What ensures the persistency of friction ridges?
- the connection of the basal cells to the basement membrane (basal lamina) by hemi-desmosomes which prevent the basal cells from migrating upwards
- dermal papillae which help anchor the epidermal layer to the dermis
- desmosomes which hold the cells together as the migrate upwards
What four (4) factors contribute to the “uniqueness” of fingerprints?
- shape, location and symmetry of the volar pads
- random areas of growth of the primary and secondary ridges
- random timing of growth of the primary and secondary ridges
- random pressures the volar areas are exposed to during primary and secondary ridge growth (pressures in womb, pressures of neighbouring ridges)
What is the methodology used for friction ridge identification?
ACE-V
- Analysis, Comparison, Evaluation, Verification
What is the purpose of the “analysis” stage in ACE-V?
It is the breaking down of an impression into various components, gathering of all available information in an impression, determining the level of tolerance for discrepancies and the overall suitability of the impression for comparison purposes.
Who coined the term, “Ridgeology”?
- retired S/Sgt. David Ashbaugh of the RCMP
What are the sciences involved in “Ridgeology”?
Biology Histology Embryology Dermatoglyphics Genetics
What is the philosophy of friction ridge identification?
Friction ridge identification is established through the agreement of friction ridge formations, in sequence, having sufficient uniqueness to identify.
What are the four premises of friction ridge identification?
- friction ridges develop on the fetus in their definitive form before birth
- friction ridges are persistent throughout life except through injury
- friction ridges and small details within those ridges are unique and never repeated
- overall friction ridge formations vary within limits and allow for classification
What are the two types of skin?
Volar (covered in friction ridges, only create sweat, do not produce oil, no hair)
Smooth (no friction ridges, create sweat and oil, have hair)
What are the five (5) layers of the epidermis from top to bottom?
Horny, Hyalin, Granular, Spinous, Basal
Why is the epidermis decided into five different layers?
- they are named based on microscopic appearance of the keratinocytes
- the keratinocytes change in appearance and composition as they migrate upwards
- during migration the cells become keratinized
What are the effects of age on the friction skin?
- surface ridges tend to flatten, making them appear less sharp
- loss of elasticity in the dermis causes the the skin to become flaccid and wrinkle
What type of injury would cause a scar?
- injury to the basal layer, which causes the dermis to contract, shortening the distance that the epidermal keratinocytes need to travel to cover the wound bed
What are, “Volar Pads”?
- swelling of mesenchyme tissue under the epidermis on the volar surfaces of the hands and feet
What is meant by, Volar Pad Regression”?
- volar pad regression occurs around approximately week 10.5-12
- volar pads aren’t actually regressing, but are being taken over by the faster growing surrounding surface, making them appear less distinct
What affects pattern type?
- the size, shape and symmetry of the volar pad at the onset of primary ridge formation
What are the three main fingerprint pattern types?
- loops
- arches
- whorls
What fingerprint pattern is most common?
Loops
What are the two types of impression recorded on C216 forms?
- plain
- rolled
What are the three types of fingerprints found at a crime scene?
- visible
- latent
- molded
Are two friction ridge impression of the same finger ever exactly alike? If not, why?
No, each independent deposit of an impression does not produce a perfect replication of a previously deposited one. There are always variations in appearance due to factors such as:
- distortion
- matrix
- substrate
- over/under inking
What two (2) fundamental principles must be understood by an examiner prior to reaching a conclusion from the examination process?
- uniqueness and persistency of the friction skin
What are the three (3) conclusions that can be reached following the evaluation stage of friction ridge skin?
- Identification
- Inconclusive
- Exclusion
