FSC239Y5 Lecture Notes - Lecture 2: Firing Pin, Composition B, Combustibility And Flammability
1. Lecture 2: Physical Evidence
Locard’s Principle: Every contact that leaves a trace.
oWhat forensic science is based on.
Trace Evidence: Refers to physical evidence that is found in small but measurable
amounts, such as strands of hair, fibers, or glass (used to establish a link).
Physical Evidence: Anything that maybe found, by investigators, to have a connection
with a crime (used to establish a link).
oNon-biological (Example: footprints, tire marks).
oBiological (Example: DNA, semen).
Examples of Types of Evidence:
oFingerprints
oDrugs
oTool marks
oGlass
oExplosives
oBlood, semen, saliva
oHair and fiber
Looking for Trace Evidence:
oLighting is key.
oOblique lighting (good for impressions).
oAlternative light source: Any light other than natural light. (Sometimes the
different color flashlights/UV light make it easier to see biological evidence; such
as semen, urine, and saliva).
Examination of Physical Evidence:
oIdentity:
Physical properties.
Chemical properties.
oCompare:
find more resources at oneclass.com
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Document Summary
Locard"s principle: every contact that leaves a trace: what forensic science is based on. Trace evidence: refers to physical evidence that is found in small but measurable amounts, such as strands of hair, fibers, or glass (used to establish a link). Physical evidence: anything that maybe found, by investigators, to have a connection with a crime (used to establish a link): non-biological (example: footprints, tire marks), biological (example: dna, semen). Examples of types of evidence: fingerprints, drugs, tool marks, glass, explosives, blood, semen, saliva, hair and fiber. Physical properties: a change in state without change in chemical composition: color, texture & state, odor, boiling point & melting point, density, solubility. Chemical properties: change in change in chemical composition (chemical bonds): flammability, radioactivity, oxidation, enthalpy of formation, heat of combustion. Did not originate from the same source : properties measure agreed. All evidence bears class characteristics (general source).
