Forensic Science Set Three
What is a radial fracture pattern?
A Radial fracture pattern—radiate out from the origin of the impact; begins on opposite side of force
What is Neutron Activation Analysis of hair?
A hair is bombarded with neutrons while inside the core of a nuclear reactor. They collide with the hair emitting gamma radiation of a characteristic energy level. In a single hair sample, 14 different elements can be identified.
What is a spectrometer and how is it used in the analysis of fiber?
A spectrometer measures the bending of a ray of light as it passes from air into a solid or liquid
What factors will increase the probative value of the soil?
A. B. C. D. Manufactured particles
What was the holding in 1993 case 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
What are the racial differences in Asian hair?
Asian Hair Densely distributed pigments; arranged in large patchy areas or streaks. Medulla: prominent (often broad and continuous) Cuticle: thick Cross-sectional shape: round
What is associative value of trace evidence?
Associative value is used to place a suspect at a crime.
What are the standards for collection of fiber evidence?
Bag clothing items individually in paper bags. Make sure that different items are not placed on the same surface before being bagged. Make tape lifts of exposed skin areas of bodies and any inanimate objects Removed fibers should be folded into a small sheet of paper and stored in a paper bag
What is Borosilicate glass?
Borosilicate--heat resistant, like Pyrex
How does burning a fabric aid in its fiber identification?
Burning--how the fiber burns, the odor and the appearance of the residue
What is an absorption line?
By passing light through something to produce a spectrum, the analyst can read the resulting lines, called "absorption lines." That is, the specific wavelengths that are selectively absorbed into the substance are characteristic of its component molecules. Then a spectrophotometer measures the light intensities, which yields a way to identify different types of substances.
What are the racial differences in Caucasian hair?
Caucasian Hair Straight or wavy Sparse to dense pigments Fine to coarse evenly distributed pigments Cross-sections = oval (more oval more wavy)
What type of chemical testing can aid in determining the fiber of a fabric?
Chemical testing--solubility and decomposition
What is the class characteristics of sand?
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
What would be a class characteristic of soil evidence?
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
What type of microscopic observation can be made of fibers when seeking to identify them?
Color--compositional differences in the dyes Fibers surface--delustering particles that may be added by manufacturers
What is a concentric fracture pattern?
Concentric—circular lines around the point of impact; begins on
What is density?
Density is the mass of object divided by the volume of the object
How does one test the refractive index of glass?
Density= mass divided by volume Refractive index--the bending of light waves due to a change in velocity. Fractures Color Thickness Fluorescence Markings--striations, dimples, etc
What are the physical characteristics of glass?
Density= mass divided by volume Refractive index--the bending of light waves due to a change in velocity. Fractures Color Thickness Fluorescence Markings--striations, dimples, etc
What are fabrics made of?
Fabrics are made of fibers and fibers are made of twisted filaments Types Natural— Artificial—
What is fluorescence?
Fluorescence--used for comparing fibers of a common origin, as well as spotting fibers for collection
What is forensic botany?
Forensic botany is the study of plant material and relationship to crime scene investigation The significance of plant material at the scene: 1) plant remains can be found almost everywhere 2) offers macroscopic and microscopic evidence, such as pieces of wood, (even as charcoal), seeds, fruits, leaves, twigs, plant hairs, microscopic air-borne pollen and spores, or in aquatic environments, algal cells 3) structure allows identification of the plant and allows gathering of other useful information such as the season or geographical location in which a crime took place, whether a body has been moved following a murder; if a body is buried, how long it has been buried, and whether a suspect was present at the crime scene.
What is forensic geology?
Forensic geology is the application of earth science to the law based on the Locard Principle of transfer-In Forensic science, Locard's exchange principle (sometimes simply Locard's principle) holds that the perpetrator of a crime will bring something into the crime scene and leave with something from it, and that both can be used as forensic evidence. Locard was actually a doctor and lawyer sample earthen materials that have been transferred between objects and analyze for origins or sources
What are fossils and how can they be used in a forensic science analysis?
Fossils are the remains of plants and animals Help geologists to determine age of rock Some are scarce and can be used to identify regions or locations
What Fourier Transform Infrared analysis (_______) and how does it aid in the identification of fabrics?
Fourier Transform Infrared Spectroscopy, also known as FTIR Analysis or FTIR Spectroscopy, is an analytical technique used to identify organic, polymeric, and in some cases, inorganic materials. The FTIR analysis method uses infrared light to scan test samples and observe chemical properties.
Can the sex of a person be determined from a hair strand?
Gender CANNOT be determined by hair (sex can be determined by DNA analysis if root tissue is present).
What is a Glass Refractive Index Measurement?
Glass Refractive Index Measurement--is a computer attached to a video system that views the glass fragments as heat is applied to the liquid medium in a hot stage. The match point temperature is converted to a refractive index using data from the computer.
When can hair be considered evidence of an individual characteristic?
Hair can only be an individual characteristic if DNA is available.
If a detective finds a hair root with follicular tissue attached, what might that indicate?
Hair root with follicular tissue may indicate hair was pulled out forcibly- by a person or comb, etc.
