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Fingerprint Identification, Epidermis attached to dermis by double row of…
Fingerprint Identification
Fingerprint
refers to friction skin pattern formation found on human skin and the impression or mark left on surface after contact
Fingerprint Identification
impression or mark is a replication or transference of the patterned skin
friction skin has an accumulation of fingerprint secretions appearing on the raised area of a fingerprint impression, replication
Four Premises of Friction Ridge Identification
Overall, friction ridge patterns vary within limits, which allow for classification
Friction ridge paths and the details in small areas of friction ridges are unique and never repeated
Friction ridges are persistent throughout life except for permanent scarring, disease or decomposition after death
Friction ridges develop on the fetus in their definitive form prior to birth.
Use of fingerprints for personal identification in Canada back over 100 years
Anatomy
Friction skins = volar skin
Seen in Primates
Assists in ability to hold onto things or have traction
Prominent in the study of solar skin development were Whipple and Wilder
Characteristic of Volar surfaces
More sweat glands per square inch than other skin
No hair
sweat glands only
Lack of pigmentation
No sebaceous (oil) glands
Over-abundance of nerve-endings
Skin Structure
Ridge units grow and fuse together to form ridges
All grow the same time but at different rates
FRICTION RIDGE FORMATION & DIFFERENTIAL GROWTH RATE
Genetics - familial similarities
Physical forces - pressure, tension and disease
12 WEEKS, Primary friction ridges and patterns start to develop.
All primary ridges grow for the same amount of time, but differential growth rate is key to random development
Ridges made up ridge units. 1 unit = 1 sweat gland and one pore
2 layers
Dermis
thick foundation layer
Epidermis
thing outer later of 15-20 layers of dead cells that are replaced continuously from the basal layer between these layers
Layers of Epidermis
Stratum granulouum (granular)
Stratum spinous (spinous)
Stratum lucid (hyalin/hyaline)
Stratum basal/basale (basal)
basal is referred to generating layer
epidermal cell rejuvenation occurs
Cells created will migrate upward towards other four layers to the surface where they become dead skin cells (1 month)
Stratum corner (horny)
Fingerprint Composition
3 sources of secretion:
Sebaceous glands
apocrine glands
Eccrine glands
Apocrine sweat is found in the underarm and genitals so its not a consideration
Fingerprint deposit is a combination from different sources
Eccrine sweat glands
located over the entire body
located on the palmar and plantar surfaces
secreted by sweat pores located along the peak areas of friction ridge skin
Sebaceous glands
found on areas of the body with hair follicles
Sebum is secreted
composed of saturated fats, waxes and squalene
Sebum migrates as we touch areas of our body where it is secreted
Fingerprint Identification
Finger identification is established through the continuous agreement of friction formations, in sequence having sufficient uniqueness too individualize
Focal points
Core: the central area.
Delta: triangle-shaped area of a fingerprint where the ridge formation changes direction
Basic Fingerprint Patterns
Loop (60%)
One or more friction ridges enter on side, recurve/touch/pass an imaginary line between delta and core, and flow out on the same side
Whorl (30%)
ridges that make a complete circuit with two deltas, at least one recurving ridge within the inner pattern is cut or touched
Arch (10%)
one or more frictions enter on one side of the impression and flow out the other side with a rise/wave in the centre
Level 1 characteristics
Focal Points
Core, Deltas, Scars Creases
Pattern Type
Identifications cannot occur at this level of information
Overall ridge flow
Level 2 Characteristics
Individual ridge paths/events
Bifurcations
Dots
Ending ridges
Islands
2nd level: Minutiae
Level 3 Characteristics
Size and shape of pores and ridges
Pores
Edge shapes
End shapes and angles
Width
Identification and exclusion decisions can be supported at this level of information
3rd level: Friction ridge dimensional attributes
Levels of Characteristics Summary
Second level - Galton
Need magnifying glass
ridge characteristics (ridge endings, bifurcations, islands, lakes) - mutineer or galton details
primary source of individualization
Third level - Ashbaugh
microscopic
location of pores in ridges, shapes of edges of ridges (how ridges affect each other)
useful if there is insufficient 2nd level detail
First Level - Henry
Visible to naked eye
ridge flow and pattern, core, delta, useful to give indication of where to look (can be misleading due to distortion)
Friction Ridge Identification
Exclusion
The determination by an examiner that there is sufficient
quality and quantity of detail in disagreement to conclude
that two areas of friction ridge impressions did not originate
from the same source. source.
Inconclusive
During Evaluation, the conclusion reached that neither
sufficient agreement exists to individualize nor sufficient
disagreement exists to exclude. exclude.”
Identification
The determination of an examiner that there is sufficient
quality and quantity of detail in agreement to conclude that
two friction ridge impressions originated from the same
source.source
Epidermis attached to dermis by double row of dermal papillae
