Forensic Science Exam Study Guide
FS 11 – Survey of Forensic Science Exam 1 Study Guide
1. Intended Purposes
The intended purpose of science is to explore and understand phenomena through systematic observation, experimentation, and theoretical explanations.
The intended purpose of law is to establish regulations and standards to govern behavior and ensure justice within society.
2. Definition of Forensic Science
Forensic science is the application of scientific principles and techniques to solve crimes and analyze physical evidence.
The word forensis is derived from Latin, meaning "of the forum," which refers to the public place where judicial proceedings and discussions took place.
3. Historical Findings of Forensic Applications in China
Two historical findings that demonstrate early forensic-like applications in China include:
Use of bloodstain analysis to identify causes of death during the Song Dynasty.
Employment of fingerprinting techniques as a means of identification in ancient Chinese law.
4. First Known Autopsy
The first known autopsy was performed on a historical figure named Aristotle, who studied the anatomy of animals, paving the way for the practice of autopsies in humans.
5. Sir Arthur Conan Doyle
Sir Arthur Conan Doyle was a British author and creator of the character Sherlock Holmes, known for using logic and scientific methods to solve crimes.
His impact on forensic science includes inspiring law enforcement and forensic investigators to apply scientific reasoning and investigation techniques in real-world cases.
6. Contributions to Forensic Science
Victor Balthazard: Pioneered techniques for analyzing hair and fingerprints.
Sir Francis Galton: Developed fingerprint classification and analyzed individual uniqueness in fingerprints.
Hans Gross: Founded the field of criminalistics and emphasized scientific methods in investigations.
Edmond Locard: Formulated Locard's Exchange Principle, stating that every contact leaves a trace.
Mathieu Orfila: Considered the father of toxicology; advanced the study of poisons in medicine and law.
7. Goals of Forensic Investigations
Identify: Recognizing the individuals involved in a crime.
Establish: Determining the sequence of events in a crime.
Support: Providing scientific evidence to support or refute claims in legal contexts.
8. Rapid Growth of Crime Labs in the U.S.
Two reasons for the rapid growth in the number of crime labs across the U.S. include:
Increasing crime rates and the complexity of crimes.
Advancements in technology have increased the capabilities and demands of forensic sciences.
9. Federal Laboratories Conducting Forensics
The five federal laboratories run by the government that involve forensics include:
Federal Bureau of Investigation (FBI) Laboratory.
Drug Enforcement Administration (DEA) Laboratory.
Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) Laboratory.
U.S. Secret Service Laboratory.
Department of Defense (DOD) Laboratory.
10. Personal Protective Equipment (PPE)
PPE stands for Personal Protective Equipment. It consists of gear designed to protect the wearer from physical injuries or hazardous materials. Examples include gloves, goggles, face shields, and protective clothing.
11. Differences in Forensic Specializations
Forensic specialists vs. generalists:
Forensic specialists possess expertise in specific areas (e.g., toxicology, DNA analysis), whereas forensic generalists have a broader understanding of various forensic disciplines.
Public vs. private laboratories:
Public laboratories are government-funded and focused on criminal cases. Private laboratories operate independently, often serving private clients or corporations.
12. Steps for Processing Evidence
The seven steps that a forensic scientist follows when processing evidence are:
Recognition of Evidence: Identifying what items may be relevant to a case.
Documenting: Recording the evidence through notes, sketches, and photographs.
Four major tasks of documentation:
Taking detailed notes, creating sketches, capturing photographs, and creating a timeline of events.
Collection: Physically gathering the evidence.
Packing: Properly storing evidence to prevent contamination.
Preservation: Ensuring evidence is kept safe and secure.
Analysis: Conducting forensic tests to evaluate the evidence.
Presentation in Court: Sharing findings through reports or testimony in legal proceedings.
Basic approach to photographing a crime scene:
Use a scale for size reference, take multiple angles, and capture overall views before moving or altering the scene.
13. Search Patterns
Four types of search patterns employed in crime scene investigations include:
Grid Search: Systematic line search in overlapping lanes.
Zone Search: Dividing area into sections and inspecting each.
