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1002 Fingerprints Cases.docx

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University of Toronto Mississauga
Forensic Science
Hisham Ragab

Introduction to Fingerprint examination Fingerprint Theory: Friction Ridge Skin The surface of the hands and feet (volar skin) are covered with a series of ridges and furrows which allows for friction (gripping) between any other surface they contact - Commonly referred to as “friction ridge formations - The ridges form unique patterns and arrangements‟allowing them to be used as a reliable means of identification Palms of Hands (Palmer) Soles of Feet Fingerprint Theory: Four Premises Friction Ridge Identification - Friction ridges develop on the fetus birth and remain during life and even following death, until decomposition of the ridge skin. They are unique at a result of the growth rate and random fusing of the ridge unite (differential growth) - Friction ridge are persistent throughout life except scarring/disease - Friction ridge pattern and the details of frictions ridges are never repeated. Despite millions of fingerprint and the advent of computer technology, no two fingerprint ever been found to be identical - The overall friction ridge pattern varies limits which for the classification of impressions Development Timeline for Friction Ridge Skin - Between 17-24 weeks  Ridge become visible spreading across fingers from  Fingertip  Apex of the volar pad  Distal flexion crease  Convergence of the 3 fields at delta area The Epidermis - All cells are generated by the Basal layer then migrate up - The PERMENECY of a fingerprint is as a result of this regeneration process Twin Study – Uniqueness After comparison of 3,920 fingers of twins, no two fingers were found to be the same What is a Friction Ridge? - Each friction ridge is made up of ridge units fusing together - Ridges have one of three things they can do - Join - Go around - Stop Ridgeology - Human Perception - You see with your MIND through your eyes Fingerprint pattern recognition - Arches - Loops - Whorls Loop - Loops  Comes in  Recurves  Goes back out same side  Usually curving around a delta Whorl - Whorl  1 core structure is present  Ridge recurves around 2 deltas  The deltas are found below the core Fingerprint Workflow - Ident officer examines an object (scene/lab) and develops friction ridge detail (commonly referred to as fingerprints/palm prints) through the use of but not limited to the following techniques:  Fingerprint powder – black/white/fluorescence  Cyanoacrylate (super blue fuming) and a dye stain applied and visualized with a forensic light source  Chemicals (used on paper documents) (The development medium used largely depends on the type of object i.e. porous vs. non-porous) Developing Chance Impression Latent (Invisible Impression) - Invisible to the naked eye - Most commonly encountered fingerprint - Requires some form of development – powder, chemical treatment, alternate light source to make it visible Patent (Visible Impression) - Composed of a combination of secretions and foreign materials (i.e. blood, grease, dirt etc.) and transferred from the finger to the surface - Visible to the naked eye, they require minimal development and must be photographed Plastic or Mold Impression 3 Dimensional impressions in soft material-example: - Chocolate - Cheese - Putty Deposit Impressions - The majority of fingerprint impressions found, they consist of material transferred from friction ridges to the surface of the item - May consist of bodily secretions or foreign material such as blood, oil paint, or dirt Digit Determination - When looking to examine a fingerprint the examiner should attempt to determine how the print was made - By doing this it helps to reduce the number of known prints searched Fingerprint Workflow - Friction Ridge Detail (Fingerprints) are then:  Photographed  Lifted, in the case of prints developed with powder, with the use of fingerprint tape and affixed to a piece of acetate - The photographs taken and the latent „lifts‟are retained indefinitely  Digital photos are saved onto a server  Lifts are stored in a Kardex style filing cabinet Fingerprint Workflow: AFIS Search - The photograph/life of the friction ridge detail (fingerprint impression) is submitted to theAFISAnalyst who searches the crime scene print against theAFIS database (Automated Fingerprint Identification System) in an attempt to identify the donor (candidate) - If theAFIS Analyst develops a „match‟onAFIS then the Ident Officer is given five different candidate fingerprint from one of which will be the donor that was found throughAFIS - The purpose of giving the Ident Officers multiple sets of fingerprint forms is to off-set alle
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