Fingerprints - Dermatoglyphics

What Are Fingerprints?  Raised ridges of skin

on the hairless surfaces of hands and feet (Dermal Ridges)

 Primates and other animals have them

 Provide traction and every ridge contains a gland

When Do Fingerprints Form?

 Begin to develop in the 10th week of gestation and are complete by the 24th week

 Chance, environment, and heredity all play a role in the development of an individuals fingerprints

Three Principals of Fingerprints

1.  A fingerprint is an individual characteristic a.  No two fingers have the same fingerprint b.  Identical twins are similar but not identical

2.  Fingerprints remain unchanged during a lifetime

3.  Fingerprints have general ridge patterns that permit them to be classified

Three Types of Fingerprints

Plastic Impressions.   Made in soft material like butter, soap, etc.

Visible Prints.   Prints made when fingers have been covered

in blood, dirt, oil, paint, etc. Latent Prints.

  Prints not visible to the human eye, hidden, unseen until treated.

Methods for Making Latent Prints Visible.

 Chemical Methods –  Iodine fuming – Ninhydrin – Silver Nitrate – Super Glue Fuming

 Powder Methods – Black Powder for light surfaces – White powder for dark surfaces

Dusting for Fingerprints

Three Classes of Fingerprints

What Is a Delta?

Loops   60% of the worlds

population has them   Ridges start on one

side, rise towards the center, and return back to the side they started from

  Has 1 delta   2 types of loops

•  Radial (thumb) •  Ulnar (pinkie)

Arches

  5% of the world’s population has them

  Start on one side, rise towards the center, then leave on the other side

  No deltas   2 Types of arches

•  Plain •  Tented

Whorls

 35% of the worlds population has them

 Has some ridges that form circles or spirals Has 2 Deltas

 4 types of whorls •  Plain •  Central Pocket whorl •  Double Loop •  Accidental whorl

Four Types of Whorls

Plain Whorl

Double Loop

Central Pocket Whorl

Accidental

Identify the Fingerprints

Identification of Minutiae  You must find 12

points of minutiae to match a print from a scene of a crime to a person’s print

 Label each with a number and a line to show its location

 Make a key at the bottom of the two prints

Examples of Minutiae

Identification of Minutiae

1.  Bifurcation 4. Ridge Ending 7. Bifurcation 2.  Bifurcation 5. Enclosure 8. Bifurcation 3.  Bifurcation 6. Bifurcation 9. Ridge Ending

Classification of Fingerprints

 Two International Systems  Henry System – Used in North America and

Europe  Vucetich System – Used in Central and South

America  Identification is based on class and ridge

patterns (minutiae) found on each individual print

Henry Classification System

 Five different levels of classification  Primary Classification

 Creates a fraction  25% of the world’s population is 1/1

  RI + RR + LT + LM + LL + 1 RT RM RL LI LR 1 Whorl = 16,8,4,2,1 Arch and Loop = 0

Primary Classification Example  A person has the following combination of

prints on their ten fingers: RT=Arch RI=Whorl RM=Arch RR= Loop RL=Whorl LT=Loop LI=Arch LM=Whorl LR=Whorl LL=Arch

RI/RT + RR/RM + LT/RL + LM/LI + LL/LR + 1/1

16/0 + 0/0 + 0/4 + 2/0 + 0/1 + 1/1 = 19/6

 The Primary Classification is 19/6

Use the Henry System Loop Arch Arch Whorl Loop

Arch Whorl Loop Loop Loop

Automated Fingerprint Identification System

Scan fingerprints into a computer database, which transforms it into digital minutiae. This is then used to identify unknown prints with several possible matches. In the end, a technician still makes the final ID of the unknown to the known print.