Fingerprint Identification Part 2 Flashcards
What are the two possible sources of a fingerprint deposit?
Natural secretions
Foreign materials
What are the two types of natural secretions that can cause a fingerprint deposit?
Eccrine (sweat)
Sebaceous glands
Where are eccrine glands found?
All over the body but in greatest density on hands and feet
What controls eccrine glands?
Autonomic nervous system
What type of stimuli do eccrine glands respond to?
Thermal, emotional or medical
What is the composition of eccrine glands?
98.5 to 99.5% water
1.5 to 0.5 % solids
What are the main constituents of sebaceous gland secretions?
Saturated fats, waxes, squalene
Are sebaceous glands naturally occurring on the hands?
No, but secretions can end up there as a result of a migration process
Give examples of foreign materials that can produce fingerprints.
Paint
Automotive lubricants
Dirt
Dust
Industrial grease
Oil
Cooking or food residue
Blood
What are the 5 factors that impact fingerprint composition?
Rate and duration of sweating
Dietary habits
Age
Physical health and exertion
Stress level
How does rate and duration of sweating impact fingerprint composition?
Excessive and prolonged sweating can dilute the concentration of solids within the sweat.
How do dietary habits impact fingerprint composition?
Certain food intake or lack thereof (e.g., salts, fats) influence secretion content. Fluctuates within the individual as well as person to person.
How does age impact fingerprint composition?
Concentrations and components within the sweat tends to lessen as we get older.
How can physical health and exertion impact fingerprint composition?
Physical health or fitness activities may influence the quantity of sweat therefore relating back to the rate and duration of sweating.
How can stress level impact fingerprint composition?
Elevated stress or anxiety levels has been shown to cause a higher concentration of solids in sweat.
Differs from person to person
Why is stress level particularly important in terms of crime and fingerprints?
If someone is making the conscious decision to commit a crime, or actively engaged in the commission of an offence, stress and anxiety levels often increase, resulting in more sweating.
Differentiate between the life span and age of a fingerprint.
Life span - theoretically how long a fingerprint can survive on a surface
Age - when was the fingerprint deposited?
What is the life span of a fingerprint dependent on?
Composition of the impression (the person)
The surface
The environment
How do we gauge the potential lifespan of a fingerprint?
There is currently no known way to accurately gauge this information
How do freezing temperatures impact fingerprints?
Solidify secretions
Powder adheres to background and fingerprint equally, thus no visible difference
How does hot sunny weather impact fingerprints?
Causes secretions to bake on the surface as the moisture is quickly evaporated.
How does high humidity impact fingerprints?
Powder adheres to everything and tends to smear the fingerprint impression and results in contaminating your brush.
How can we determine the age of a fingerprint?
POS receipt (time stamped)
Witnesses
CCTV and video recording
What is the general rule regarding the suitability of surfaces for fingerprints?
Fingerprints may be found on any surface with sufficient size and surface continuity to disclose the necessary ridge characteristics in sequence.
What are the four factors of surface suitability?
Size
Surface continuity
Material
Surface cleanliness
How does surface continuity impact surface suitability?
Smoothness of an object is a limiting factor in disclosing ridge detail.
How does material impact the suitability of a surface?
Dictates which development technique is used
How does surface cleanliness impact surface suitability?
Weigh out the pros/cons of brush contamination, possibility of a take away impression
