L4-5: fingereprint identification Flashcards
describe volar pad formation [6-12 weeks fetus]
6 weeks
- hand is shaped like a paddle
- volar pads can be seen
8 weeks
- fingers separate
10 weeks
- digital pads are distinct
12 weeks
- friction ridges start to develop in basal layer of epidermis
- volar pads start to regress
4 premises of friction ridge skin
- friction ridges develop on the fetus in their definitive form prior to birth [embryology]
- friction ridges are persistent throughout life except for scarring, disease, or decomposition after death [histology]
- friction ridge paths and the details in the small area of the friction ridges are unique and never repeated [uniqueness]
- friction ridge patterns vary within limits therefore allowing for classification [classification, identification and exclusion]
another word for the bertillon system
bertillonage or anthropometry
describe the bertillon system
- alphonse bertillon [1853-1914]
- devised a method of personal identification through a series of body measurements
- full face and profile photographs of perpetrator now commonly known as mugshots in criminal cases
- head length and breadth, finger and foot measurements, eye and hair colour, weight, complexion, a single fingerprint
flaws with bertillon system
characteristics being measured are dynamic and can change, therefore are not 100% reliable
- young offender, not full grown
- repeat offenders, changing appearance and name
- human error in performing measurements
what did sir francis galton contribute to the history of fingerprint identification
- first to define and name specific minutiae known as ‘galton details’
- responsible for the acceptance of the use of fprints for personal identification
- suggested system of ID by means of a record of fprints only
what was the result of the troup committee when looking at the bertillon system and galton’s suggestion of fingerprint ID
- 1893
- bertillon system and fingerprintts were considered effective
- fprints did not have a classification system
- committee decided to implement both systems
5 major anthropometric measurements to be taken for primary classification, and fprints to be attaches as an additional component to the classification system
what did sir edward henry contribute to the history of fingerprint identification
- developed a classification system for fingerprints
- henry classification system
when/how did fingerprints as a means of identification become a standard practice in england [belper committee]
- belper committee [1900]
- recommended that all criminal ID records be classified by the fprint system
- the henry classification system and the individualization of criminals by means of fprints became a standard practice
describe 4 different volar pad development + fprint pattern configurations
- high & narrow vp –> whorl fp
- intermediate volar pad with steep radial side –> ulnar loop fp
- intermediate volar pad with steep ulnar side –> radial loop fp
- low & broad vp –> arch fp
factors that influence friction ridge skin formation
- shape and size of volar pad
- flow of the ridges follow the curvature lines of the skin on the volar pad - timing
- between the regression of the volar pads and the onset of the friction ridges - relative speed of the 3 developmental fronts
- genetics say that friction ridges must cover the entire surface
- develop at different speeds - genetics/diseases
- familial similarities
friction ridge skin characteristics
- referred to as volar skin
- seen in palmar and plantar surfaces
- seen in primates
- sweat glands only [no sebaceous glands]
- more sweat glands per square inch than other skin areas
- no hair
- lack of pigmentation
- each individual f.ridge unit has one sweat gland and one pore
- skin made up of 2 layers – dermis, epidermis
attributes:
- assists in ability to hold things [grip]
- provides traction to mitigate slippage
- sensory input [abundance of nerve endings]
- waste elimination through sweat glands
- thickness – must withstand daily gripping, lifting, touching, etc. [otherwise would be painful due to nerve endings]
2 layers in skin structure [L4:27…]
dermis
- thick foundation layer
- 15-40x thicker
epidermis
- cornified thin outer layer
- 15-20 layers of flat dead cells that are regularly shed through abrasion and replaced by regeneration
epidermis layers [young to old]
- basal layer
- spinous layer
- granular layer
- hyalin layer
- horny layer
[Basal’s Spinning Grandma is High [hy] and Horny]
describe the basal layer
- ‘generating layer’
- cells created in this layer migrate up towards the top layer
- cells typically flatten as they migrate to the top layers
- eventually once cells reach the top they slough off of dead skin cells
- cycle typically takes 30 days to complete
what are desmosomes
skin cells are connected through cell junctions called desmosomes
desmosomes release and reattach as needed during migration
what effects the persistency of friction ridge skin
injury, disease, and body decompostion
what happens when an injury damages or penetrates the basal layer
may destroy its ability to regenerate cells in that damaged area
surrounding cells can generate, but the deformation will result in the formation of a scar on the surface
what happens if an injury damages thee top layers of the epidermis
the skin will repair itself and friction ridge skin would gradually return to normal
how does body decomposition affect friction ridge skin persistence
- no new skin growth
- skin is less stable
- friction ridges simply degrade with the decomposition of the body
dyplasia effects on friction ridge persistency
- disease
- normal cells undergo abnormal changes
- may or may not be cancer
first level details of friction ridge skin
overall patterns
- loop
- whorl
- arch
describe loop patterns
- ridges flow in from one side, re-curve, flow out in the same direction
- a core and a delta
- common rating: 65%
what is an ulnar loop
- subcategory of a loop
- flow of ridges enter and exit towards the little finnger
