Forensics test 1

cannot be seen directly
can only be seen through lens
formed by eyepiece

Can be seen directly
produced through objective lens

2 lenses mounted at ends of hollow tube
objective lens forms real, inverted magnified image
eyepiece magnifies image into virtual image

base - stand for support
arm - acts as handle
stage - platform to place specimens
stage clips - holds slide, supports specimen
Body tube - hollow tube in wich light passes through objective to eyepiece
Coarse adjustment knob - focuses microscope on specimen, raises and lowers
fine adjustment knob - finer focus, adjusts height in smaller icrements

illuminator - artificially supplied light source
condensor - lens system understage
objective lens - closest to specimen, mounted on revolving nose piece, parfocal scope
eyepiece - closest to eye, magnifies 10x

Transmitted Illumination - for tansparent specimens, light is directed up through stage (sperm, blood fibers)
Vertical illumination - Not transparent specimen (opaque), light source above specimen, look at trace evidence of bulky evidence

image is focused with 1 objective and another objective can be rotated into space and field will remain in focus

Monocular - 1 eyepiece
Binocular - 2 eyepiece

ability of microscope to make the image larger

the ability to form images into fina detail

size of specimen area, area of specimen that ca be seen after magnified
As magnifying power increases - field of view decreases
best to first select low magnification with good general overall view, then switch to higher power

thickness of speciment that is entirely in focus under a scope
AS magnification increases depth of focus decreases

Zacharius Janssen invented first of CLM
uses 2 lenses - objective and eyepiece
Advj - view live organisms
Disadvj - not high mag, power, or detail

2 compound microscopes combined into 1 unit
2 independent lenses joined by optical bridge to a common eyepiece lens
Viewer - looks through eyepiece, observes objects side by side in a circular field
must closely match optical characteristics of obejctives to ensure both specimens are seen at same magnification
vertical - compare opaque objects, bullets and cartridges
transmitted - compare hairs and fibers

used for physical evidence that doesn't require high mag
msot frequently used scope in crime labs
Advj - large working distance, 3 dimentional image, create side up image, wide field of view and great depth of focus
view live organisms
disadv - not high mag power
can be used to locate trace evidence in debris, garments, weapons, tools, bulky items

plane polarized light - confined to a single plane vibration
polarizes - device that permits passage of light waves vibrating in 1 plane
if polarizer and analyzer are parallel - polarized light passes through and is seen by eye
if polarizer and analyzer are perpendicular - no light penetrates, darkness
Biofringent materials - materials that split a beam of light in two light ray components each with its own refractive index

links a light microscope to a computerized spectrophotometer
uses selective absorption spectra of light to characterize mateirals
can view particles under microscope while directing beam of light at specimen to obtain the absorption spectrum
advj - provides added information to characterize trace qualities
Identifies paint, fibers, and ink evidence
displays exact wave length

uses beams of electrons instead of light
direct beams of electrons onto specimens to form an image
uses tungsten filament to emit beams of electrons
disadv - specimens are dad
advj - high mag, high resolution, great depth of focus
look for gunshot residue and elemental composition

examiners can detect elements found in bullets primers (barium, antimony, lead)

scientist examines microscopic evidence to solve crimes

scientist analyzes pollen and spors to solve crimes

link suspect/object to crime scene/victim
prove/disprove suspects alibi
include/exclude suspects
track previous whereabouts of item/suspect
indicate geographical location

first recoreded case of using pollen in case, women found dead, liquid taken from clothes, pollen indicated she was from a different area

sightseeing trip with buddy/ business partner, business went missing, guy claimed he never saw, searched cabin and found muddy boots, traced pollen on boots back to where body was found, guy confessed

guy kidnaps farmer, makes him withdraw money, kills him, walks across cornfield for liquor, robs liquor store, arrested, gloats in jail, another guy tries to get a reward for turning him in, guys clothing analyzed in lab for corn and eyewitnesses

document examienr called in to examine suspect handwriting with ransom note, the looped tail of the y and the unfinished o, wood from attic was same as ladder, tool marks matched his tools

drug officers confiscate cocaine, tracked drug to south america, shipped to canada, come to new york, stopped drug bust by going to location

baby in garbage bag found along river, did spor wash for hair and clothings, pollen matched with boston, identified as b bon

determined that owmen have barr bodies and men don't, karyotype - picture of characteristics lined up, gender and if missing/extra chromosomes
identify with dna from dental pulp and compare teeth to dental records