lecture 3 - fingerprints

Question 1

importance of fingerprints

Answer 1

• useful as they are unique to each individual
• do not change during a person’s lifetime

Question 2

what are fingerprints

Answer 2

• deposition of friction ridges
• appear on palms, soles, and end of fingers and toes

Question 3

features of fingerprints

Answer 3

• ridge = single curved segment
• furrow = legion between 2 adjacent rings
• pore = found on ridges for respiration

Question 4

visible fingerprints

Answer 4

• made by fingers touching a surface after the ridges have been in contact with a coloured material (blood, paint, ink, etc.)

Question 5

patent and plastic fingerprints

Answer 5

• patent = meaning obvious or evident and occurs when fingers are contaminated with something
• plastic - made when finger touches or presses against a soft-pliable surface

Question 6

latent fingerprints

Answer 6

• once the finger touches a surface, body perspiration and/or oil present on finger ridges are transferred to surface leaving an impression
• invisible to the eye

Question 7

how long do fingerprints last

Answer 7

• plastic prints remain as long as impressed material is structurally intact
• prints left in blood/dust are fragile and do not last long
• latent prints in proper environment can last for years

Question 8

parameters on how well a fingerprint is formed

Answer 8

• surface
• pressure applied
• time for which pressure is applied

Question 9

fingerprint patterns - several types of whorls

Answer 9

• plain
• central pocket
• double loop
• accidental

Question 10

loops and whorls contain:

Answer 10

• cores and deltas

Question 11

core

Answer 11

• approx. centre of fingerprint
• area of max curvature

Question 12

deltas

Answer 12

• point on a ridge where there is a triangulation or point of divergence

Question 13

minutiae (individual)

Answer 13

• means fine detail
• fingerprint minutiae used to individualize them
• individual ridge characteristics
  – ~150 on average print
  – 8-16 matching are sufficient for identification

Question 14

unusual fingerprints

Answer 14

• skin disease
• genetic disease
• scars

Question 15

procedure for developing latent prints

Answer 15

• visual examination
• photography
• illumination methods
• chemical fuming or powder dusting

Question 16

illumination techniques

Answer 16

• oblique lighting
• expose fingerprint to UV or laser light
• usually done after application of dye

Question 17

enhancement techniques

Answer 17

• used to increase contrast between mark and backdrop
• contrast may be colour or brightness
• techniques work by adding “label” to some compounds found in fingerprint
• can use number of enhancement techniques

Question 18

powder dusting

Answer 18

• simplest method
• adherences of powder particles to sweat components of friction ridge deposits

Question 19

powder dusting - brushes

Answer 19

• applied with soft fibreglass brush that has long fine bristles
• do not make contact with surface

Question 20

chemical enhancement

Answer 20

• method of visualizing prints from recovered objects
• not conducted at the crime scene
• involves exposing objects to fumes

Question 21

fingerprint matching step 1 - fingerprint to class

Answer 21

• loop
• arch
• whorl

Question 22

fingerprint matching step 2 - minutiae

Answer 22

• position
• type
• number
• orientation

Question 23

fingerprint ridge analysis

Answer 23

• friction ridges are studied for the kind, number and location of various ridge characteristics or minutiae
• arrangement of characteristics creates one of a kind pattern
• point counting standard dictates how many points of comparison were required before positive conclusion could be reached

Question 24

AFI - automated fingerprinting identification system

Answer 24

• 1960s
• computerized fingerprint search and storage system
• search for reference/inked prints
• places two images side by side and allows examiner to chart common features on both images simultaneously