FINAL EXAM Flashcards
Locard’s Exchange principle
“It is impossible for a criminal to act, especially considering the intensity of a crime, without leaving traces of this presence”
- objects or surfaces which come into contact always exchange trace evidence
Paul Kirk
Wrote “Crime investigation”, considered the father of american forensic science
Passive documentation
- no real insight into the circumstances of the incidence
- investigator guessing at what might be important
active documentations
uses the scientific method; allows investigators to focus on important evidence
“Proper” evidence collection
maintains the integrity of the evidence
- evidence must be sealed
- must be packaged so as to preserve it
- must be free of potential contamination
is safe (from any and all that must encounter it)
- firearms should be unloaded
- sharp objects should be in special containers
- appropriate cautions should be taken with explosives and toxic materials
- cautions should be taken with biohazards
Basic hair structure
- cuticle
- cortex
- medulla
- cortical fusi
- ovoid bodies
- pigment granules
Hair papilla
a peg of connective tissue containing capillaries and nerves
Melanocytes
Cells that produce melanin
Demarcation line
dyed hair
Anagen phase
period of active hair growth
Catagen
The period of breakdown and change of hair growth
Telogen Phase
Resting phase of hair growth
hair growth rate
1/2 inch/month
Caucasoid hair
- 70-100 um
- OVAL cross section
- pigmentation is evenly distributed
- cuticle is medium
Negroid har
- 60 - 90 um
- FLAT cross section
- pigmentation is dense and clumped
Mongoloid hair
- 90 - 120 um
- ROUND cross section
- pigmentations is dense auburn
- cuticle is thick
Somatic Origins
Scalp
Public
Vulvar
Chest
Beard
Axillary
Eyebrow
Eyelash
Limb
Ear
Buttocks
Nose
Cuticle Patterns
- Mosaic
- Petaloid
- Double chevron
- Irregular wave
- Imbricated
Medullary Configuration
Serial ladder
Amorphous Ceulluar
Fragmented
Unbroken cellular
Unbroken vacuolated
Discontinuous Medulla
long chain of color that breaks
Continuous medulla
One unbroken line of color
translucent medulla
medulla that fades into the color of the rest of the hair
Pigment Aggregates
large clumps of pigment to form in the hair shafts
Medullary Index
Medulla divided by hair width
Control sample
- samples used for testing which the values are known
- has to have 25 - 100 hairs
- alternate known or “Anticipated alibi” samples
- “contamination concerns”
Mitochondrial DNA
DNA… in the mitochondria and also is consistently passed down from woman to children (but only woman can pass it down btw)
Feather Terminology
-Rachis
- Calamus
- Quill
- Quill point
- DOwn
- feather fibers
- barbs
- barbules
- Nodes
- Specialized nodes
Spermatozoa Terminology
- Acrosome
- Head
- Middle Piece
- Mitochondrial Sheath
- Tail
Diamond Terminology
Crown (top view)
Gridle (middle silver)
Pavilion (bottom triangle)
Facet Terminology
Table
Bezel
Star
Upper Girdle
lower girdle
Pavilion main
Cutlet
4 c’s of diamonds
Cut, Color, Clarity, Carat
Single cut
17 or 18 facets that are smaller than 4 pts.
1 point equals
0.01 carat (1/100th of a carat)
Table
largest flat facet on the top of a diamond, kinda like a window thru the center
Bezel
kite shaped facets surrounding the table, extends from the table edges to the girdle and are part of the crown
Star
small triangular facets located between the table and the bezel
Upper Girdle
located just above the girdle on the crown
Lwwer Girdle
located just below the girdle on the pavilion of the diamond
Pavilion main
kite shaped facets on the bottom part of the diamond
Cutlet
Small facets at the bottom of the pavilion
Tolkowsky Cut
American cut of diamonds
Carat (Ct) Weight
Used to measure diamonds
- 0.2 grams = 200 mg
- 1 gram = 5 carats
- 1 carat =100 points
- 1 point = 0.01 ct
Karat (K)
- 1 Karat gold (K) = 1/24 pure
therefore, 24k equals 1 pure gold (straight pure gold)
Specific Gravity
dry weight / loss of weight in water
(the relative weight of a mineral compared to the weight of an equal volume of water)
Gemscope
A darkfield stereoscope with fluorescent incident light for color grading
Wood Terminology
Spermatophytes (seed plants)
1. Gymnosperms
a. conifers (soft woods, ie. pine)
2. Angiosperms
a. Diocotyledons (hardwoods like maple)
b. monocotyledons (woody moncots like palm)
Radial plane
Cut that runs directly through the center of a tree trunk, perpendicular to the growth rings
Transverse plane
cross section of a tree that is perpendicular to the y axis of the tree
Tangential plane
cut that runs parallel to the y axis of the tree, but tangential to the growth rings (follows the curve of the rings.)
- tangential, kinda like calculus, the tip of the curve
Cambium
thin layer of cells in a tree that produces new cells and allowed the tree to grow.
- it lies under the bark, rings of a tree tell how old it is right? the further rings are the newer ones, this is where the cambium is locate as it makes new rings from the outside
Bark
Protective outer layer of a tree that protects the cambium from damage
Sapwood
light colored outer layer of wood that carries water or sap from the roots to the leaves (made up of xylem cells)
- converted into heartwood
Heartwood
dark inner layer of wood that provides strength to the tree
- made up of compacted xylem cells that are no longer conducting sap and instead filled with resin
Pith
soft tissue at the center of the tree’s stem or trunk, made up of large, thin walled cells prone to cracking and splitting when placed under pressure.
