Forensic Microscopes, Fibers, Fingerprints, Forensic Microscopes, Forensic Hair Analysis, Crime Scene Test

synthetic fibers

fabrics made from chemicals, rather than natural sources

fiber

the smallest indivisible unit of a textile

plant fibers

fibers made up of plants cells. They are grouped by the part of the plant they come from, like seed, stem, fruit, and leaves.

direct transfer

the passing of evidence, such as a fiber, from victim to suspect or vice versa

secondary transfer

the transfer of evidence such as a fiber from a source (for example, a carpet) to a person (suspect), and then to another person (victim)

coir fiber

fiber obtained from the fibrous mass between the outer shell and the husk of the coconut

hemp

a type of fibrous herb that produces material suitable for making rope.

cotton fiber evidence

Fiber evidence is gathered with:

special vacuums, sticky tape, and forceps (tweezers)

chemical analysis of fibers

• As a whole, dye analysis, chromatography

microscopic analysis of fibers

Color, X-section, Diameter, and surface appearance

rayon fibers

synthetic- like cotton, soft, smooth, strong, resistant to moths, and can retain water well- used to make velvet

Nylon fibers

are smooth, strong, lightweight, elastic, and lustrous

Polyester fiber

most widely used man-made fiber, wrinkle resistant

Acetate fibers

synthetic- soft, smooth, dry, weak, lustrous and heat-sensitive, satins and taffetas- shiny and lustrous looking fabric

Acrylic fibers

synthetic fibers that are soft, lightweight, resilient, and heat-sensitive.

Often used as a replacement for wool because they have a very similar feel to wool. Also often used as a less expensive alternative to cashmere, as they have a very similar appearance.

warp

a lengthwise yarn or thread in a weave

Weft

the horizontal threads interlaced through the warp in a woven fabric

Tabby Weave

basic weave where the weft thread is woven in the "over and under" pattern

twill weave

two over, one under, creates a diagonal texture on the surface, less wrinkly, more durable, shows less dirt that a tabby (plain)

satin weave

A weave that produces a smooth, shiny-surfaced fabric resulting from passing the weft yarn over and under numerous warp yarns ( 3/1, 4/1. 5/1, or more) to create long floats.

basket weave

multiple horizontal and multiple vertical strands

knit weave

-to weave things together to connect them with interlooping fibers usually yarn for clothing

courses and wales

wale is a column of loops running lengthwise, corresponding to the warp of woven fabric; a course is a crosswise row of loops, corresponding to the filling.

sampling and testing fibers

if there is a sufficient amount to test and have leftover material- perform the fiber burn test

if there is NOT a sufficient amount, examine with polarizing microscope & scanning electron microscope

The physical characteristics of fibers may be examined by the following:

Counting the number of filaments

Calculating the density of the fiber

Evaluating the Refraction Index of the fiber

Checking the fiber for fluorescence

Natural fibers come from

plants, animals, minerals

The most common fiber

cotton, easily woven & dyed

minerals in fibers such as asbestos are very durable. These fibers are used in all of the following except: rope, shingles, floor tiles, brake liners

rope

True/false: synthetic fibers do not contain any natural fibers.

False

A characteristic of a natural fiber is that they

are affected by microscopic organisms

What types of observations are used to help identify a specific fiber?

• smell of the burned fiber

• on contact with the flame does the fiber melt?

• color and structure of the residue (ash) left after the fiber

burns

• afterglow

• color of the smoke

Fibers are an excellent source of trace evidence because

They are easily transferred from victim to suspect, they are often overlooked by a suspect, they can be easily collected and stored

microscopic examination of synthetic fibers

Do NOT have any internal structures

Must be viewed in cross section under an electron microscope

microscopic examination of natural fibers

have internal structures, look like small holes

Francis Galton

Wrote the book "FIngerprints" which was the first statistical proof of the individuality of fingerprints.

