SFS2a. Identify and utilize appropriate techniques used to lift and evaluate readable, latent, plastic and visible

fingerprints. SFS1b. Distinguish and categorize physical and trace

evidence (e.g. fingerprints). T. Trimpe 2006 http://sciencespot.net

EQ

• How are fingerprints classified?

• What percentage of the population possess a particular patterns? Does the observed % equal the expected %?

• What are some potential reasons the observed patterns might not equal the expected?

WHAT ARE FINGERPRINTS?

• Friction Ridges – raised lines on skin that come together to form patterns also known as minutiae.– Designed by nature to provide our bodies with a

firmer grasp and resistance to slippage.

Fingerprint Principles

3 fundamental principles:

1. A fingerprint is an individual characteristic; no two people have been found with the exact same fingerprint pattern.

2. A fingerprint pattern will remain unchanged for the life of an individual; however, the print itself may change due to permanent scars and skin diseases.

3. Fingerprints have general characteristic ridge patterns that allow them to be systematically identified.

BASIC PATTERNS

1 2 3

Fingerprint Classes

There are 3 specific classes for all fingerprints based upon their visual pattern: arches, loops, and whorls.

Each group is divided into smaller groups as seen in the lists below.

LoopRadial LoopUlnar loop

Arch Plain arch

Tented arch

WhorlPlain whorl

Central pocket whorlDouble loop whorl

Accidental

8 DIFFERENT TYPES OF FINGERPRINTS

Remembered by:

L A W

Interesting Info

Did you know?Dactyloscopy is the study of fingerprint identification.

Police investigators are experts in collecting “dactylograms”, otherwise known as fingerprints.

Fingerprint Factoid: 60% of people have loops, 35% have whorls,

and 5% have arches

Arches -5%Arches are the simplest type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other. No deltas are present.

Plain ArchRidges enter on one side and

exit on the other side.

Tented Arches Similar to the plain arch,

but has a spike in the center.

Spike or “tent”

Loops-60%Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones.

Delta

Ulnar Loop (Right Thumb)

Loop opens toward right or the ulna bone.

Radial Loop (Right Thumb)

Loop opens toward the left or the radial bone.

NOTE: On the left hand, a loop that opens to the left would be an ulnar loop, while one that opens to the right would be a radial loop.

Whorls-35%Whorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental.

Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line, it is a central pocket whorl.

Plain Whorl

Central Pocket Whorl

Whorls – Part 2

Accidental Whorl

Accidental whorls contain two or more patterns (not including the plain arch), or does not clearly fall under any of the other categories.

Double Loop Whorl

Double loop whorls are made up of any two loops combined into one print.

Delta

Delta

Identify each fingerprint pattern.

Right Hand

Left Hand

Left Hand

Right Hand

Right Hand

A Closer Look at Fingerprints

Image from ftp://sequoyah.nist.gov/pub/nist_internal_reports/ir_6534.pdf T. Trimpe 2007 http://sciencespot.net/

COMPARISON OF PRINTS

• In identifying a fingerprint, the analyst must also look at ridge characteristics which are independent of the patterns (aka minutiae)

IDENTITY, NUMBER AND LOCATION IMPART

INDIVIDUALITY

Ridgeology: The study of the uniqueness of friction ridge structures and their use for personal identification.1 

1Introduction to Basic Ridgeology by David Ashbaugh, May 1999 Image from http://www.cs.usyd.edu.au/~irena/minutia.gif

The koala is one of the few mammals (other than primates) that has fingerprints. In fact, koala fingerprints are remarkably similar to human fingerprints; even with an electron microscope, it can be quite difficult to distinguish between the two.

As we have learned in our first lesson, a fingerprint is made of a series of ridges and valleys on the surface of the finger. The uniqueness of a fingerprint can be determined by the pattern of ridges and valleys as well as the minutiae points, which are points where the ridge structure changes.

Fingerprint IdentificationWhen minutiae on two different prints match, these are called points of similarity or points of identification. At this point there is no international standard for the number of points of identification required for a match between two fingerprints. However, the United Kingdom requires a minimum sixteen points while Australia requires twelve.

Automated Fingerprint Identification System (AFIS)

http://www.fdle.state.fl.us/CrimeLab/images/fingerrint%20comparison%20for%20afis.jpg

AFIS is a computerized system capable of reading, classifying, matching, and storing fingerprints for criminal justice agencies. Quality latent fingerprints are entered into the AFIS for a search for possible matches against the state maintained databases for fingerprint records to help establish the identity of unknown deceased persons or suspects in a criminal case.

