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Crim 355 Final Exam review.docx

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Simon Fraser University
CRIM 355
Jodie- Ann Warren

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 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 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 dont 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 Need to collect blood from several sites to compare Urine Specimen Primary fluid for screening and confirmation Not so good for quantitation Excretory products Indicates prior exposure Easily available, non-invasive Useful for postmortem alcohol determinations Risk of tampering Hair Specimen Good for screening over many months Controversy over whether IN or ON hair Canada criminal testing only US criminal and employment testing Vitreous Humour Good for determining alcohol levels after death as is a self contained unit not in contact with other body fluids. Other Specimens Liver, kidneys, gastric contents, bile, brain, lungs, injection site, CSF, bone marrow, maggots, vitreous fluid, stains, saliva, meconium, POST-MORTEM Non-biological exhibits: paraphernalia including syringes, spoons, pipes; residues including powders, stains, food; medicine including prescriptions, pills; seized at the scene? Analytical Considerations No single analytical scheme to detect everything Use repertoire of standard methods, modify according to nature of case as well as type and amount of specimen Exclude or indicate the presence of a drug, poison or class of compounds Presumptive then confirmatory tests Presumptive Screening Rapid, sensitive, NOT specific, very useful to exclude a drug or class of drugs and to indicate possible drugs Confirmatory Methods Sensitive, specific, combination of chromatography and spectrometry (2 methods) Interpretation Drugs? Amount? Symptoms? = behaviour
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