Will West Incident

showed that the Bertillion System was unreliable and paved the way for fingerprints to be the main means of identifying a criminl

Dermal papillae

layer of skin tissue gives rise to the fingerprint

Fetal development of fingerprints are normally complete by the end of the 3rd month.

fingerprints develop

Pores

Fingerprints are populated by ___________ that allow perspiration to be released on the skin.

Loops, arches whorls

What are the 3 major classifications of fingerprints?

Loops - 60%

What is the most common fingerprint pattern? What percentage of fingerprints belong in that classification?

Arches - less than 5%

What is the rarest fingerprint category? What percentage of fingerprints fall into this category?

Whorls -30%

Fingerprint category with two deltas

Arches

Fingerprint classification with no deltas

Loops

Fingerprint classification with one delta

Ulnar loop

Print with one delta, loop opens to the pinky/ ulna bone

Core

In a fingerprint, the central pocket is also known as the ____________.

radial loop

Name this fingerprint: left hand

plain whorl

Name this fingerprint:

double loop whorl

Name this fingerprint:

Plain arch

Name this fingerprint:

central pocket whorl

Name this fingerprint:

tented arch

Name this fingerprint:

Automated Fingerprint Identification System

What does AFIS stand for?

Bifurcation (fork)

Name this minutiae:

Eye

Name this minutiae:

No! A trained examiner uses possible matches provided by AFIS to make the match.

Does AFIS conclusively match fingerprints? If not, what or who does?

No minimum exists. There is a recommendation of 8- 12.

How many points of minutiae are required to substantiate a match?

Powder

Fingerprints deposited on a non-porous surface should first be developed with....

Chemical treatments

Fingerprints left on soft or porous surfaces should be generally processed with...

Cyanoacrylate fuming (superglue method)

Chemical treatment that is not actually a chemical reaction. It is a vaporization and deposit that produces a permanent white print.

Non-porous

What type of surface is superglue fuming appropriate for?

Iodine fuming

Type of chemical treatment that visualizes a non-permanent brown fingerprint...

Ninhydrin

Type of chemical process that visualizes a purple non-permanent print.

Amino acids

Ninhydrin reacts with what in a fingerprint?

Porous

What type of surface is Ninydrin processing appropriate for?

Photographed

What must be done with non-permanent prints?

Patent prints

Fingerprints that are made by fingers coated with a substance, such as blood, ink, dirt, etc.

Latent prints

Fingerprints made by the transfer of oils or perspiration present on the finger; invisible to the eye.

Plastic prints

Fingerprints that are three-dimensional impressions made in pliable surfaces, such as wet paint, wax, soap, putty.

AFIS

Systems which are designed to place fingerprints into computers so as to allow the computer to categorize, compare, and match fingerprints.

Minutiae

Characteristics of ridges; include ridge endings, bifurcations, lakes, short ridges, and cross¬overs.

Bifurcation

The forking, or dividing, of one line into two or more branches.

Core

A structure in the print that is the center line or lines of the print.

Delta

A point in loop and whorl prints that lies within an often triangular, three-pronged or funnel-shaped structure.

The average fingerprint has how many points of identification?

up to 150 minutia

In addition to fingerprints, NGI can store these kinds of records.

1. iris identifications, palm prints, facial recognition, and other characteristics

The Three Principles of Fingerprints

1. A fingerprint is an individual characteristic; no two fingers have yet been found to posses identical ridge characteristics.

2. A fingerprint will remain unchanged during an individual's lifetime.

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

Why are fingerprints left on things we touch?

Sweat and oil is constantly secreted on to the surface of finger ridges. When skin comes in contact with a surface, these fluids are left behind in the shape of a print.

Why do humans have fingerprints?

Increase friction and improve grip

1910 Jennings Case

first case solved in the US using fingerprints, a man broke into a house and attacked a teenager, the father defended his daughter and was killed.

1892 Rojas Case

1st case ever solved using fingerprints, a mother murdered her own children and tried to blame it on an ex-lover