupings.  About 25% of the population has no whorls; they have only loops and arches.  Do you know what score they would have?  Write the fraction here: ____ / ____.  Enter your information in the table above, and calculate your score to the right.  Write your score on the board, and see if there is anyone else in the room with the same score.

Do the calculations ONLINE: http://shs.westport.k12.ct.us/forensics/04-fingerprints/henry_system.htm

Classifying Prints, Part Deux: Minutiae

Actual identification of a fingerprint as individual characteristic is based on the tiny details of the print, known as minutiae.

Basic and composite ridge characteristics (minutiae)
Minutiae	Example	Minutiae	Example
ridge ending		bridge
bifurcation		double bifurcation
dot		trifurcation
island (short ridge)		opposed bifurcations
lake (enclosure)		ridge crossing
hook (spur)		opposed bifurcation/ridge ending

Now let's look at an actual print to see some of the minutiae (and find the crease in the finger, and at least one other ridge ending):

This image is from http://perso.orange.fr/fingerchip/biometrics/types/fingerprint.htm

Now first classify the type of print, and then try to find as many minutiae as you can in the following two prints:

Type of Print: ______________________________	Type of Print: ______________________________