Spiral Search: Starting from an inner point and moving outward in a spiral.
Line Search: Searchers line up and move in a straight line.
14. Forensic Investigative Team Members
The six groups of individuals that make up the forensic investigative team include:
Police Officers: First responders, secure the scene.
Crime Scene Investigators (CSIs): Collect evidence and document the scene.
Forensic Scientists: Analyze evidence collected.
Medical Examiners/Coroners: Determine cause of death.
Prosecutors: Represent the state in court.
Defense Attorneys: Represent defendants in legal matters.
15. Chain of Custody
The chain of custody is a process that ensures the evidence collected is preserved and is trusted for presentation in court.
A chain of custody evidence log contains:
Date/time of collection, description of the evidence, names of individuals who handled the evidence, and any transfers or changes in custody.
16. Locard’s Principle
Locard’s Principle states that “Every contact leaves a trace,” meaning any interaction between a suspect and a crime scene results in the transfer of material.
17. Definition of Evidence
Evidence is any object or information that is used to prove or disprove a fact in a court of law.
18. Physical Evidence
Physical evidence is tangible items that can be observed and analyzed. There are two types of physical evidence:
Real Evidence: Directly tied to the crime, such as fingerprints or weapons.
Demonstrative Evidence: Used to illustrate or explain evidence, like photographs or diagrams.
19. Classifying Physical Evidence
Physical evidence can be classified as either class evidence (indicating a general group or category, e.g., clothing fibers) or individual evidence (unique to a particular source, e.g., a fingerprint). Examples include:
Class: A red thread from a sweater.
Individual: A specific bullet that matches a gun.
20. Biological Evidence
Biological evidence refers to any items that originate from a living organism. Three examples include:
Blood, fingerprints, and hair.
21. Guidelines for Evidence Collection
Guidelines for collecting, packing, and preserving evidence include:
Wear PPE, use appropriate containers, avoid contamination, and maintain a clear chain of custody.
22. Law of Evidence
The law of evidence states guidelines governing the admissibility and presentation of evidence in court proceedings.
23. Admissibility of Evidence in Court
For evidence to be admissible in court, it must meet two requirements:
Relevance: Evidence must pertain to the case.
Reliability: Evidence must be proven to be credible and accepted by the scientific community.
The judge determines the admissibility of evidence in court.
24. Will West Case
The Will West case involved the first use of fingerprinting to prove identity—a man was wrongly imprisoned due to a name similarity until fingerprints differentiated him from another individual.
25. Accreditation vs. Creditations
Accreditation: A formal recognition that an organization meets specific quality standards.
Creditation: Term generally refers to the acknowledgment of educational qualifications or competencies but is less commonly used concerning forensic labs compared to accreditation.
26. Forensic Serology
Forensic serology is the study of blood and other bodily fluids with the aim of identifying and analyzing their characteristics.
27. Components of the Cardiovascular System
Major components of the cardiovascular system include the heart, blood vessels (arteries, veins, capillaries), and blood.
28. Main Components of Blood
The main components of blood include:
Plasma (55%): Fluid portion carrying nutrients, hormones, and proteins.
Red Blood Cells (RBCs, 40-45%): Carry oxygen.
White Blood Cells (WBCs, <1%): Immune response.
Platelets (<1%): Help in blood clotting.
29. Cellular Components of Blood
The three cellular components of blood are:
Red Blood Cells: Lack a nucleus.
White Blood Cells: Contain a nucleus and play immune roles.
Platelets: Cell fragments involved in clotting.
30. Aspects of Crime Informed by Bloodstains
Four aspects bloodstains can inform forensic investigators about include:
Source: Identifying the type of blood (human or animal).
Type of Crime: Nature of the crime, e.g., homicide, assault.
Position of Victim: Where the victim was standing or lying.
Movement: Directions and speed of movements during the incident.
31. Doctor Discovering the A-B-O Blood System
The doctor who discovered the A-B-O blood system was Karl Landsteiner. His discovery was prompted by the need to prevent blood transfusion reactions, leading to safe blood transfusion protocols.
