Flinn Fingerprinting Kit
Catalog No. AP7612
Publication No. 7612
Introduction
The fingerprint is still one of the most important and useful pieces of forensic evidence. No two persons’ fingerprints are alike, not
even identical twins. This uniqueness allows fingerprints to continue to be strong evidence for identification of individuals at crime
scenes.
Concepts
• Ridge patterns
• Loops, whorls, arches
• Fingerprint classifications
Background
What is a fingerprint?
Human skin (see Figure 1) represents the body’s first line of defense against
foreign invasion and infection. Skin is composed of an epidermal outer layer and a
dermal inner layer. The surface between the epidermis and dermis is usually uneven,
because the epidermis has ridges projecting inward and the dermis has finger-like
papillae passing into the spaces between the ridges. This uneven boundary area is what
contains the friction ridge structures responsible for our one-of-a-kind fingerprint
patterns. These ridge patterns begin to form in the eighth gestational week and remain
unchanged throughout the individual’s life.
Sweat glands are located in the dermis and their ducts extend up through the
epidermis where they release perspiration, oils, and other materials through sweat pores.
The perspiration, oil and salts from these sweat glands leave an identifiable residue
conforming to the pattern of an individual’s fingerprints.
Fingerprint Patterns
There are three main fingerprint patterns, each having various sub-groups, found in the human population:
Loop (65%)
Radial loop
Ulnar loop
Whorls (30%)
Plain whorl
Central pocket whorl
Double loop whorl
Accidental whorl
Arches (5%)
Plain arch
Tented arch
These three main categories were first published in a book titled Finger Prints by a nephew of Charles Darwin. Sir Francis
Galton’s book, published in 1892, served as a foundation upon which modern fingerprint techniques are based.
A Loop pattern has one or more ridges entering from one side, curving, and then leaving the
same side it began, as illustrated in Figure 2. Loop patterns always develop ridges that diverge to
form a delta. It resembles a “Y” pattern. All loops must have one delta.
A Loop pattern on a fingerprint card that opens toward the thumb is a radial loop. A loop
pattern that opens opposite the thumb is an ulnar loop, as shown in Figure 3. Remember, a
fingerprint record is a mirror image of the actual fingerprint.
Whorls are friction ridge patterns that have a minimum of two deltas as illustrated in Figure 4.
There are four whorl sub-groups: plain, central pocket, double loop, and accidental.
The plain whorl has two deltas and a complete ridge circuit. It is almost a “circular” pattern.
The central pocket whorl differs from the plain whorl in one of the delta areas as shown in Figure
4. The deltas are not symmetric and one side appears to be stretched like elastic (shown by the
smaller circle).
The double loop whorl (see Figure 5) is composed of two loops and two deltas. The last whorl
sub-group is the accidental (Figure 5). This pattern is defined as a “pattern consisting of a combination of two different types of
patterns, with the exception of the plain arch with two or more deltas or a pattern which possesses some of the requirements for two or
more different types, or a pattern which conforms to none of the definitions.”
Arches (see Figure 6) are friction ridges that enter on one side of the finger and cross to the other side while rising upward in the
middle. The simplest is the plain arch with mild bulging. The tented arch appears to have a spike acting as a pole in the middle.
Individual Ridge Characteristics
There are six ridge characteristics: trifurcation, bifurcation, short ridge, enclosure, dot (or island), and ridge ending as shown
in Figure 7.
Fingerprint Classification
Fingerprints are analyzed and classified a number of different ways to expedite retrieval and identification. The recognition
of the ridges, their relative number, and approximate location are key to identifying the print with the individual. There are at least
150 individual ridge characteristics on the average fingerprint. The greater the number of identical matching points on a fingerprint
the greater the chances of the match. In a judicial proceeding a point-by-point comparison is usually made graphically to convince the
jury of a match.
A preliminary classification method, which is only a very small part of the FBI classification method, is based upon whorl
patterns of all ten fingers. The classification begins by identifying the presence of any whorl patterns. Whorl patterns are assigned a
numerical value based on the finger on which the whorl is found. The formula and values are outline in Figure 8.
The values for the top row are added and become the numerator. The
values of the bottom row are added and become the denominator. The results
are expressed as a fraction. The preliminary classification for an individual
with only one whorl, which is on his right index finger, would be:
This preliminary classification is just one of many sorting methods used by FBI computers to narrow the number of possible matches
to suspects. New computer scanning techniques will rapidly be replacing these older classification methods.
