1. FINGERPRINTS
COLLEGE FORENSICS

2. WHAT ARE FINGERPRINTS???
A fingerprint is an impression of the friction ridges found on the inner surface of a finger or a thumb

3. Cross-Section of
Friction Skin
*Subcutaneous (hypodermis)
-Lowest layer
*Dermis – Middle layer
-protein
*Epidermis – Outer layer
An injury must penetrate the dermal layer to alter a print.

4. 1)  Ridge patterns and the details in small areas of friction ridges are unique and never repeated.
2)  Friction ridges develop on the fetus between the 3rd and 5th month of prenatal development. The dermal papillae determines the pattern.
*Ridges are persistent throughout life except
for permanent scarring.
3)  Friction ridges increase the surface area of the fingertip and hands to assist in gripping items.

5. RIDGES & FURROWS
Ridges – top of the ‘hill’
Furrows – Lower ‘valleys’

6. FINGERPRINT PATTERNS: Arch
Tented Arch: Smaller angle at top of arch
*Ridges enter & exit from opposite sides.
*Found on approx. 5% of the population
*No deltas, no core
Plain Arch

7. FINGERPRINT PATTERNS: Loop
*Ridge enters & exits from the same side
*Found in 60-70% of the population
*1 Delta (point where 3 ridges converge) & 1 Core
*Loops are classified as radial or ulna, depending on which direction it opens towards.

8. Direction changes with right vs. left hand

9. FINGERPRINT PATTERNS: Whorl
*Completes a 360o pattern
*Found in 25-30% of population
*2 Deltas, 1 Core
*Many forms of whorls:
-Plain whorl 
-Central pocket
-Double loop
-Accidental

10. FINGERPRINT PATTERNS: Whorls
Central Pocket Loop
Double Loop
Accidental

11. Levels of Detail
What are the three levels of detail in a fingerprint???
Structure (type of pattern)
Individual minutae/friction pattern
Detail of ridge measurement (width, length, distance between minutae)

12. FINGERPRINT MINUTIAE
WHAT MAKES ONE PERSON’S FINGERPRINT DIFFERENT FROM ANOTHER PERSON’S?
There are small patterns and designs that are present on the ridge pattern of your fingertips. These small differences make fingerprints unique.

13. TYPES OF MINUTIAE
Dot:
Bifurcation:
Trifurcation:
Lake/
Enclosure:

14. Minutae Ridge Ending: Island/Short Ridge:
*A short ridge doesn’t travel through the entire pattern; It is only a few millimeters in real size.

15. Minutae
Break:
Hook:
Bridge:
Island:

16. Let’s Look at this print…

17. MINUTIAE TYPE OF PATTERN: Arch UNIQUE CHARACTERISTICS: *Lake
*Bifurcation
*Island
*Ridge Ending
*Break

18. RIDGE COUNT
The number of ridges crossed between a delta and the core of the pattern.
*Can only be done on loops & whorls.
*Whorls will have a
right ridge count
& a left ridge count.

19. Primary Classification
A numerical system of classifying a full set of prints based on the whorl pattern.
*Numerical values are assigned to each finger
*If the finger has a whorl pattern, then plug that number into the primary classification equation.
*If a whorl is not present, use ‘0’ as that finger’s value
*Final classification is NOT reduced & left in the fraction form.

20. PRIMARY CLASSIFICATION (Henry Classification System)
NUMBERS ASSIGNED IF A WHORL IS PRESENT:
Fingers #1,2 = 16 Fingers #3,4 = 8
Fingers #5,6 = 4 Fingers #7,8 = 2
Fingers # 9,10 = 1
EQUATION =
(Sum of #’s assigned to even numbered fingers) +1
(Sum of #’s assigned to odd numbered fingers) +1
*Practice Problems

21. PRIMARY CLASSIFICATION (Henry Classification System)
Therefore, a person with whorl patterns on all of their fingers would have a Primary Classification of 32 32
And a person with no whorl patterns on any of their fingers would have a Primary Classification of 1 1
These ratios are not to be reduced, they are to be left as calculated.

22. SECONDARY CLASSIFICATION
Fraction of index finger patterns:
Right Index Pattern
Left Index Pattern
Patterns: Arch = A Tented Arch = T
Ulna L. = U Radial L. = R
Whorl = W (any whorl pattern)
Example: A/T (right index has an arch, left
index has a tented arch)

23. DEVELOPING FINGERPRINTS
Types of fingerprints:
1)Latent – Impressions caused by oils, water, amino acids (perspiration) left on a surface
2)Visible Prints – Left when ridges have a colored/medium substance on them
3)Impression Prints – ‘Plastic’ prints left in a soft material

24. DEVELOPING FINGERPRINTS
DEVLOPING FINGERPRINTS DEPENDS ON…
1) SURFACE THE PRINT IS ON
*Porous (Absorbent)
*Non-porous (nonabsorbent)
2) METHODS FOUND SUCCESSFUL BY DEVELOPER

25. DEVELOPING FINGERPRINTS: Nonabsorbent surfaces
1) Powder –
Adheres to body oils, perspiration.
-Color used depends on
background.
-Lift with tape, place on card.
Print card contains information
of the suspect (name, DOB,
age, height, weight)

26. DEVELOPING FINGERPRINTS: Nonabsorbent surfaces
Developing Latent Prints on
Nonabsorbent Surfaces
2) Reflected UV Imagining System (RUVIS)
- UV light strikes print and
reflects back to a viewer
that is converts it to visible
light.

27. DEVELOPING FINGERPRINTS: Nonabsorbent surfaces
3) Superglue Fuming – Fumes react with amino acids and make it white.
-Cyanoacrylate ester is the chemical
that interacts with the print.
-Superglue is heated to
produce a vapor.
-Can be used on small
objects or cover a large
area (car interior)

28. DEVELOPING FINGERPRINTS: Absorbent surfaces
1) Iodine Fuming – Iodine fumes combine with fatty oils / water
-Iodine sublimes (solid  gas)
-Not a permanent image

29. DEVELOPING FINGERPRINTS: Absorbent surfaces
2) Ninhydrin – Chemical treatment; reacts with amino acids in perspiration.
-Sprayed onto surface; 1-2 hours to develop.
-Produces purple-blue print
-Last for hours

30. DEVELOPING FINGERPRINTS: Absorbent surfaces
3) Silver-nitrate (Physical developer) –
Solution reacts with chloride ions in sweat but washes away any trace of protein left on print.
-Last resort for
developers
- May detect prints on
porous objects that
may have been wet
@ one point.

31. Order of Chemical Treatments
Since some chemical treatments are more destructive than others, the treatments must be performed in the following order…
1) Iodine fuming
2) Ninhydrin
3) Silver nitrate

32. VISUALIZING FINGERPRINTS
*Alternate Light Source (ALS) – Specific wavelengths of light aimed at a print; Based off of fluorescent tendencies of chemically treated prints.
(Previously done with lasers)
-Cheaper than lasers
-Portable, easy to use
-Used with chemical treatments

33. DEVELOPING FINGERPRINTS

34. PRESERVATION OF PRINTS
After visualization, prints must be permanently preserved
At Crime Scene photograph first (Close-up of print and relationship to evidence)
Object collected or print lifted from large objects.
*Prints are lifted by placing cellophane tape over a dusted print.

35. PRESERVATION OF PRINTS
DIGITAL IMAGING – Computer programs used to enhance photos of prints
*Filters used to make print clearer
(Grayscale, contrast, interference)
*Colors can be differentiated (print on
a dollar bill or colored background)
*’Compare’ function – side-by-side
comparison.

36. The End