Forensic science exam 2

what are fingerprints

the friction ridge skin of the last joint on each finger taken from cuticle to cuticle

the ridges come from the skin, specifically the ______ _______ layer which is between the epidermis and dermis

dermal papillae

ridges begin forming in the womb at ~8 weeks gestation and are fully formed by __ weeks gestation

17

Do identical twins have the same fingerprints?

no

3 major fingerprint patters

arch, loop, whorl

arches have __ deltas

0

loops have _____ delta(s)

1

whorls have ____ deltas

2

two types of arches

plain and tented

Two types of loops

radial (towards thumb) and ulnar (towards pinkie)

4 types of whorls

Plain, central pocket loop, double loop, accidental

Minutiae patterns

-Ending ridge (straight ridge)

-Bifurcation (Fork)

-Dot (literally a solid dot)

-Trifurcation (forked into 3)

-Enclosure (oval)

-Short ridge (segment of ridge)

fingerprints replaced what system

Bertillion system

Father of Fingerprints

Sir Francis Galton

3 types of prints on a surface

latent print, patent print, plastic print

latent print

typically invisible print deposited when perspiration residue along with sweat, skin cells, proteins, fats and other materials are left behind when a finger touches a surface

Patent print

readily visible and typically deposited in paint or blood

plastic print

print formed in a self material such as putty

3 fundamental fingerprint principles

1. fingerprint is an individual characteristic

2. remains unchanged during a person's life

3. have general ridge patterns that allow them to be systematically classified

fingerprints are widely used for identification because they are both _____ and ______

unique and persistent

surface characteristics

porous, nonporous smooth, nonporous rough, special conditions, wet or dry

a crime scene is the ______ place to collect fingerprints

worst (better to submit the entire item for processing in the lab)

before lifting a print you must

photograph with a scale

visualization of latent prints

-powders (on non-porous surfaces)

-RUVIS (reflected ultraviolet imaging system also used on non-porous surfaces)

-iodine fuming (oldest method)

-ninhydrin (porous surfaces)

-physical developer (porous surfaces)

-superglue fuming

powered and brush techniques

light touch, swirling motion

fingerprint photographs

need scale, sensor parallel, best done with tripod

labeling print index card

front: small image of item collected from and where the print was on item, directionality (which direction was the print facing)

back: case #, person collecting, collection date and time

fingerprint ACE-V method

analysis, comparison, evaluation, verification

loop, whorl, arches, is

class characteristics

ridge characteristic and minutiae is

individual characteristics

AFIS (automated fingerprint identification systems) does ____ make a match and examiner must do this

NOT

the American court system is based on the

English common law system

Frye vs. United States (1923)

Under the "Frye Standard" a court has to decide if the procedure, technique or principles in question were generally accepted by a meaningful proportion of the relevant scientific community.

Federal Rules of Evidence (FRE)

Rules established by the US Supreme Court guiding the introduction and use of evidence in federal court proceedings. We are concerned with opinions and expert testimony (rule 702)

what is the main job of the expert witness

to educate the jury

Daubert V Merell Dow Pharmaceuticals Inc case

created 5 prongs as a test for admissibility

5 prongs of Daubert

-whether the theory or technique in question can be or has been tested

-whether it has been subjected to peer review and publication

-its known or potential error rate

-the existence and maintenance of standards controlling its operation

-whether it is widely accepted in the relevant scientific community

General Electric Co V. Joiner

the standard or review for this inquiry is the abuse of discretion standard

Kumho Tire Co. v. Carmichael

it applies Daubert to expert testimony from non-scientists

Brady v. Maryland

"that casts the prosecutor in the role of an architect of a proceeding that does not comport with standards of justice"

spatter is defined as

to scatter or dash in small particles or drops

blood drops hold together in free flight through the forces of _____ and ______ _______

cohesion and surface tension

Blood falls as a...

sphere

bloodstain

deposit of blood on a surface

bloodstain pattern

A grouping or distribution of bloodstains that indicates through regular or repetitive form, order, or arrangement the manner in which the pattern was deposited.

target

surface onto which blood has been deposited

parent stain

A bloodstain from which a satellite stain originated.

satellite stain

A smaller bloodstain that originated during the formation of the parent stain as a result of blood impacting a surface.

directionality

The characteristic of a bloodstain that indicates the direction blood was moving at the time of deposition.