Softwoods
coniferous trees
Hardwoods
deciduous trees like oak and maple; generally denser and harder.
Woody monocots
palm trees and bamboo that develop woody stems.
Resin cells
specialized cells that produce and store resin
Tracheids
elongated cells in the xylem responsible for water transport
Parenchyma
versatile cells that can store food and secrete substances like resin
longitudinal ray cells
specialized parenchyma that run vertically in the xylem tissue and determine grain direction of wood (the direction in which the wood readily splits or cleaves)
vessel elements
individual cells that form long and continuous water conducting tubes within the xylem
Perforation plates
large specialized openings on the end of walls of vessel elements that allow water to flow freely between them
Soil analysis
involves the examination of color, particle and mineral I.Ding
Petrographic microscope
optical microscope used to i.d rocks and minerals in thin sections
Sequencing glass fractures
observing fracture lines and where they end. A fracture will always end at an existing fracture line
The 4R rule for glass fracture analysis
Ridges on Radial cracks are Right angles to the Rear
- rear is the side opposite to the impact
- this rule does not work on tempered and laminated glass
Radial Fracture
crack will start on the side of the glass that is opposite to applied force
Tangential fractures
crack will start on the same side of the glass as the applied force.
Tempered Glass
cannot easily be reconstructed and it dices without forming ridges
Laminated glass
4R rule is not reliable because the two sheets of glass are restricted in movement
GRIM
Glass Refractive Index Measuring
FTIR
Fourier Transform Infrared Spectroscopy
DRIFTS
Diffused Reflection Infrared Fourier Transform Spectroscopy
ATR
Attenuated Total Reflectance
UV-VIS (MSP)
Ultraviolet-visible spectroscopy
Interferogram vs. Spectrum
Interferogram is a how a sample absorbs infrared light while spectrum shows how strongly a sample absorbs each frequency of IR light
Polystyrene
the standard for FTIR because it has well defined IR absorption peaks
Holmium Oxide
used as a standard in UV-VIS MSP
PyGC (FID)
Pyrolysis gas chromatography combined with flame ionization detector
PyGC-MS
Pyrolysis gas chromatography-mass spectrometry
Colorimetry
science of measuring and describing color
Metamerism
The phenomena where two color samples appear to match under one condition but not under another
Automotive paint layering
Clear coat, base coat, colored coat, primer-surfacer, “e”-coat or electrolytic primer
Decorative flake
interference or metalic
Bullet wipe
dark gray or black ring of material that forms around the entrance of a bullet hole.
Muzzle to target distance determinations
estimating the distance between the muzzle of a firearm and the target surface where the bullet struck
Taggants
chemical or physical marker added to materials to enable testing or detection
Black powder vs double base powders
black powder is traditional gun powder while double base powder is a smokeless powder. Black powder is older and less efficient propellant compared to double base powders
Resolution limits of microscopy
d = 0.61 lambda0 / n(sin theta0
- Unaided Eye: d = 0.1mm (at 25cm)
- LM: d=0.2μm (200nm)
- TEM: d=0.21nm (2.1Å at 50kV)
- SEM: d=3nm (30Å )
SEM Signals (backscatter electrons, secondary electrons, auger electrons, characteristic x rays)
Scanning electron microscope;
- Elastic: Negligible energy loss (back scattered)
- Inelastic: Substantial Energy Loss (Secondary electrons)
- Auger Electrons = when an low energy electron is emitted because a higher energy electron took a vacancy in a lower shell
Characteristic x-rays = outer shell electron fills the vacancy of an inner shell electron
Everhardt-Thornley Detector
(scintillator, light guide, photomultiplier)
Most SEM have this, glass target (scintillator) is struck by an electron. This collision causes produces photons (light). This light is then transported (light guide) and converted into electrical signals (using the photomultiplier).
EDS
EDS: Energy dispersive spectroscopy
- low cost, rapid display of entire spectrum
WDS
Wavelength dispersive spectroscopy
- higher resolution, high count rate, highly quantitative analysis
Electron Scattering
when an electron is deflected from its original path when passing through material
How much an electron is scattered within a material is:
- directly proportional to the atomic number of the material (Z) (high Atm. # = scatter more electrons)
- Inversely proportional to the accelerating voltage (V) of the electron beam (accelerating voltage = less scattering)
Monte Carlo Diagrams
- used to model the probability of different outcomes in a process that cannot easily be predicted due to the intervention of random variables
- Probable high count rate = small carbon peak
- Lesser count rate = significant carbon peak
GSRp Analysis
- Automated Particle Analysis
When a gun fires small particles are generated during the explosion, these particles are deposited on parts of the body and called gunshot residue. - residue goes to clothes, hair, face, fingers, hands etc.
- gunshot residue significantly declines on living subjects after 4 hours
- analyzed with SEM and EDS
X-Ray Fluorescence
a technique for identifying the chemical makeup of a raw material
Solid State Backscatter detector
To collect electrons, the backscatter detector moves under the lens so the electron beam can travel through the hole in its center.