32. Presumptive and Confirmatory Tests
Presumptive Tests: Indicate the presence of a substance but do not confirm it; examples include the Kastle-Meyer test for blood and Luminol testing for blood traces.
Confirmatory Tests: Provide definitive identification of a substance; examples include blood typing and DNA testing.
Issue with presumptive tests: They may yield false positives or may not identify the specific type of material.
33. Shape of Blood Droplets
Blood droplets when separated from their source form spherical shapes. Factors affecting the shape include height and surface texture.
As height increases, the diameter of blood droplets also increases.
The name of the surface area that blood falls on is referred to as a target surface.
Different surface textures can alter the spatter shape; e.g., smooth vs. rough surfaces may lead to different patterns.
Small droplets found around a parent stain are called satellite stains.
With increased velocity of impact, the blood droplet size decreases.
As the angle of impact decreases, the shape of the blood droplet becomes elongated.
34. Calculating the Angle of Impact
The equation for calculating the angle of impact is given by: where is the angle, is the width of the stain, and is the length.
The angle of impact can be used to determine the position and movement of individuals involved in a crime.
35. DNA and RNA Definitions
DNA: Deoxyribonucleic Acid, the molecule that contains genetic information.
RNA: Ribonucleic Acid, a molecule involved in genetic coding, decoding, regulation, and expression.
36. Smallest Subunit of DNA
The smallest subunit of DNA is known as a nucleotide.
37. Composition of Nucleotides
Nucleotides are made of three components:
A phosphate group
A five-carbon sugar (deoxyribose in DNA)
A nitrogenous base (Adenine, Thymine, Cytosine, Guanine).
The five nucleotides are:
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Uracil (U - in RNA).
Nucleotides that pair to form complementary base pairs include:
Adenine pairs with Thymine, and Guanine pairs with Cytosine.
38. Force Holding DNA Strands Together
The force that holds the two strands of DNA together is hydrogen bonding. The two strands run in opposite directions, which is referred to as antiparallel.
39. Images of DNA Scientists
The two scientists known for producing images of DNA are Rosalind Franklin and Maurice Wilkins. The analytical instrument used was the X-ray diffraction technique.
40. Determine DNA's Structure and Replication
The two scientists who determined the molecular shape of DNA and its method of replication are James Watson and Francis Crick.
41. Contributions of Sir Alec Jeffreys
Sir Alec Jeffreys is known for developing techniques for DNA fingerprinting, which enables individual identification based on unique genetic profiles.
42. Structure Representing Organized DNA
The tightly coiled, thread-like structure that represents organized DNA is called a chromosome.
This structure contains genes, which are sequences of DNA responsible for hereditary traits.
43. Definitions of Genetic Terms
Genes: Segments of DNA that code for proteins.
Loci: Specific locations on a chromosome where genes are found.
Alleles: Variants of a gene that may produce differing traits. A progeny inherits two alleles for each gene—one from each parent.
44. Genotype vs. Phenotype
Genotype: The genetic makeup of an organism.
Phenotype: The observable physical or biochemical characteristics of an organism, influenced by genotype and environment.
45. DNA Function
DNA codes for making proteins, including enzymes, hormones, and structural proteins. Examples include hemoglobin and collagen.
46. Non-Coding Regions of DNA
Non-coding regions of DNA are segments that do not code for proteins but may have regulatory or unknown functions in the genome.
47. Sources of DNA
Five examples of DNA sources include:
Blood, saliva, hair, skin cells, and bone.
48. Short Tandem Repeats (STRs)
STR stands for Short Tandem Repeats. They are located on specific regions of chromosomes and assist in forensic DNA profiling by serving as markers for individual identification.
49. Forensic Analyses of DNA Processes
The first step involved in retrieving DNA is sample collection, which involves acquiring biological specimens.
PCR stands for Polymerase Chain Reaction. It serves to amplify DNA, making it easier to analyze. This method is crucial for generating DNA profiles from limited samples like bodily fluids. PCR works through a sequence of denaturation, annealing, and extension.
Electrophoresis is a technique used to separate DNA fragments based on size through a gel matrix.