directionality angle

the angle between the long axis of a spatter stain and a defined reference line on the target

angle of impact

The acute angle, relative to the place of a target, at which a blood drop strikes the target.

area of convergence

The space in two dimensions to which the directionalities of spatter stains can be retraced to determine the location of the spatter producing event.

area of origin

the space in three dimensions to which the trajectories of spatter can be utilized to determine the location of the spatter producing event

Accompanying Drop

A small blood drop produced as a by-product of drop formation.

altered stain

A bloodstain with characteristics that indicate a physical change has occurred.

perimeter stain

An altered stain consisting of its edge characteristics, the central area having been partially or entirely removed.

wipe pattern

an altered stain resulting from an object moving through a preexisting wet bloodstain

back spatter pattern

a bloodstain pattern resulting from blood drops that can be produced when a projectile creates an entrance wound

forward spatter pattern

a bloodstain pattern resulting from blood drops that can be produced when a projectile creates an exit wound

bubble ring

An outline within a bloodstain resulting from air in the blood.

cast-off pattern

A bloodstain pattern resulting from blood drops released from an object due to its motion.

how to determine # of strikes?

count the arcs +1= minimum # of blows

cessation cast-off pattern

A bloodstain pattern resulting from blood drops released from an object due to its abrupt deceleration.

drip stain

A bloodstain resulting from a falling drop that formed due to gravity.

drip pattern

A bloodstain pattern resulting from a liquid that dripped into another liquid, at least one of which was blood.

drip trail

A bloodstain pattern resulting from the movement of a source of drip stains between two points.

Edge characteristics

A physical feature of the periphery of a bloodstain.

spines

The pointed or elongated stains which radiate away from the central area of a bloodstain.

expiration pattern

A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or a wound.

flow pattern

A bloodstain pattern resulting from the movement of a volume of blood on a surface due to gravity or movement of the target.

impact pattern

A bloodstain pattern resulting from an object striking liquid blood.

insect stain

A bloodstain resulting from insect activity.

mist pattern

A bloodstain pattern resulting from blood reduced to a spray of micro-drops as a result of the force applied

passive bloodstain

occurs when blood drips from a wound or object and are characterized by the presence of drops, drips, cloths, and pools of blood

pool

A bloodstain pattern resulting from an accumulation of liquid blood on a surface

projected pattern

A bloodstain pattern resulting from the ejection of blood under hydraulic pressure, typically from a breach in the circulatory system.

saturation stain

A bloodstain resulting from the accumulation of liquid blood in an absorbent material.

serum stain

The stain resulting from the liquid portion of blood (serum) that separates during coagulation.

splash pattern

A bloodstain pattern resulting from a volume of liquid blood that falls or spills onto a surface.

transfer stain

A bloodstain resulting from contact between a blood-bearing surface and another surface. (transfer pattern, swipe pattern)

transfer pattern

a bloodstain pattern created when a wet, bloody surface comes in contact with a second surface

swipe pattern

A bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another unstained surface, with characteristics that indicate relative motion between the two surfaces.

void

An absence of blood in an otherwise continuous bloodstain or bloodstain pattern.

The 3 layers of the shaft (hair)

cuticle, cortex, medulla

cortex is embedded with _______ ________

pigment granules, main body of hair shaft

hair cuticle

Outermost layer of hair; consisting of a single, overlapping layer of transparent, scale-like cells that look like shingles on a roof.

medulla

continuous, interrupted, fragmented

hair grows in 3 stages

anagen (initial growth), catagen (transition stage between anlagen and telogen), telogen (final phase and hair falls out)

fibers ______ provide individual identification

rarely

2 types of fibers

natural and manufactured

composition of glass

hard, brittle, amorphous substance composed of sand and mixed with metal oxides

what type of glass is most often seen in lab

soda-lime glass

tempered glass

glass to which strength is added by introducing stress through rapid heating and cooling of the glass surfaces (breaks in small fragments, car side windows)

laminated glass

glass given strength by sandwiching one layer of plastic between two pieces of window glass (windshields of vehicles)

radial fracture

crack in glass that extends outward from the point at which the glass was struck

concentric fracture

a crack in a glass that forms a rough circle around the point of impact

hole is wider at the ____

exit

fracture always terminates at an _____ line of fracture

existing

forensic examination of glass

density and refractive index, ICP-MS

most common type of paint evidence is from....

hit and runs