l4 trace evidence Flashcards
what is Locard’s Exchange Principle
every contact leaves a trace
what is primary transfer? secondary transfer?
primary- direct contact
secondary- indirect, usually intermediate source
what is trace evidence?
Evidence that is transferred is small or even microscopic
what is the most important tool in forensic trace analysis and what is the proper term of this study?
microscope, microanalysis
two types of info you can gain from microanalysis ?
morphology, analytical data
probing matter with energy can tell you the what of a sample? what is this study called?
chemical composition, spectroscopy
which microscope is most likely to be employed first in the examination of evidence?
stereo binocular microscope
use of stereo binocular microscope
preliminary evaluation, location of microscopic particles
stereo binocular microscope is what kind? How does it work?
compound type (more than 1 stacked lens), works using reflected light (like eyes)
second most common type of microscope
compound binocular microscope
what is the use of a compound binocular microscope
collect morphological information
calibrated micrometer placed on EP of microscope that enables accurate measurements to be taken
micrometry
how does a compound binocular microscope work?
transmitted light, uses slides
most important microscope in forensics
comparison microscope
how are we able to see two independent images at the same time using a comparison microscope?
two microscopes joined by an optical bridge
use of comparison microscope
Simultaneously view two independent images in one field
Microscope that enables far greater magnification than any others
Scanning electron microscope (SEM)
briefly explain how a scanning electron microscope works
- beam of electrons swept over area
- beam interacts with surface and slightly below surface of sample
- initial beam removes extra electrons from sample which is converted to image
- x-rays are also created, to obtain chemical info
what is the use of a scanning electron microscope?
generates image and chemical compound of sample at the same time
what is glass? (characteristics)
amorphous solid, hard, brittle, transparent, lacks ordered arrangement of atoms in most solids
common, mass-produced glass usually found in glassware, contains sodium carbonate and calcium carbonate
soda lime glass
similar to lime-glass but with boron added, heat resistant
pyrex glass
what is tempered glass? what is another name for it
when it breaks, it shatters into small pieces so there are no big pieces that will cut you, safety glass
comparing glass consists of..?
- finding and measuring the properties of a piece
- minimizing or eliminating possible sources based on the properties