50. CODIS
CODIS stands for Combined DNA Index System. Its purpose is to store and compare DNA profiles from crime scenes, offenders, and missing persons. The index utilizes 20 loci for DNA analysis.
51. Forensic Value of Genetic Profile
To be of forensic value, a genetic profile must demonstrate individual uniqueness, which is known as individualization.
52. Mitochondria
Mitochondria are organelles within cells that produce energy.
Compared to nuclear DNA, mitochondrial DNA is circular and contains fewer genes; it is located in the cytoplasm of cells. Mitochondria contain 37 genes and are inherited maternally.
53. Y-STRs
A Y-STR is a Y-chromosome Short Tandem Repeat, which is inherited from the male parent. Y-STRs are useful in forensic investigations for tracing paternal lineage.
54. Areas of the Body Lacking Hair
The three areas of the body that do not contain hair are the palms of hands, soles of feet, and certain mucous membranes; these regions are known as glabrous skin.
55. Category of Physical Evidence for Hair
Hair is classified as biological evidence. Forensic characteristics hair represents include species identification and potential origin of hair (e.g., human vs. animal).
56. Associative Evidence
Associative evidence refers to items that link a suspect to a crime scene (e.g., hair or fibers found on a suspect that match those found at the scene).
57. Information Provided by Hair Evidence
Hair can indicate biological traits such as race or health; however, it generally cannot provide definitive identification of an individual unless accompanied by DNA analysis.
58. Hair Morphology
Keratin: A fibrous protein that forms the structure of hair.
The structure that produces hair is known as the hair follicle.
The component responsible for hair color is melanin.
The dermal papilla provides nutrients to the hair follicle.
The sebaceous gland produces sebum, which lubricates and waterproofs hair.
The three layers of hair include:
Cuticle: Outer layer, protective and translucent.
Cortex: Middle layer, contains the majority of hair's pigment and strength.
Medulla: Innermost layer, not always present, may be continuous or fragmented.
59. Medullary Ratio
The medullary ratio is the comparison of the diameter of the medulla to that of the entire hair shaft; it can reveal the origin of the hair (e.g., animal vs. human).
60. Structural Features to Differentiate Hair Types
Two structural features useful for distinguishing animal hair from human hair include:
Medullary pattern (animals have a more prominent medulla)
Cuticle scale patterns differ between species.
61. Developmental Phases of Hair
The three developmental phases of hair are:
Anagen: Growth phase, hair is actively growing.
Catagen: Transitional phase, hair stops growing and begins to shrink.
Telogen: Resting phase, hair is shed.
62. Hair Collection Methods
Two methods of collection for hair include tweezers and scissors. Strands should be packaged individually to prevent cross-contamination and allow for accurate analysis.
63. Reference Samples of Hair Collection
Reference samples of hair from a suspect are typically collected from the crown of the head or other areas of the body that could match the evidence.
64. Definition and Importance of Fibers
A fiber is a basic, elongated material that can be spun into yarn and woven into fabric. Fibers are practical for forensic investigations because they can link suspects to crime scenes.
Fibers can reveal class characteristics such as color and texture.
Stephen Lawrence was a victim of a racially motivated murder; fibers found on his clothing linked a suspect to the crime, resulting in forensic evidence supporting the prosecution.
65. Microscopes for Observing Fibers
A polarizing microscope is typically used to observe fibers under magnification.
66. Types of Fibers
Two categories of fibers include:
Natural Fibers: Derived from plants (e.g., cotton, linen) or animals (e.g., wool, silk).
Synthetic Fibers: Man-made fibers created from polymers (e.g., polyester, nylon).
67. Groups of Yarn
Two groups of yarn include:
Spun Yarn: Made from short fibers twisted together; typically softer and warmer.
Filament Yarn: Composed of long fibers; usually smoother and stronger.
68. Physical Properties of Yarn in Forensics
Five physical properties of yarn used in forensic examinations include:
Color, diameter, texture, twist, and the presence of any distinctive markings or patterns.
