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Questions and Answers
What distinguishes forensic chemistry from general chemistry?
Which type of fiber is most likely to be involved in contact between a victim and a suspect?
What is one main characteristic of hair that makes it valuable in forensic investigations?
In terms of composition, how can explosives be classified?
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What part of the hair is considered the most distinctive?
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What type of hair is characterized as generally long and stiff?
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Why is hair considered a significant form of physical evidence?
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Which of the following is NOT a part of hair?
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Which characteristic best describes beard hair?
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What distinguishes axillary hair from pubic hair?
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Why is microscopic testing considered the most reliable method for identifying fibers?
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What is a common characteristic of infant hairs?
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What are the primary classifications of textile fibers?
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Which test is used to determine the general group to which a fiber belongs?
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What is a typical feature of trunk hair?
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Which chemical test involves staining fibers for analysis?
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What is the defining characteristic of wool that distinguishes it from silk and vegetable fibers?
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Which type of fiber is described as being multicellular and tapering to a sharp point?
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What is the purpose of using the dissolution test on fibers?
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Which of the following characteristics describes mercerized cotton?
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What distinguishes wild silk from cultivated silk?
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What is the primary component of gallotannic ink?
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What key aspect is crucial in determining the authenticity of any document?
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Which type of ink is most resistant to washing off from paper?
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Which of the following is NOT a common problem encountered in document examination?
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What type of ink is known for easily smudging and being affected by moisture?
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What is the definition of a document in the context of document examination?
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What is a common characteristic of carbon ink?
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Which of the following types of ink contains potassium dichromate?
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What is the purpose of sizing materials in paper composition?
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Which of the following is NOT a type of fiber composition for paper?
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What is evaluated in the preliminary examination of paper?
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What does the bursting strength test measure?
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Which loading material is used to add weight to paper?
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What is the main goal of the physical examination that causes a perceptible change?
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Which of the following tests determines the rate at which paper absorbs liquid?
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What effect does the accelerated aging test aim to replicate?
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Study Notes
Forensic Chemistry and Toxicology
- Forensic chemistry is the analysis of substances to determine their identity, especially when they might be mistaken or confused.
- Forensic chemists use scientific methods to analyze the physical and chemical properties of materials.
Explosives
- Explosives are substances that cause a rapid decomposition or combustion, leading to an explosion.
- Explosives can be classified based on their chemical composition or functioning characteristics.
Hair and Textile Fibers
- Hair examination is an old method of physical evidence, even older than fingerprints.
- Human and animal hair is unique, making it valuable for forensic analysis.
- Hair can be used to link a suspect or victim to a crime scene because it can transfer between individuals during contact.
- Hair is resistant to decomposition and purification, making it a valuable source of evidence even after other forms of evidence are destroyed.
- Hair is a specialized epithelial outgrowth of the skin, found on all parts of the body except the palms of the hands and soles of the feet.
- Different types of hair include real hair, fuzz hair, beard hair, hair from eyebrows, eyelids, nose, and ears, trunk hair, limb hair, axillary hair, and pubic hair.
- Each type of hair has unique characteristics in terms of texture, shape, and pigmentation.
Textile Fibers
- Textile fibers are fibers that can be converted into yarn.
- Yarn is made from fibers twisted together.
- Textile fibers can be classified into natural fibers and synthetic or artificial fibers.
Tests for Fibers
- Burning test: Determines if a fiber is mineral, animal, or vegetable.
- Fluorescence test: Used for general fiber grouping.
- Microscopic test: The most reliable method for fiber identification.
- Chemical test: Used for fiber analysis depending on the specific fiber type.
Chemical Tests for Fibers
- Staining test: Uses dyes like picric acid, million's reagent, stannic chloride, or iodine solution to stain fibers.
- Dissolution test: Uses various chemicals like NaOH, oxalic acid, and ammonia to dissolve fibers.
Characteristics of Common Textile Fibers
- Cotton: Unicellular, flat, ribbon-like, twisted spirally.
- Mercerized cotton: Straight, cylindrical, unevenly lustrous, smooth with slight transverse folds or wrinkles.
- Linen: Multicellular, straight, cylindrical, flattened, tapering to a sharp point.
- Cultivated silk: Smooth, cylindrical, lustrous, single or double filaments held together by gum.
- Wild silk: Similar to cultivated silk but broader and less regular.
- Artificial silk: Cylindrical, lustrous, resembling a glass rod.
- Wool: Flattened, overlapping epidermal scales not found in silk or vegetable fibers.
Questioned Documents
- A questioned document is any object containing handwritten or typewritten markings whose source or authenticity is in doubt.
- Document examination focuses on the paper and ink used to create the document.
- Paper examination can determine the age of the document, presence of alterations, erasures, and other forms of forgery.
Problems Encountered in Document Examination
- Determining if two pieces of paper originated from the same source.
- Estimating the age of the paper.
- Analyzing the composition of the paper.
Egyptian Papyrus
- One of the earliest writing materials, derived from the papyrus plant.
- The word "paper" comes from "papyrus."
Composition of Paper
- Fiber composition: Mechanical pulp, soda-sulfate mixture, and rag sulfate.
- Sizing material: Improves paper quality and texture (e.g., rosin, casein, gelatin, starch).
- Loading material: Adds weight to the paper and fills pores between fibers (e.g., calcium sulfate, barium sulfate).
Four Tests of Paper
- Preliminary examination: Observes appearance, folds, creases, odor, transmitted light impression, and discoloration.
- Physical test without perceptible change: Measures length, width, thickness, weight per area, color, texture, gloss, conducts microscopic examination, and determines opacity.
- Physical test with perceptible change: Requires samples and court authorization.
- Bursting strength test: Measures the force required to burst a hole in the paper.
- Folding endurance test: Measures the number of folds a paper can withstand before breaking.
- Accelerated aging test: Artificially ages documents.
- Absorption test: Measures the rate of absorption of the paper.
- Chemical test: Identifies the fiber composition, loading material, and sizing material used in the paper.
Ink
- Ink analysis investigates the type of ink used, whether inks are alike or different, and the age of the ink.
Types of Ink
- Gallotannic Ink (Iron Ink): Most common ink used for records and business.
- Logwood ink: Inexpensive, does not corrode steel pens.
- Negrosine ink (Aniline ink): Made of coal tar products, smudges easily and can be washed off.
- Carbon ink (Chinese ink or India ink): Oldest ink material, does not penetrate deeply into the paper, can be easily washed off.
- Colored writing ink: Composed of synthetic aniline dyestuffs, more permanent.
- Ballpoint ink: Composed of light-fast dyes soluble in glycol solvents.
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Description
Test your knowledge on the analysis of substances in forensic chemistry, the properties of explosives, and the significance of hair and textile fibers in forensic investigations. This quiz covers essential concepts and applications in forensic science.