Activity A. Fingerprint Classification
Materials
Fingerprint Card Set
Procedure
1. Use the Primary Classification Worksheet to record your classification of each fingerprint from A through R.
2. Do not write on the Fingerprint Card Set. Classify each print as loop, whorl or arch. Use as many subcategories as possible.
Refer to the Background section as needed.
Activity B. Matching Crime Scene Fingerprints
Materials
Crime Scene Fingerprint - Fingerprint Card Set
Procedure
1. Determine if there is a match between any of the known suspects and prints on the Fingerprint Card Set. Find at least one
individual ridge characteristic that clearly matches the suspect to the crime scene print.
3. Record your findings on the Primary Classification Worksheet. Record your suspect’s fingerprint number and defend your
choice.
Activity C. Inked Fingerprints
Materials
Access to soap and water Ink pad
Fingerprint Record Sheet Scratch paper
Procedure
Making good, clear inked fingerprints requires practice and deliberate work. Pressing too hard or using too much ink may smear
the fingerprint. Practice on scratch paper before making your actual print record.
1. Starting on the left side of your right index finger, gently and uniformly roll your finger to the right side of the ink pad.
2. On scratch paper, place the left side of your inked finger down.
3. Grasp this finger with your left thumb and forefinger and gently roll to the right side while maintaining uniform pressure to the
finger to avoid smearing.
4. Repeat this procedure for your right hand fingers until your print is of acceptable quality for fingerprinting on the Fingerprint
Record Sheet.
5. Fingerprint the fingers on your right hand on the Fingerprint Record Sheet.
6. Repeat the same procedure for the fingers on your left hand with a rolling motion from left to right. Use your right thumb and
forefinger to guide each finger during the process. Remember to maintain uniform pressure to the fingers to avoid smearing.
7. Set the Fingerprint Record Sheet aside to let the ink dry completely.
8. Wash your hands thoroughly with soap and water.
9. Refer to the Fingerprint Background Information and do a preliminary FBI number classification for your personal fingerprints.
Record your results on the Primary Classification Worksheet.
Activity D. Latent Fingerprints on a Non-porus Black Surface
Materials
Camel hair brush Lifting tape, 3 inches
Construction paper, black, 1⁄6 sheet White dusting powder
Damp cloth
Procedure
1. Find a clean area on a black lab table and gently press your thumb down on the table edge to leave your thumb print. Hint: If
necessary, run your fingers through your hair several times to increase the amount of oil on your fingers in order to leave a
latent print.
2. Use the brush to gently “float” a small amount of white dusting powder onto the latent print area. Be sure to add the powder very
slowly—until you can see the print clearly. Do not add so much powder that you fill in the space between the ridges.
3. Once the print is visible, gently brush in the direction of the friction ridges to avoid smearing.
4. Obtain about 3 inches of lifting tape. Adhere the tape to the base of the print (edge of table). Holding the tape taut and beginning
at the base of the print, gently begin pressing down the tape as it moves upwards and beyond the print. Try to avoid air bubbles
and smearing.
5. Gently pull back the tape, lift the print, and place the print on one half of the piece of black paper. Label the print with your
name. Your partner should do the same with the other half of the paper.
6. Wipe the table with a damp cloth.
Activity E. Latent Fingerprints on a Non-porous Surface
Materials
Access to soap and water Glass slide
Black dusting powder Lens paper
Camel hair brush Lifting tape, 3 inches
Damp cloth White paper, 1⁄6-sheet
Procedure
1. On a clean, dry glass slide, gently press your thumb down leaving a fingerprint. Hint: If necessary, run your fingers through your
hair several times to increase the amount of oil on your fingers in order to leave a latent print.
2. Use the camel hair brush to gently “float” a small amount of black dusting powder onto the latent print area. Be sure to add the
powder very slowly—until the print is clearly visible.
3. Once the print is visible, gently brush in the direction of the friction ridges to avoid smearing.
4. Obtain about 3 inches of lifting tape.
5. Adhere the tape to the base of the print. Holding the tape taut, gently begin pressing down the tape moving upwards until the tape
is adhered beyond the top edge of the print. Note: Avoid creating air bubbles and smearing. If a mistake is made, begin again.
