Fingerprints are patterns on the skin formed early in development. There are three basic patterns: arches, loops, and whorls. Fingerprints can be patent, plastic, or latent. Latent prints require processing methods like powdering, chemical treatments, or alternative lighting to develop. Automated fingerprint identification systems and federal databases help law enforcement search large fingerprint collections to identify suspects or victims. Fingerprint evidence is collected and processed carefully, then analyzed and compared following established scientific standards.

1. What Fingerprints Are
• Fingerprints are patterns of friction ridge
skin
• Fingers and palms of hands, soles of feet
and are characterized by ridges (hills) and
valleys (furrows)
• Patterns form on skin surfaces early in
embryonic development and are carried
through life

3. Fingerprint Patterns
• There are three basic patterns of fingerprints:
• Arches – can be plain or tented
• Loops – radial or ulnar, depending on whether
direction of slope of pattern is towards inner arm
bone (radius) or outer arm bone (ulna)
• Whorls - most complex, and contain central
pocket, double loop, and accidental

7. Henry System
• Parts of the Henry System are:
–Key
–Major
–Primary
–Secondary
–Subsecondary
–Second Sub Secondary
–Final

10. Computer Based Fingerprint Files
• Automated Fingerprint Identification
Systems (AFIS) are used by law
enforcement
• This system searches databases for 10
point set of prints and searching large files
for single prints retrieved from a crime
scene

11. Law Enforcement Information
Systems
• FBI recently made its criminal database of
known fingerprint cards (IAFIS) available
• Latent print examiners can search
unknown latent impressions to assist in
identification of suspects or victims

12. Types of Evidentiary Fingerprints
• Three types of fingerprints
encountered at crime scenes or
on evidence:
–Patent
–Plastic
–Latent

13. Types of Evidentiary Fingerprints
• Patent – clearly recognizable fingerprint that
needs no processing – could be in grease,
blood, dirt, or oil
• Plastic print – also called an impression or
indentation print- could be in tar, butter, silly
putty
• Latent print – requires additional processing to
be rendered suitable for comparison –
processing is called development or
enhancement

14. Development of Latent Prints
• Fingerprint residue, which is composed of
inorganic and organic residues, comes
from eccrine glands and from touching
areas where apocrine glands in body are
before touching item
• Fingerprints can also come from touching
external sources- oils, tars, etc and then
touching surface of object

15. Physical Methods
• Latent fingerprint powder dusting is primary
method of visualizing fingerprints
• Black fingerprint powders generally have best
results
• Magnetic powders and brushes are now
available
• Small particle reagent (SPR) is sprayed on print
and adheres to lipids from prints

17. Chemical Methods
• Chemical methods of techniques for
visualizing fingerprints are:
–Silver nitrate – rarely used anymore
–Iodine fuming – very common –dirty
brown colored print and needs to
photographed quickly as it fades

18. Ambient Light

19. Silver Nitrate

20. Iodine-fumed

21. Chemical Methods
–Ninhydrin – used since 1910 and is slow
to react unless heat and humidity are
present – develops bluish-purple prints
–Cyanoracrylate (superglue) is used to
fume and yields an off white colored
print – use of heat and humidity
accelerates process

22. Ninhydrin

23. Cyanoacrylate
ester

24. Chemical Methods
• Physical Developer (PD) photographic
type process based on deposition of silver
onto latent fingerprint residue
• US Secret Service modified procedure and
uses colloidal gold to enhance prints
• Normally used after ninhydrin

25. Super glue
developed under
UV illumination
Treated
with ardrox
dye

26. Super glue
developed under
UV illumination
Treated with
Rhodamine-
6G

27. Combination and Special Lighting
• Various types of lights are used to
illuminate fingerprints
• Bright white light (525 nanometers),
lasers, and black lights with the use of
fluorescent powders are commonly used

28. Alternative
light source

29. Bloody Fingerprints and Other
Special Situations
• Bloody fingerprints normally are not latent
– primarily composed of blood
• Most processes for latent print chemical
enhancement do not interfere with blood
collection for DNA profiling by PCR for
CODIS
• Many bloody fingerprints are enhanced by
peroxidase- reaction chemicals

31. Bloody Fingerprints and Other
Special Situations
• Fingerprints that are on tape, especially
the sticky side, were developed by crystal
violet
• Most common method today is sticky side
powder, which is composed of lycopodium
(plant pollen) that is mixed with detergent
and water.

32. Recognition, Collection and
Preservation of Fingerprint
Evidence
• Fingerprints are among best evidence
• Objects at a crime scene which are believed to
contain prints should be collected
• If collection is impossible, latent development
techniques should be used
• Photographing of developed prints is advisable

33. Fingerprint Identification- The Heart
of the Matter
• David Ashbaugh (1999) noted fingerprint
individuality:
– Friction ridges develop in fetuses
– Friction ridges remain unchanged except for
scars
– Friction ridge patterns and details are unique
– Ridge patterns vary within certain boundaries
that allow patterns to be classified

34. Fingerprint Identification- The Heart
of the Matter
• Overall process of fingerprint examiner
according to Ashbaugh, A.C.E.V. :
–Analysis
–Comparison
–Evaluation
–Verification