CRIM 355 Study Guide - Final Guide: Stippling, Chisel, Nuclear Dna

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Forensic Chemistry
Science of the everyday
Study of NON-BIOLOGICAL trace evidence
Locard exchange principle
Chemists involvement
Analysis
Qualitative and quantitative analysis
Techniques of analysis chromatography, electrophoresis, spectrophotometry
Techniques of analysis
Basic chemistry techniques
Chromatography
Electrophoresis
Spectrophotometry
Chromatography
Separates substance into components (so purifies them)
Gas Chromatography separates based on distribution between liquid and gas phase
Gas chromatograph (GC) - inject sample
Pyrolysis adds heat, e.g. paint chip-gas
High-Performance Liquid Chromatography (HPLC)
Thin-layer Chromatography (TLC)
Electrophoresis
Separates substances on basis of electrical potential
Spectrophotometry
Different substances absorb light in different ways
Used to identify
Mass Spectrometry (MS)
Gas chromatography tentative ID
GC +MS (GC/MS) positive ID
Very basic techniques, first year chemistry
Significance
Identifying substance
Class evidence in order to have value must determine significance
May have high or low significance, if rare more significant
How common is evidence?
Develop database parent population
How valid is your database?
Does it fit this person (i.e. guy with glass on clothes) or how likely is it that this
person could innocently have this evidence?
Suspect must fit in research population
What is population/situation
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More than one type of class evidence
Cumulative the more there is the more significant multiplies probabilities
Fibers
Natural fibres or manmade
Characteristics of fibres colour, striations, cross-sectional shape, refractive index
How rare is the fibre? Circumstances?
Paint
Cars all have at least 4 layers normally
Match to database of car colours
Chemically examine paint
Arson
Chemist may attend and may be special fire investigators
Arson may be fir the sake of the fire, for insurance purposes, to disguise another crime
Was it arson?
Was there an accelerant? gas, chemicals, kindling, bounce
Significance? Where is the accelerant found?
Samples
Collect sample including a control
If an accelerant is found, is it also on control?
If found on control then maybe not used as an accelerant
Explosions, bombs
Was a timer used?
What type of bomb, made of what traceable?
Type of explosive, made of what traceable?
Bombs explosive, timers, detonators, fuses, batteries, duct tape
Explosion - combustion with release of gases, which expand with the heat
Very fast
Large blast with gases escaping >7000 mph
Gale force winds knocking over buildings, walls and kills
Classification of explosions
Low explosives speed of deflagration (burning) rapid oxidation, heat, light,
subsonic pressure wave
High explosives speed of detonation creation of supersonic shock wave
instantaneous build up of heat and gases
Low explosives
Throwing or propelling motion, normally just burn
Black powder, smokeless powder
Lethal when confined pipe bomb shrapnel
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High explosives
Primary explosives ultra-sensitive to heat, shock or friction. Detonate violently
instead of burn, e.g. primers, blasting caps
Secondary explosives insensitive to heat, shock or friction. Burn rather than detonate
if in open air, e.g. dynamite, TNT
Bombs must be detonated by an initiating explosion
Explosives
Early days high explosives nitroglycerin and pulp dynamite
Now ammonium nitrate based e.g. water gels, emulsions and ANFO
Ammonium nitrate manure, easily available, washes away, significance
Forensic Toxicology
Detection of drugs and poisons, interpretation in terms of physiological and behavioral
effects
Toxicologist assist in establishing the true cause of death, provide a basis for
intoxicated behavior, provide a clue to clinical history when the subject is unable or
unwilling to do so, assist in establishing the truth of statements as “I was high and so I
don’t remember”
Criminal cases- murder, attempted murder, manslaughter, assault, physical, sexual,
chemical weapon, impaired driving, poisoning, noxious substances, food and product
tampering, parole and probation violations or what is it?
Non criminal cases- coroner or ME lab postmortem toxicology, Health Canada:
Bureau of dangerous drugs - controlled drugs and substances act violations, private labs
employee screening
Caveat Dose makes the poison
Anything can be a poison-too much water or too much Oxygen can kill eg water dilutes
blood and then shuts down the kidneys/breathing in pure oxygen can kill as well
Toxicological Investigation - Analytical
What is it? Select a specimen, extract compounds, separate compounds, identify
drugs/poison, quantitate drugs/poisons
Toxicological Investigation - Interpretation
When was last dose taken? Was it acute or chronic? How was it taken IV, oral etc.?
What was the level at an earlier time? What symptoms would be present: Is the level
therapeutic, toxic or fatal? How much was taken?
Blood Specimen
Good for screening, confirmation and quantitation
Primary index for drug/poison effects
Invasive, or may not be available
Postmortem redistribution of drugs
Alcohol production by body after death
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