Fingerprint Samples & How to Classify ThemReturn to The Crime Lab

Loops, Arches, and Whorls: (Yes, it's the LAW!) - A Prelude to Primary Classification

Loops Arches WhorlsA 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 theridge lines going all the way around.

One Delta, on the opposite side of theloop's opening.

NO Deltas. Two Deltas, on opposite sides of theentire 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 radiusand 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: Primary ClassificationA 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 eachtype. We mentioned radial and ulnar loops above. Arches also vary in that some have a central peak that "supports" the arch, and looksfor all the world like a tent pole. This is where the name "tented arch" comes from.

versus

Plain Arch Tented ArchFrom: 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 twoare specifically called accidental whorls). The key to a true whorl is that an imaginary line drawn from delta to delta intersects a whorlline. What follows are some variations of whorls:

Plain Whorl Central Pocket Whorl Double Loop AccidentalFrom: 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. Inthe table below, classify each of your ten prints as to whether they are Loops, Arches, or Whorls.

R. Thumb R. Index R. Middle R. Ring R. LittleL or A or W L or A or W L or A or W L or A or W L or A or W

L. Thumb R. Index R. Middle R. Ring L. LittleL or A or W L or A or W L or A or W L or A or W L or A or W

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. Firstof all, the grouping is as follows, to form 5 pairs: NOTE: The ten prints as arranged on the print card, and the table above, areNOT in the same order as the Henry Table below.

R. Index R. Ring L. Thumb L. Middle L. Little

R. Index R. Ring L. Thumb L. Middle L. Little------ ------ ------ ------ ------

R. Thumb R. Middle R. Little L. Index L. Ring

16 8 4 2 1

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 thenumerator, whereas a whorl on the left index finger earns a 2 in the denominator. The absence of a whorl -- in other words you haveeither 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. Enter your information in the table below, and calculate your score to the right. Write your score on the board, and see ifthere is anyone else in the room with the same score.

RightIndex Right

Ring LeftThumb Left

Middle LeftLittle

AddedAutomatically

FINALGROUP

+ + + + + 1 ------ ------ ------ ------ ------ ------ = ------

+ + + + + 1Right

ThumbRight

MiddleRightLittle

LeftIndex

LeftRing

AddedAutomatically

FINALGROUP

There are 1024 possible groupings. About 25% of the population has no whorls; they have only loops and arches. Do you know whatscore they would have? Write the fraction here: ____ / ____. As each score is unique, we can also use the scores, as we will see inclass, to figure out which fingers have whorls. Can we say that the fingers without whorls definitely have loops? Why or why not?

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

Classifying Prints, Part Deux: Minutiae - Secondary ClassificationActual 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 1 bridge 7

bifurcation 2 double bifurcation 8

dot 3 trifurcation 9

island (short ridge) 4 opposed bifurcations 10

lake (enclosure) 5 ridge crossing 11

hook (spur) 6opposed

bifurcation/ridgeending

12

Taken from http://www.policensw.com/info/fingerprints/finger08.html Page Design © Ian Hunter.|

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

First classify the type of print below(__________________), and then try to label as many

minutiae as you can in the print.

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

Pores & Spots between the Friction Ridges: Tertiary Classification

Another way to identify prints is to look carefully at the details on and between the ridges. The image above left shows some of the detail in terms ofthe location of the sweat pores. For example, in addition to the sweat pore labeled above ("pore"), look at the line for the delta. There is an angledridge at the end of the line, and if you look carefully, you can see that there is a sweat pore exactly at the angle of the ridge. Below left, there is aprint in which you can fine spots between the friction ridges. The plastic print below right (an impression made in soft wax) shows the details one canfind between the ridges.