WVU FIS 201 Exam 3 Study Questions and Answers Graded A 100% Verified 2024

anatomy of fingerprints - friction ridges when do volar pads start forming? - 4 months what is unique about volar pads? - consistent throughout life 3 steps of creating an impression - - sebrum & sweat - spreads along ridge surface - sticks to substrate when pressed foreign materials that could potentially have fingerprints - - blood, ink, motor oil, pizza grease 3 types of prints - patent, latent, impression/plastic patent - see without additional assistance latent - hidden fingerprint impression/plastic - occur when soft surface is deformed 2 ways to collect known prints - - voluntary submission - prints are taken at booking (live scan, rolled ink) what print is naked to the eye? - latent print what print must be developed with chemicals or light? - latent print porous - immediately absorb water nonporous - do not absorb water semiporous substrates - can absorb water over time what substrates should dusting be used on? - nonporous & semiporous how does dusting work? - powder adheres to fats & oils how to dust evidence? - gently apply with fiberglass or magnetic brush locations to look for fingerprints - door frames & handles, windows, furniture, appliances how to lift a print - 1. photograph 2. press the lifting tape across the print 3. smooth the tape flat 4. lift off the print 5. press it over the lift card what substrates should ninhydrin be used on? - porous substrates what does ninhydrin react to? - reacts with amino acids in print to form Ruhemann's Purple what does ninhydrin also work with? - faint prints in blood what substrate is cyanoacrylate fuming used on? - nonporous how does cyanoacrylate fuming work? - binds to fats in the presence of water and forms a protective layer over ridges what is cyanoacrylate fuming useful for? - degraded or fragile prints how to collect a fingerprint on a bright colored background? - cyanoacrylate fuming first, fluorescent dye or dust eliminates background and they can only be "lifted" via photograph gentian violet - dye, works well on clear tape sticky side & wet wop - powder suspended in detergent, color allows max contrast 3 ways to collect fingerprints on adhesive surfaces - gentian violet, sticky side & wet wop, photograph textured surfaces - frequently touched surface, texture allows for easy grip how to collect fingerprints on textured surfaces? - dust first then lift with a squishy material squishy materials to lift with - - mikrosil/polyvinylsiloxane - Diff-Lift Diff-Lift - thick, squashy tape leucocrystal violet - reacts with hemoglobin, works on porous & nonporous substrates