Rid

ge C

har

acte

rist

ics

Use these characteristics as points of identification when comparing fingerprint samples. The more points you can find in common, the better the match!

http://cnx.org/content/m12574/latest/properties.jpg

Ridge Characteristics

Crossover

Core

Bifurcation (fork)

Ridge ending

Island

Delta

Pore

Scar

http://www.dkfz.de/tbi/projects/bmcv/images/iu_it246_04s_fingerprint1.jpg

How many ridge characteristics can you identify in this fingerprint?

• Uses computers to scan and digitally encode fingerprints so they can be subject to high speed computer processing.

• The computer determines the degree of correlation for both the search and file prints.

• A set of 10 fingerprints can be searched against a file of 500,000 ten finger prints in about 8/10 of a second.

• AIFIS has made possible the search of a single crime prints against an entire file’s print collection.

• Before AIFIS, police were usually restricted to comparing crime scene prints with known suspects.

• Now crime scene prints can be compared with all prints in a database.

• IAFIS has made possible the search of a single crime prints against an entire file’s print collection.

• Before IAFIS, police were usually restricted to comparing crime scene prints with known suspects.

• Now crime scene prints can be compared with all prints in a database.

1. Fingerprints are classified as LAW.2. In IAFIS, the presence or absence of whorls is

counted & recorded for identification primarily.

IAFIS Database System:

• Fingers are paired in the following sequence:

R. Index + R. Ring + L. Thumb+ L. Middle + L. Little +1=R. Thumb+ R. Middle + R. Little + L. Index + L. Ring +1

• If a whorl is found on the first pair, it is assigned a value of 16. The second pair 8, third pair 4, fourth pair 2 and last pair 1.

• All values are added, and 1 is added to both the numerator and denominator.

• (This is only one part of the classification, but it’s the only part we will cover in this class).

• Using the FBI system, classify a set of fingerprints where the right index and right middle fingers are whorls and the all of the others are loops.

• 16 +0+0+0+0+1 =

0+8+0+0+0+1

• 17

9

1. Using the FBI system, classify a set of fingerprints where the right ring and right little fingers are whorls and the all of the others are loops.

2. Using the FBI system, classify a set of fingerprints where the left middle and left ring fingers are whorls and the all of the others are loops.

3. Using the FBI system, classify a set of fingerprints where the left thumb, right thumb and left ring fingers are whorls and the all of the others are loops.

Fingerprint Evidence Collection

• EQ: How is fingerprint evidence collected?

Fingerprint Composition:

• A deposit of:– 98% perspiration (sweat= water + salts)– 1% amino acids– 1% oils

• Formed on the friction ridges of fingers, palms & feet

• These materials are left on the surface contacted

Inorganic Constituents (Salts) of fingerprint residue from sweat/oils:

• Major Components (Ions)Na+ K+

Ca2+ Fe2+

Cl- F-

Br- I-

HCO3- PO4

3-

SO42- NH4OH

• Minor Components (Ions)

Mg2+

Zn2+

Cu2+

Co2+

Pb2+

Mn2+

Organic Constituents of fingerprint residue from sweat/oils

Proteins

Amino Acids

Lipids

Glucose

Lactate

Urea

Pyruvate

Creatine

Creatinine

Glycogen

Uric Acid

Vitamin Sterols

Fingerprint Composition/ Skin Cross Section

• These inorganic & organic compounds allow fingerprint impressions to remain on an object.

• Different fingerprint development techniques that are attractive to specific chemicals left by fingerprints can be use to develop latent prints for visibility.

Types of Fingerprints Left at the Crime Scene

1. Latent print

2. Patent print

3. Plastic print

4. Katent print

Patent (Visible) Print

• Readily visible to the naked eye; residue print• Usually the result of some substance coating

the ridge detail & then allows the transfer of ridge detail to a surface that is touched.– Touching a surface after the ridges have been in

contact with a colored material.

• More common substances at a crime scene:– Blood, paint, grease, ink

• Photograph to preserve as evidence

Plastic Prints

• Visible print to the naked eye where the print detail is usually in a soft surface

• Impression left on soft surface.

