What is Forensic Science?
Background: *Society is regulated by laws, laws depend on enforcement. *The legal system has turned to science for accurate and objective information about crimes. *Science can address many things, but not everything. Text Definition: Forensic Science is the application of science to those laws that are enforced by supplying the courts with objective information about a crime in an effort to help the courts establish the truth.
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Specialties In Forensic Science
Forensic Engineers-Conduct failure analysis, accident reconstruction, fire/explosion reconstruction
Forensic Odontology-Examine dental remain/bite marks Forensic Entomology-Use knowledge of insect life cycle to determine time of death Forensic Psychology-Behavior profile, Forensic Anthropology-Examine skeletal remains Forensic Pathology-Determine cause and manner of death (Med. Examination.)
Logic and Reasoning
Deductive Reasoning – Use all available data/evidence to create 1 complete explanation. Inductive Reasoning – The explanation uses only some facts while ignoring others. (Framed/Pseudoscience)
Observations in Forensic Science
Scientific observation falls into 2 categories: 1) Objective = report only facts or data as known information (colorless, yellow liquid) 2) Subjective = observation that introduces your own personal opinion or bias. [pretty, ugly, gross yellow color]
Types of Observations 1) Qualitative – describes qualities (physical) and characteristics 2) Quantative – observation where you measure a charx to generate numerical data with units (5 ml)
Observation Lab Background Info
Types of Changes
I. Chemical Changes = Chemical Reactions, rearrangement of atoms
Sample Chemical Reaction (Double displacement)
AB + CD AC + BD
A. Temperature Changes -feels cold, reaction absorbs heat = endothermic -feels hot, releasing heat energy = exothermic B. Gas Produced -bubbles in liquid -vapor above liquid C. Precipitate Forms solid particles are made when two or more liquids are combined may look hazy (=opaque) when mixed in liquid often settles to the bottoms of glassware D. Color Changes mixing produces unrelated color vocabulary: Colorless = no color Clear = transparent, can see through it Opaque= can’t see through it (see precipitate) II. Physical Changes =changes in condition or appearance color may changes due to : 1. mixing two colors (red + blue= purple) 2. diluting a color with second liquid III. No observable changes NR= No Reaction
Physical Evidence:
Edmond Locard ( French , 1880) …there is a cross-transfer of physical evidence between the objects in question and the perpetrator. Physical Evidence- Any physical item that can help prove a crime has occurred. Fingerprints Foot/tire prints Fibers Soil Skin/tissue/DNA cells Hair Documents blood/ blood spatter glass drugs paint plants tools/ tool marks bite marks
Weapons
2 kinds of testing done on P.E.
1. Identification- unknown substances identified by name 2. Comparison- analysis that subject the evidence & suspect material to the same tests to determine if they came from the same source. a. Class characteristic physical evidence can only be associated with a large group & never a single source. Probability used. EX: Blood types, hair, fibers, ink
b. Individual characteristic physical evidence can be associated with a single source of fingerprints EX: fingerprints, fired bullets, shoe impressions, broken glass, DNA