CSI exam 3 lecture 2

when do fingerprints develop in human fetus

12 weeks

fiction ridge skin

skin on hands and feet

outer appearance of friction ridge skin reflects its functions:

1. ridges and pores allow grasping of objects

2. creases allow skin to flex

3. ridges, creases, mature scars are valuable and durable morphological identifying features

3 main layers of skin

epidermis, dermis, hypodermis

epidermis

outer layer of skin that prevents water loss, acts as receptor, provides protective barrier

dermis

connective tissue that provides structural support to epidermis, also reserves blood, aids in sensory reception, and helps regulate temperature

hypodermis

lies below the dermis, loose connective tissue containing fats and acts as an edgy reserve for the body

epidermis consists of 4 main cell types:

keratinocytes, melanocytes, langerhans cells, merkel cells

keratinocytes

primary cells of epidermis that undergo most change and are eventually lost at the surface

dermis includes network of nerve branches that control functions such as:

blood flow, secretions, touch, pain, itch, temperature

sweat glands

1. friction ridge skin has the largest and highest concentration of eccrine sweat glands on the body

2. eccrine sweat glads help regulate body temperature and excrete metabolic waste thru sweat

3. sweat glands penetrate deep into dermis/hypodermis depending on location

4. sweat is what fingerprints are primarily made of

fingerprints composition:

98% water, 2% grease, oil, salts, amino acids

science of fingerprints used on two fundamental principles:

individual: no two fingerprints have been found to be exactly the same

permanence: fingerprints develop around the third moth if gestation and remain consistent through a person’s lifetime

3 basic forms of fingerprints

1. latent: considered to be invisible prints created by depots of normal body secretions

2. patent: caused by the deposit of contaminants and visible to naked eye

3. plastic: impressions where a print has been deposited in a soft surface such as wax

facts that affect probability of identifiable prints on given surface:

1. amount of pressure between friction ridge and substrate

2. duration of contact and nature of contact

3. substrate characteristics

4. depositor characteristics

level 1 details

1. loops (65% of population)

2. whorls (30% of population)

3. arches (5% of population)

level 2 and 3 details

level 2: dot, ending, bifurcation, enclosure

level 3: pores, incipient ridges, creases, warts, scars

basic types of surfaces:

1. porous: items that can absorb moisture

2. nonporous: any surface that does not absorb moisture

3. special conditions: human skin, adhesive, bloody prints, etc.

porous processing methods

DFO, ninhiydrin, physical developer, silver nitrate, iodine fuming, IND, zinc chloride

DFO

reacts with alcohols which reacts with amino acids to produce a yellow fluorescence, useful for dark porous items

ninhydrin

reacts with amino acids commonly found in latent print residue forming purple compound known as ruhemanns purple

physical developer

silver based liquid reagent reacts with components of sebaceous oils and produces a grey/black color

silver nitrate

reacts with chloride and salt components o produce a brown color

iodine fuming

reacts with fatty and oily components to produce a reddish-brown color

IND

reacts with amino acids and eccrine components to produce a yellow fluorescence

zinc chloride

reacts with ninhydrin and IND to produce an orange fluorescence

nonporous processing methods

powders, superglue (cyanoacrylate) fuming, dye stains, small particle reagent, sudan black

powders

powders should be selected based on how they contrast with substrate being processed, powders adhere to oily reside on fingers

if an item has a porous and non-porous side, process non-porous side first

conventional powders

black, white, blue, dual contrast, biochromatic, etc.

used with fiberglass brush

fluorescent powders

green, pink, yellow, etc.

used in conjunction with alternate light source and barrier filters/goggles

used w/ feather brush

magnetic powders

black, white, variety of colors

useful for shiny/coated materials, styrafoam, treated wood

used w/ magnetic brush

different types of latent tape

clear, frosted, polyethylene

polyethylene tape and gel lifts

useful for curved/textured surfaces

cyanoacrylate fuming

developed by japanese- superglue fumes react with latent print, plasticizing and stabilizing print

reacts with eccrine components of fingerprints to produce a white residue on fingerprints

dye stains

reacts with cyanoacrylate deposit and produces a fluorescence, used in conjunction w alternate light source and barrier filter

(MBD, ardrox, M-star, m-stardrox, rhodamine 6G, RAM, safrinin O

small particle reagent

reacts with sebaceous lipids and fatty components and results in a color dependent on type of SPR used (white or black)

sudan black

reacts with sebaceous components to produce a dark blue color

special conditions processing methods

RUVIS, human skin, sticky side powder, wet top, crystal violet, bloody fingerprints, camphor, RECOVER, gun bluing

reflected-UV imagine systems (RUVIS)

uses UV/C light to visualize latent prints before physical processing/development

can damage DNA, make sure all DNA processing done beforehand

human skin. (machine paper technique)

useful for close/prolonged contact or strangulation cases

machine paper rolled w/ gentle pressure onto skin, magnetic powder applied to surface in contact w/ skin

Moonglo and Midnight Blue commonly used

sticky side powder(lab prepped) and wet wop(commercially prepped)

processing methods for the adhesive side of tapes, they react with sebaceous and liquid components and result in either a black or white color

crystal (Gentian) violet

reacts with epithelial cells and proteins to produce a purple color

bloody fingerprints

reacts with either heme or protein component of blood, color is dependent on reagents used

ashleys reagent

reacts w/ proteins produces purple

diaminobenzidine (DAB)

reacts w/ heme produces brown

leucocrystal violet (LCV)

reacts w/ heme produces purple

amido black

reacts w proteins produces dark blue/black

coomassie blue and crowles double stain

reacts w/ proteins produces blue

fluorescin

reacts w/ proteins produces yellow fluorescence

hungarian red

reacts w/ proteins produces red

camphor

useful for metal surfaces

exposes surfaces to see and heat rising from burning material, smoke adheres to surface and smoke and heat react w latent print to stabilize it

RECOVER

foster and freeman have RECOVER latent processing chamber designed to process for latent prints on untreated metals (knives fired cartridge casings)

utilizes sulfar fuming process that reacts w fingerprint oils that have corroded the metal

gun bluing

reacts with eccrine/sebaceous components to produce a black color, useful for brass/nickel cartridge surfaces

chain of custody

when receiving items to process for latents, make sure to sign for them, open packaging in way that does not damage initial evidence seal, when finished processing reseal.

when packaging latent cards, make sure appropriate label is affixed to packaging, include case #, date of collection, case type, name of collector, and location of collection. when sealant the packaging, seal evidence tape w/ initials and date

case notes

should include case #, date of processing page #, and initials on each page

when describing processing methods done on piece of evidence, include unique identifier for item being processed, processing sequence done, and result of those methods

photographing fingerprints

cam should be in aperture priority. manual, flexible should be RAW or TIFF, lowest ISO possible, f-stop between f/11-f/22, shutter adjusted

include scale w/ case #, identifier, and initials of photographer

photograph ridge detail b4 processing, frequently done w/ bloody prints

recording exemplars

can be just of fingerprints or entire hand, recorded on ten-print card

full prints (major case prints)

rolled fingerprints, full finger, the pal. writers rest, trigger area, plain impressions (4 finer taken simultaneously)