• More common surfaces/substances seen at a crime scene:– Window putty, dust, dirt, mud, soap, dust

• Photograph to preserve as evidence

Katent Prints

• Prints made by pre-puberty children• Minutia more compact than adult,

therefore harder to ID specific points of identifications

• Not made by sweat remnants (sweat glands are not fully functional until puberty)

• Easy to lose on objects because mainly composed of water

Latent (invisible) Prints

• Prints not visible to the naked eye• result of perspiration or oils present on ridges • INVISIBLE: NEED DEVELOPING

* can be more easily developed on smooth, nonporous surfaces• Prints need to be made visible

– through: powders, chemical processes, or lasers

• Most common type of impressions left at crime scenes.

Recognition, Collection and Preservation of Fingerprint

Evidence • Recognition of fingerprint evidence is

similar to recognition of evidence in general – Training & Experience – Points of entry, weapons… MAY VARY CASE

TO CASE– Appropriate tools (Alternate Lighting)– Documentation- photo, notes, sketches

Recognition, Collection and Preservation of Fingerprint

Evidence• General Rule: objects believed to have latent

fingerprints should be collected intact & submitted– Necessary materials: brown paper bags, cardboard

box for firearms/weapons, manila envelopes for documents

• If item cannot be submitted to Fingerprint section of lab, must develop print at scene & use tape to lift or carefully photographed using 35mm or top quality digital cameras-scale

• REMEMBER: Marked/TAPE-SEALED/ CHAIN OF CUSTODY

Recognition, Collection and Preservation of Fingerprint

Evidence• Considerations for preservation of latent

print evidence– Is there biological evidence ?– Type of material on which the print is present

DEVELOPING LATENT PRINTS

• IN GENERAL:• - Powders are used to develop prints

on smooth, nonporous surfaces

-glass, mirrors, tile, etc.

- Chemicals are used to develop prints

on porous or absorbent materials like paper, cloth or wood; chemical reacts w/ residue (organic or inorganic) left from print.

-papers, cardboard, cloth, etc.

EFFECTS OF SURFACES

• Hard or glossy, non-porous surfaces retain latent impression fairly well

• Rough, coarse or porous surfaces do not receive or retain latent impressions well; textured glass or rough paint

* The age of a latent print can not be determined w/ any specificity except when the area was cleaned

Methods of Lifting PrintsNon-destructive Methods of

Lifting Prints:– Visual exams– Alternate light source

(ALS)– Photography

Destructive Methods:

• A.Physical Means (better for non-porous):– Conventional Powders,

Magnetic Powders, Fluorescent Powders

• B. Chemical Means (better for porous materials):– Ninhydrin, – Silver nitrate,– Superglue

(Cyanoacrylate ester),– Iodine fuming, – Physical Developer (PD),

1,8-diazafluorenone (DFO)

PHYSICAL TECHNIQUES: 1. POWDERS

• oldest & least sophisticated method for latent prints

• primarily used on non-porous material• Best when used in conjunction w/ Super

Glue Fuming technique* Over 85% of fingerprints developed by this method

Powder• MAKING A LATENT PRINT VISIBLE

• Place some powder on lid or are to be printed, not too much, make circular sweeping motion w/ brush , just grazing surface

Powder• LIFTING A LATENT PRINT ONTO A

FINGERPRINT CARD w/ TAPE; Place on CARD

Fingerprint card glossy side

Don’t forget info on other side!

What to include on lift card

• At a minimum include:– Case #– Date– Print #/letter– Initials of lifting

technician

Chemical Test1. Iodine Fuming: used for visualizing latent

prints by exposing them to iodine vapors. Not really a chemical reaction but a physical rxn; Temporary. Photograph print to preserve it.

2. Silver Nitrate (AgNO3(aq)): AgNO3(aq) reacts w/ salts that are present in sweat; expose to UV light to make visible.

Reaction: AgNO3(aq) + NaCl + UV 2 AgCl(s) + NaNO3(aq)

AgNO3(aq) + Cl- AgCl- + UV 2 AgCl 2 Ag0 +Cl20

• It’s the silver chloride (white) that shows up under UV light.

Chemical Test

3. SUPER GLUE (Cyanoacrylate) Fuming Technique:

• The cyanoacrylate gas will deposit on the proteins from your sweat to make a print.

• Develops latent print to produce white color print; White ridge detail is enhance by moisture.

• Best utilized on non-porous items or physical evidence.

• Contrast of print improved by application of dyes or powders.

Chemical Test

4. Ninhydrin-A chemical used to develop latent prints on porous materials by reacting with amino acids; turns print purple

5. Gentian violet (AKA-Crystal Violet): Reacts fat/oil left behind on print; stains purple.

Sample results for Ninhydrin