69. Categories of Synthetic Fibers
Two categories of synthetic fibers are:
Polyester: Made from PET resin; commonly used in clothing.
Acrylic: Made from polyacrylonitrile; often used in blankets and textiles.
Synthetic fibers are produced through chemical processes that polymerize raw materials. They generally have a more uniform appearance than natural fibers.
70. Initial and Comparison Examination of Fibers
The initial examination of fibers is carried out using a stereo microscope; comparison of a control and questioned fiber is carried out with a comparison microscope.
Advantages of these methods include high magnification for detailed observation and ability to analyze features side-by-side.
One other method used for fiber analysis is Fourier-transform infrared spectroscopy (FTIR).
71. Category of Physical Evidence for Paint
Paint is considered trace evidence, as it can be used to associate suspects with specific locations or items involved in crimes such as burglary or hit-and-run.
72. Types of Paints
There are two types of paints:
Water-based Paints: Use water as the solvent; generally used for interior surfaces.
Oil-based Paints: Use oil or resin as the solvent; typically used for exterior or high durability applications.
73. Main Components of Paint
The three main components of paint include:
Pigments: Provide color and opacity.
Binders: Hold the pigments together and adhere them to surfaces.
Solvents: Dissolve the binder and allow for easy application.
The term ‘emulsion’ refers to a mixture of two immiscible liquids, often seen in paint where water and oil components blend with chemicals to form a stable solution.
74. Layers of Car Paint
The four layers of car paint include:
Primer: Prepares the surface for better adhesion.
Base Coat: Provides color.
Clear Coat: Protects from UV rays and scratches.
Top Coat: Overall protective layer enhancing durability.
75. Collecting Paint Evidence
When collecting paint evidence:
Instruments used may include a scraper, knife, or tweezers.
Reference samples are typically collected from areas in burglaries (e.g., door frames) and from vehicles involved in accidents (e.g., bumpers).
76. Collecting Paint Samples Down to Base
Forensic examiners collect paint samples all the way down to the base of an object to ensure they capture all layers for accurate analysis.
Other items that can be found at crime scenes that may contain paint include furniture or nearby surfaces adjacent to entry points. Items are typically packaged in paper or glass containers for transport.
77. Identifying Paint Evidence
Two ways in which paint evidence is identified include:
Microscopic Analysis: Examining the color, layer structure, and texture.
Chemical Analysis: Testing chemical composition via techniques like FTIR or Gas Chromatography.
78. Definition and Melting Point of Glass
Glass is defined as a transparent or translucent material made from silica (silicon dioxide). Its melting point generally ranges from 1400 °C to 1600 °C, depending on composition.
79. Types of Glass and Properties
The three types of glass include:
Regular Glass: Commonly used in windows; is typically clear and brittle.
Tempered Glass: Increased strength; shatters into small pieces.
Laminated Glass: Layered structure; holds together when shattered.
80. Becke's Line
Becke's line is an optical phenomenon observed during the refractive index matching; seen as a halo effect around the edge of a glass fragment under examination.
81. Glass Fractures Appearance
Radial fractures appear as lines that radiate outward from the point of impact; chonchoidal fractures create smooth-edged, curved surfaces.
82. Appearance of Glass Post-Bullet Impact
When a bullet passes through glass, the side of exit is typically larger and may exhibit distinct fracturing patterns—commonly larger than entry side.
83. Examining a Soil Sample
The first step in examining soil samples involves visual inspection and evaluation of physical characteristics (color, texture, structure).
84. Types of Soil Horizons
The three types of soil horizons include:
O Horizon: Organic layer, composed of decomposing plant material.
A Horizon: Topsoil, rich in nutrients and minerals; supports plant growth.
B Horizon: Subsoil, accumulation of leached materials and minerals from above layers.
85. Soil Color Assessment Code
The standard code used to assess soil color is known as Munsell color system.
86. Difference Between Minerals and Rocks
Minerals are naturally occurring inorganic substances with a defined chemical composition and crystal structure.
Rocks are aggregates composed of one or more minerals or mineraloids, classified based on their formation process—igneous, sedimentary, or metamorphic.