FINGERPRINTS COLLEGE FORENSICS WHAT ARE FINGERPRINTS A fingerprint

FINGERPRINTS COLLEGE FORENSICS

WHAT ARE FINGERPRINTS? ? ? A fingerprint is an impression of the friction ridges found on the inner surface of a finger or a thumb

1) Ridge patterns and the details in small areas of friction ridges are unique and never repeated. 2) Friction ridges develop on the fetus in their definitive form before birth. 3) Ridges are persistent throughout life except for permanent scarring. 4) Friction ridge patterns vary within limits which allow for classification.

Cross. Section of Friction Skin Epidermis Papillae Dermis

FINGERPRINT PATTERNS ARCH *LINE ENTERS & EXITS PATTERN AT DIFFERENT SIDES *NO DELTAS

FINGERPRINT PATTERNS TENTED ARCH *LINE ENTERS & EXITS PATTERN AT DIFFERENT SIDES *NO DELTAS

FINGERPRINT PATTERNS LOOP *ENTERS & EXITS FROM SAME SIDE *1 DELTA

Ridge Count: # of ridges between tip of core and tip of delta

Ulna and Radial Loops l Are hand dependent l l Ulnar loop - the loop opens toward the little finger. Radial loop - the loop opens toward the thumb R Left Hand U U R Right Hand

FINGERPRINT PATTERNS WHORL *’SPIRAL’ PATTERN *2 DELTALS *MANY FORMS OF WHORLS

FINGERPRINT PATTERNS DOUBLE LOOP *2 LOOPS INTERTWINED *2 DELTAS

FINGERPRINT PATTERNS CENTRAL POCKET LOOP *’EYE’ PATTERN IN CENTER OF THE PATTERN *2 DELTAS

More Whorls

FINGERPRINT MINUTIAE WHAT MAKES ONE PERSON’S FINGERPRINT DIFFERENT FROM ANOTHER PERSON’S? There are small patterns and designs that are present on the ridge pattern of your fingertips. These small differences make fingerprints unique.

TYPES OF MINUTIAE Dot: Bifurcation/Fork: Trifurcation: Lake/Enclosure:

TYPES OF MINUTIAE Ridge Ending: Island: Short Ridge

TYPES OF MINUTIAE Break/Gap: Bridge: Hook:

Let’s Look at this print…

MINUTIAE TYPE OF PATTERN: Arch UNIQUE CHARACTERISTICS: *Lake *Bifurcation *Island *Ridge Ending *Break *Hook

PRIMARY CLASSIFICATION (Henry Classification System) Classification system based on the WHORL pattern 1)Determine whorl patterns on set of prints 2)Assign given numbers to these fingers 3)Plug in assigned values into equations

PRIMARY CLASSIFICATION (Henry Classification System) NUMBERS ASSIGNED: Fingers #1, 2 = 16 Fingers #3, 4 = 8 Fingers #5, 6 = 4 Fingers #7, 8 = 2 Fingers # 9, 10 = 1 EQUATION = (#’s assigned to even numbered fingers) +1 (#’s assigned to odd numbered fingers) +1

PRIMARY CLASSIFICATION (Henry Classification System) Therefore, a person with whorl patterns on all of their fingers would have a Primary Classification of 32 32 And a person with no whorl patterns on any of their fingers would have a Primary Classification of 1 1 These ratios are not to be reduced, they are to be left as calculated.

SECONDARY CLASSIFICATION ‘Ratio’ of index finger patterns: Right Index Pattern Left Index Patterns: Arch = A Tented Arch = T Ulna L. = U Radial L. = R Whorl = W (any whorl pattern)

DEVELOPING FINGERPRINTS Three types of fingerprints @ a crime scene: 1)Latent – Impressions caused by perspiration / oils on ridges (not seen easily) *Visualization depends on surface*

DEVELOPING FINGERPRINTS 2)Visible Prints – Left when ridges have a colored substance on them (blood, ink/paint, etc. ) 3)Plastic Prints – Impression left in a soft material (clay, drying blood) *Easy to find at a crime scene*

DEVELOPING FINGERPRINTS METHOD OF DEVLOPING FINGERPRINTS DEPENDS ON … *SURFACE THE PRINT IS ON *METHODS FOUND SUCCESSFUL BY DEVELOPER

DEVELOPING FINGERPRINTS Developing Latent Prints on Nonabsorbent Surfaces *Powder – Adheres to body oils & perspiration. -Usually grey, black powders; Other colors used depending on background. -Lifted with tape, placed on card.

DEVELOPING FINGERPRINTS

DEVELOPING FINGERPRINTS *Superglue Fuming – Fumes adhere to the print and make it white. -Cyanoacrylate ester is the chemical that interacts with print -Superglue is heated to produce fume -Has worked on the interior of a car

DEVELOPING FINGERPRINTS

DEVELOPING FINGERPRINTS *Reflected UV Imagining System (RUVIS) - UV light strikes print and reflects back to a viewer that is converts it to visible light.

DEVELOPING FINGERPRINTS Developing latent fingerprints on Absorbent Surfaces *Iodine Fuming – Iodine fumes combine with fatty oils / water -Iodine sublimes (solid gas) -Not a permanent image

DEVELOPING FINGERPRINTS

DEVELOPING FINGERPRINTS *Ninhydrin – Chemical treatment that reacts with amino acids in perspiration. -Sprayed onto surface -Produces purple-blue print -Takes 1 -2 hours to develop (heat increases rate) & last for 24 -48 hours

DEVELOPING FINGERPRINTS

DEVELOPING FINGERPRINTS *Silver-nitrate (Physical developer) – Solution reacts with print but washed away any traces of protein left on print -Last resort for developers

DEVELOPING FINGERPRINTS

DEVELOPING FINGERPRINTS *Alternate Light Source (ALS) – Specific wavelength of light used to illuminate fingerprint. -Portable, easy to use -Used with chemical treatments

DEVELOPING FINGERPRINTS

PRESERVATION OF PRINTS After visualization, prints must be permanently preserved At Crime Scene photograph first (Closeup of print and relationship to evidence) Object collected or print lifted from large objects.

PRESERVATION OF PRINTS DUSTING & LIFTING PRINTS *Lightly dust in direction of ridge pattern *Place lifting tape over print *Peal off and place on labeled card with a color that contrasts powder

PRESERVATION OF PRINTS DIGITAL IMAGING – Computer programs used to enhance photos of prints *Filters used to make print clearer (Grayscale, contrast, interference) *Colors can be differentiated (print on a dollar bill or colored background) *’Compare’ function – side-by-side comparison.

AFIS Digital mapping of fingerprint

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