6. Gently lift the tape and print from the glass slide. Place the print on one half of the piece of white paper. Label the print with
your name. Your partner should do the same with the other half of the paper.
7. Wash the glass slide with soap and water. Carefully dry the glass slide with lens paper. Wipe the table with a damp cloth.
Cleanup and Disposal
Wash all surfaces with soap and water. Most of the ink used for fingerprints will wash off initially with soap and water. Minute traces
of ink remaining will be gone in a day or so.
Activity F. SuperGlue Fuming
Catalog No. AP7402
Publication No. 7402
Introduction
Perform one of the newest fingerprinting techniques currently used by many police departments—SuperGlue fuming! In this
technique kit, the fumes from ordinary SuperGlue are used to “develop” and preserve fingerprints left on a non-porous surface.
Materials (for each set up)
Sodium hydroxide solution, NaOH, 0.5 M, approximately 10 mL*
Aluminum foil dish*
Beaker (or similar container)
Cotton ball*
Fuming chamber and lid*
Super Glue, 3 to 4 drops*
Magnifying glass, dual lens*
Microscope slide, glass*
Paper towel
Tongs or forceps
Safety Precautions
Sodium hydroxide solution is a hazardous and corrosive liquid; it is dangerous to eyes and can cause skin burns. Avoid contact of sodium hydroxide and Super Glue
with eyes and skin. Super Glue fumes may be irritating. Perform this activity in a well ventilated area. Wear chemical splash goggles, chemical-resistant gloves, and a
chemical-resistant apron. Do not wear cotton gloves when performing this activity—Super Glue generates heat when reacted with cotton. Wash hands thoroughly with
soap and water before leaving the laboratory. Please follow all laboratory safety guidelines.
Preparation (Done the day before)
1. Obtain at least one cotton ball for each fuming chamber and the 0.5 M sodium hydroxide solution.
2. Place the sodium hydroxide solution into a beaker or similar container.
3. Using tongs, dip each cotton ball into the 0.5 M sodium hydroxide solution. Handle the cotton balls carefully—sodium
hydroxide is corrosive to eyes and skin. Note: Prepare enough cotton balls for the number of fuming chambers that will be
set up.
4. Place the sodium hydroxide–soaked cotton balls aside to dry completely. It is best to allow the cotton balls to dry overnight.
Procedure
1. Obtain a Super Glue fuming chamber and lid, aluminum dish, tube of Super Glue, presoaked cotton ball, a microscope slide, a paper
towel, and a magnifying glass.
2. Place a moistened paper towel on the bottom of the fuming chamber.
3. Place the aluminum foil dish in one of the corners of the fuming chamber.
4. Place one of the cotton balls presoaked with sodium hydroxide in the aluminum dish.
5. Obtain a microscope slide. Rub a finger against your nose or forehead and make several fingerprint impressions on the
glass slide.
6. Place the slide with the fingerprints in the fuming chamber so that the surface that contains the latent prints is facing the
cotton ball in the chamber.
7. Add three or four drops of Super Glue to the cotton ball and immediately place the lid on the fuming chamber. The cotton
ball should begin to emit fumes within a few seconds. Allow the fingerprint development process to continue for 15 minutes.
8. After the development of the fingerprint(s) is complete open the container in a well-ventilated area and remove the slide.
9. Place the slide on a clean, flat surface and examine it with the magnifying lens. The fingerprints will be “fixed” to the slide
and prominently displayed as crystalline white traces.
• Acetone may be used as a solvent to clean up Super Glue spills.
Discussion
Cyanoacrylate is the generic name for glues containing methyl-2-cyanoacrylate. These are typically sold under trademarks
like SuperGlue and KrazyGlue. Cyanoacrylate adhesives are classified “instant adhesives.”
In most cases, cyanoacrylate is an acrylic resin that rapidly polymerizes in the presence of water to form long, strong
chainlike molecules—these are the forces which join the bonded surfaces together. Because the presence of moisture causes the glue
to set, exposure to moisture in the air can cause a tube or bottle of glue to become unusable over time. Cyanoacrylate sets quickly,
often in less than a minute. A normal bond reaches full strength in two hours and is waterproof.
Super Glue fuming is a process in which items are placed into an airtight chamber and exposed to Super Glue vapors.
