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CRIM 355
Jodie- Ann Warren

CRIMINOLOGY 355 FINAL EXAM STUDY GUIDE Forensic ChemistryScience of everydayStudy of nonbiologicalTRACE EVIDENCEExamples paint BEs glass fibers drywall glue cleaner fluid adhesive tape assault where people are bound Qualification for Forensic ChemistryBachelor of Science Honors is minimumBasic training in lab under a mentor 15 months Types of Crime requiring Forensic ChemistryHit and runsglassBE window framesArsonsBombingTerrorism Determining Significance of Chemistry EvidenceClass evidenceMust determine significance of evidenceIs there a match And if so does it mean anythingNot useful without a comparison database to determine probability of someone else have that evidenceHow common is the evidenceMust develop a databaseExample glass at a scene o How common is that sort of glass o If common does it mean anything o Physical properties do they matchGlass on regular people o Mall study o How much class on them o On shoes 30 o Clothes2How valid is the databaseDoes it fit this personhow likely is it this person could innocently have this evidenceGlass on clothing is rare but what if the guy is a glazerSome things are very common in some situations and very rare in othersMore than one type of class evidenceThe more there is the more significantmultiple probabilitiesFibresNatural fibres animals or plant sourcesManmade fibresPolymers eg Nylon large number of atomsPolymers also include paint adhesives plasticsClass evidence Fibre ExaminationCharacteristics o Color o Striations on fibre o Crosssectional shape o Refractive index o Infrared spectrophotometryHow rare is the fibre 1PaintIs everywhereCars all have atleast 4 layers normally could have as many as 7Match to database of car colorsChemically examine paint eg ChromatographyIf repaint jobmore significant but harder to find ArsonMay be direct arsonMay be to disguise a crimeVery difficult to destroy bodyUsually lots of evidence left behindAccelerant used glass chemical mixtures kindlingWhat it purposely setSample must take a controlGasoline gas chromatography o Separates into component parts o Can identify type of gasoline CombustionRapid combination of oxygen with another substance accompanied by production of noticeable heat and lightExothermic reaction a chemical transformation in which heat energy is liberatedHeal of combustion the heat liberated during combustionEndothermic reaction a chemical transformation in which heat energy is absorbed from the surroundingsGlowing combustion combustion on the surface of a solid fuel in the absence of heat high enough to pyrolyze the fuelSpontaneous combustion fire caused by a natural heat producing process in the presence of sufficient air and fuel3 Requirements must be satisfied to initiate and sustain combustion 1 A fuel must be present 2 Oxygen must be available in sufficient quantity to combine with the fuel 3 Heat must be applied to initiate the combustion and sufficient heat must be generated to sustain the reactionExplosions bombsUsually homemadeExplosion combustion with release of gases which expand with the heatVery fastIf confinedpipe bombsharpnelLarge blastgases escape 7000mphGale forceknocks over buildings walls kills Classification of explosivesBased on speed at which the explosive decomposesLow explosives o Speed of deflagration burning o Rapid oxidation heat light subsonic pressure wave o Throwing or propelling motion o Normally just burn o Black powder smokeless powder o Eg Fuse to gunpowder o Lethal when confined Pipe bombHigh explosives o Speed of detonation o Creation of supersonic wave o Instantaneous build up of heat and gases o Primary explosives ultra sensitive to heat shock or friction detonate violently instead of burn Primers blasting caps o Secondary explosives insensitive to heat shock or friction Burn rather than detonate if in open air eg dynamite TNT etc o Bombs must be detonated by an initiating explosion 2
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