1 forensic science physical evidence 2 physical evidence you can lead a jury to the truth but you...
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FORENSIC SCIENCEFORENSIC SCIENCE
Physical Evidence
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PHYSICAL EVIDENCEPHYSICAL EVIDENCE
You can lead a jury to the truth but you can’t make them believe it. Physical evidence cannot be intimidated. It does not forget. It doesn’t get excited at the moment something is happening--like people do. It sits there and waits to be detected, preserved, evaluated and explained. This is what physical evidence is all about. In the course of the trial, defense and prosecuting attorneys may lie, witnesses may lie, the defendant certainly may lie. Even the judge may lie. Only the evidence never lies. --Herbert Leon MacDonell, The Evidence Never Lies
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Criminalistics vs Criminalistics vs CriminologyCriminology
Criminalistics is the scientific examination of physical evidence for legal purposes.
Criminology includes the psychological angle, studying the crime scene for motive, traits, and behavior that will help to interpret the evidence.
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Scientific EvidenceScientific Evidencein the Courtroomin the Courtroom
1923
Frye v. United States
Scientific evidence is allowed into the courtroom if it was generally accepted by the scientific community.
1993 Daubert v. DowAdmissibility is determined
by: Whether the theory or
technique can be tested Whether the science has been
offered for peer review Whether the rate of error is
acceptable Whether the method at issue
enjoys widespread acceptance. Whether the opinion is relevant
to the issue
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Probative ValueProbative Valueof Physical Evidenceof Physical Evidence
Legally, probative value is the level at which evidence provides proof of the crime.
Associative value is used to place a suspect at a crime.
Product rule--how often something occurs in nature or the “real world”.
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Physical EvidencePhysical Evidence
Glass• fractures• density• refractive index
Soil• characteristic• types• location
Sand• characteristic• types• location
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INVESTIGATIONSINVESTIGATIONS
ObservationExperimentationNote TakingRecording data and
resultsDrawing conclusions--
putting it all together
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GlassA. Common Types
1. Soda-lime--used in plate and window glass, glass containers, and electric light bulbs
2. Soda-lead--fine table ware and art objects
3. Borosilicate--heat resistant, like Pyrex
4. Silica--used in chemical ware
5. Tempered--used in side windows of cars
6. Laminated--used in the windshield of most cars
GLASSGLASS
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GLASS (cont)GLASS (cont)
B. Determining Physical Characteristics1. Density= mass divided by volume
2. Refractive index--the bending of light waves due to a change in velocity.
3. Fracturesa. radial fractures--straight lines that come off the
point of impact
b. concentric fractures--circular lines around the point of impact
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GLASS (cont)GLASS (cont)
C. Used as Evidence1. Class characteristic--the type of glass
may be evident at the crime scene
2. Individual characteristic--can piece the glass in the piece of evidence from the crime scene
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SOILSOIL
SoilA. Definition--the naturally deposited material that covers the earth’s surface and is capable of supporting plant growthB. The Earth
1. 75%--oceans, seas and lakes2. 15%--deserts, polar ice caps and mountains3. 10%--suitable for agriculture
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C. Formation
1. Living matter--plants, animals and microorganisms
2. Climate
3. Parent materials
4. Relief--slope and land form
5. Time
Soil (cont)
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Soil (cont)Soil (cont)
D. Profile– Topsoil– Subsoil– Parent material
E. Composition– Sand– Silt– Clay– Organic matter
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F. Nutrients--macro1. Nitrogen
2. Phosphorus
3. Potassium
4. Calcium
5. Magnesium
6. Sulfur
G. Nutrients--micro1. Manganese
2. Iron
3. Boron
4. Copper
5. Zinc
6. Molybdenum
7. Chlorine
Soil (cont)Soil (cont)
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H. Soil types in the United States1. Pedalfers--soils rich in clay, iron oxides, and
quartz fragments where rainfall exceeds 65 centimeters per year; mostly the eastern half of the country
2. Pedocals--soils with less clay and rich in calcium carbonate where rainfall less than 65 centimeters per year; the western half of country except for the Pacific coast region
Soil (cont)Soil (cont)
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SOIL (cont)SOIL (cont)
I. Used as Evidence1. Class characteristic--the type of soil may
have similar characteristics at the primary and/or secondary crime scene, on the suspect or on the victim
2. Individual characteristic--only if the soil has an unusual characteristic such as pollen, seeds, vegetation, or fragments.
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SANDSAND
Sand is the term applied to natural particles with a grain diameter between 1/16mm and 2 mm.
Its color and contents is dependent upon the parent rock and surrounding plant and animal life.
(The photo on the right shows color differences in sand from six locations around the world.)
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SAND (cont.)SAND (cont.)
Types 1. Continental sands--formed from weathered
continental rock, usually granite
2. Ocean Floor sands--formed from volcanic material, usually basalt
3. Carbonate sands--composed of various forms of calcium carbonate
4. Tufa sands--formed when calcium ions from underground springs precipitate with
carbonate ions in salt water in a salt lake
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Sand ExamplesSand Examples
Great Salt Lake
Its unique characteristic is the very round shaped grains.
Magnified 30x using a dissecting stereomicroscope.
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Sand ExamplesSand Examples
Black Sands of Hawaii
Its unique characteristic includes the black grains made of basalt lava from volcanic eruptions.
Magnified 30x using a dissecting stereomicroscope.
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Unusual “Physical Evidence”Unusual “Physical Evidence”Crazy CriminalsCrazy Criminals
Donna Clark, 26, and Paul Kramer, 31, face charges in New Jersey. Clark allegedly grabbed $216 worth of film and walked out of a drugstore. The couple’s names were provided by their 6-year old son, who was in the store at the time but who was forgotten by the couple as they made their getaway.
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Sand EvidenceSand Evidence“In every grain of sand is a story of earth.” --Rachel “In every grain of sand is a story of earth.” --Rachel
CarsonCarson
Class characteristic--the type of sand may have similar characteristics at the primary and/or secondary crime scene, on the suspect or on the victim
Individual characteristic--only if the sand has an unusual characteristic
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