Common chambers that are used for Super Glue fuming are fish tanks, plastic bags and other specifically designed chambers that
are commercially available. When vaporized, Super Glue reacts to the amino acids, fatty acids and moisture in fingerprints. As a
result, fingerprint “residue” often turns white and becomes polymerized—or bonded—to the print surface.
In this activity, Super Glue will be placed on an absorbent cotton ball presoaked with sodium hydroxide creating an
exothermic reaction. The heat generated from this reaction speeds up fuming and allows the fingerprints to be developed within
minutes. This “chemical acceleration Super Glue fuming method” is often is used by police departments for field applications on
containers that may have contained drugs, tools found at a crime scene, and beverage containers, such as bottles or cans.
Non-chemical acceleration heat generation is another Super Glue fuming method that is commonly performed. Safe heat
sources such as a 60-watt lightbulb placed outside of the fuming chamber or a coffee cup warmer placed inside the fuming chamber
may be used to accelerate fuming without using sodium hydroxide and cotton balls. This process generally takes hours instead
of minutes. Heat sources to avoid due to safety concerns and because they generate too much heat include soldering irons and hot
plates.
Samples may also be fumed using Super Glue in vacuum chamber. The vacuum chamber technique involves removing all
of the air from the chamber with a vacuum pump. This reduces the atmospheric pressure and allows the glue to fume in a short
amount of time. This technique also allows the Super Glue fumes to penetrate into small crevices. Using a vacuum chamber is
perhaps the best technique for many surfaces. As an example, if a plastic bag is fumed in a vacuum chamber, fingerprints may
develop even on the inside of the bag.
Fingerprint Lab Grading Rubric
Grading Rubric: Activity A
Grade # Correct
A+
18
A
16-17
A15
B+
14
B
12-13
B11
C+
10
C
8-9
C7
D+
6
D
4-5
F
≤3
Grading Rubric: Activity B
Grade # Correct
A+
23-24
A
21-22
A19-20
B+
17-18
B
15-16
B13-14
C+
11-12
C
9-10
C7-8
D+
5-6
D
3-4
F
≤2
Grading Rubric: Activity C
Activity
Weight
Calculation #1
1.0
(.2 for each)
Calculation #2
1.0
(.2 for each)
Essay #1
1.0
(2 part ans.)
Essay #2
1.0
(3 part ans.)
Grade Points
A+
3.7-4.0
A
3.4-3.6
A3.1-3.3
B+
2.7-3.0
B
2.4-2.6
B2.1-2.3
C+
1.7-2.0
C
1.4-1.6
C1.1-1.3
D+
0.7-1.0
D
0.4-0.6
F
≤0.3
REPORT SHEET FOLLOWS ON NEXT PAGE
Name:
Partner:
Squad:
Fingerprinting Lab (Parts A-C)
Activity A – Fingerprint Classification (Loop – include radial or ulnar; Arch – include plain or tented;
Whorl – include plain, central pocket, double loop whorl or accidental)
Print: A -
J-
B-
K-
C-
L-
D-
M-
E-
N-
F-
O-
G-
P-
H-
Q-
I-
R-
Grade:
Activity B – Matching Crime Scene Fingerprints
Crime
Scene
Print #
1
2
3
4
5
6
Matching
Fingerprint
Letter
Crime
Scene
Print #
7
8
9
10
11
12
Matching
Fingerprint
Letter
Grade:
Crime
Scene
Print #
13
14
15
16
17
18
Matching
Fingerprint
Letter
Crime
Scene
Print #
19
20
21
22
23
24
Matching
Fingerprint
Letter
Activity C – Classifying your Own Fingerprints (include a Xerox of your 10 prints-attach below, so they can
be verified by your teacher; unreadable prints will be marked wrong; this is based upon the numerical
classification system). Note: the order of the fingers below is NOT the same as on the “10-Card”.
Grade:
R. Index
R. Ring
L. Thumb
L. Middle
L. Little
+ 1 = _____
R. Thumb
R. Middle
R. Little
L. Index
L. Ring
+ 1 = _____
1. Compare your numbers to others in your class (At least with the other members of your squad).
Does anyone else have the same numbers? Explain why or why not.
2. Are any of your ten fingers identical? How does your left hand compare to your right hand?
Explain.