What are the characteristics of glass?
Hard, amorphous material Usually transparent Primarily composed of silica with various amounts of element oxides Brittle Exhibits conchoidal fracture-An irregularly curved and striated surface where there has been a crack.
What can be learned from hair left at a crime scene?
Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime. It can provide a link between the criminal and the act. From hair one can determine: Human or animal Race Origin Manner in which hair was removed Treated hair Drugs ingested
What is the individual characteristic of sand?
Individual characteristic--only if the sand has an unusual characteristic
What would be an individual characteristic of soil evidence?
Individual characteristic--only if the soil has an unusual characteristic such as pollen, seeds, vegetation, or fragments.
What is laminated glass?
Laminated--used in the windshield of most cars
What is the probative value of physical evidence?
Legally, probative value is the level at which evidence provides proof of the crime.
What are the different types of natural fibers in fabric?
Natural Silk Cotton Wool Mohair Cashmere
What are the racial differences in negroid hair?
Negroid Hair Hair shaft and cuticle Irregular in diameter. Dense, unevenly distributed pigment Opaque hair shaft Cross-sections = flat to oval
What is optical microscopy?
Optical microscopy--uses polarizing light and comparison microscopes
When can glass be used as an individual and as a class characteristic of evidence?
Physical evidence can be divided into two categories: Class characteristics are based on similar characteristics that are common within a group, but cannot be linked to a particular individual. Still, evidence with class characteristics can be useful. Recovering several kinds of evidence—such as hair, fiber, and glass fragments—may significantly increase the probability of linking a suspect or victim to a crime scene. Individual characteristics, when present, may allow the forensic examiner to link the evidence to a specific source.
What are the different types of synthetic fibers in fabric?
Polyester Rayon Nylon Acetate Acrylic Spandex
What is Pyrolysis gas chromatography-mass spectrometry (PGC-MS)?
Pyrolysis gas chromatography -mass spectrometry (PGC-MS)--burns a sample under controlled conditions and separates and analyzes each combustion product
What is the 3R rule?
Radial cracks form a Right angle on the Reverse side of the force.
What is 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.
What was the holding in the 1923 decision Fyre v. the United States?
Scientific evidence is allowed into the courtroom if it was generally accepted by the scientific community
What is silica glass?
Silica--used in chemical ware
What is soda glass?
Soda-Line glass It is made of lime. It is used in plate and window glass, glass containers, and electric light bulbs Soda-lead--fine tableware and art objects
What are some characteristics of sand?
Some of the characteristics of sand include? Composition is based material of the source; also gives the sand its color Texture is determined by the way the source was transported Grain size Shape Sorting
What is tempered glass?
Tempered--used in side windows of cars
What is the The Becke Line?
The Becke line "halo" can be seen on the inside of the glass in the slide on the right, indicating that the glass has a higher refractive index than the liquid medium. The Becke line can be seen on the outside of the glass, indicating just the opposite.
What was the first case solved using a neutron activation analysis of hair in the deceased's hand?
The first case was in 1958. Sixteen year old Gaetane Bouchard of Canada was murdered. She had strands of hair in her hand that were later matched to her boyfriend with a ratio of sulfur radiation to phosporous.
What is the follicle ?
The follicle of the hair is the structure from which the hair grows
What is the hair cuticle?
The hair cuticle is the scale structure covering the exterior of the hair_
If the hair cross section is oval, is the hair straight, kinky or curly?
The hair shape is curly.
If the hair cross sections is a crescent moon, is the hair straight, kinky or curly?
The hair shape is kinky.
If the hair cross section is round, is the hair straight, kinky, or curly?
The hair shape is straight.
What is the probative value of soil?
The number of kinds of earth material is virtually unlimited. They have a wide distribution and change rapidly over short distances. As a result, the statistical probability of a given sample having properties similar to another is very small Evidential value of soil is usually excellent
What is the product rule?
The product rule is a formula for determining how frequently a certain combination of characteristics occurs in a population.
What is the root of the hair?
The root of the hair lies below the epidermis
What is the shaft ?
The shaft is the part of the hair that sticks out of the skin
What is palynology?
The study of palynomorphs, or pollen data, trapped in or found on materials associated with a crime. Important to know: What is produced in a given area The dispersal pattern Because of their predictable production and dispersal rates in specific regions, they can help to link a suspect to the scene of a crime.
What is trace evidence?
Trace Evidence--any small pieces of material, man-made or naturally occurring (animal, plant or mineral) These include hair, fibers, glass, soil, sand, plant material The main point is that some apparently foreign object or piece of material is present at a crime scene and tracing its origin can assist in an arrest and conviction. Similarly, finding some trace from the victim or crime scene on a suspect can have a strong impact on a case.
What are the test questions for trace evidence?
What is it? Is it man-made or natural? What is its source? How common is it? Can it be identified to a single source?
What is the medulla?
a cellular column running through the center of the hair, middle of hair, not always present in humans, and can be used to tell different species of animals apart, comes in both types and patterns
What is thermal decomposition?
gently heating to break down the fabric to their monomers
