FORENSIC SCIENCE Physical Evidence

PHYSICAL 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

Criminalistics vs Criminology 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.

Scientific Evidence in the Courtroom 1993 Daubert v. Dow Admissibility 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 1923 Frye v. United States Scientific evidence is allowed into the courtroom if it was generally accepted by the scientific community.

Probative Value of 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”.

Physical Evidence Glass Soil Sand fractures density refractive index characteristic types location Sand

INVESTIGATIONS Observation Experimentation Note Taking Recording data and results Drawing conclusions--putting it all together

GLASS Glass A. 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

GLASS (cont) B. Determining Physical Characteristics 1. Density= mass divided by volume 2. Refractive index--the bending of light waves due to a change in velocity. 3. Fractures a. radial fractures--straight lines that come off the point of impact b. concentric fractures--circular lines around the point of impact

GLASS (cont) C. Used as Evidence 1. 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

SOIL Soil B. The Earth 1. 75%--oceans, seas and lakes A. Definition--the naturally deposited material that covers the earth’s surface and is capable of supporting plant growth B. The Earth 1. 75%--oceans, seas and lakes 2. 15%--deserts, polar ice caps and mountains 3. 10%--suitable for agriculture

Soil (cont) C. Formation 1. Living matter--plants, animals and microorganisms 2. Climate 3. Parent materials 4. Relief--slope and land form 5. Time

Soil (cont) D. Profile E. Composition Topsoil Subsoil Parent material Sand Silt Clay Organic matter

Soil (cont) F. Nutrients--macro G. Nutrients--micro 1. Nitrogen 2. Phosphorus 3. Potassium 4. Calcium 5. Magnesium 6. Sulfur G. Nutrients--micro 1. Manganese 2. Iron 3. Boron 4. Copper 5. Zinc 6. Molybdenum 7. Chlorine

Soil (cont) H. Soil types in the United States 1. 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) I. Used as Evidence 1. 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.

SAND 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.)

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

Sand Examples Great Salt Lake Its unique characteristic is the very round shaped grains. Magnified 30x using a dissecting stereomicroscope.

Sand 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.

Sand Evidence “In every grain of sand is a story of earth Sand Evidence “In every grain of sand is a story of earth.” --Rachel Carson 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

Unusual “Physical Evidence” Crazy 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.