Questions and Answers
Describe the differences between class and individual characteristics of evidence.
Class characteristics allow the item to be compared with a group, useful for eliminating possibilities. Individual characteristics allow comparison with a specific object or person, unique due to natural variation, damage, or wear.
What is Locard's Principle of Exchange?
Every contact leaves its trace.
What is mechanical fit?
Fracture matching where the fracture site can be lined up with the other side and individualized based on the fracture line.
What are latent prints?
Signup and view all the answers
What are patent prints?
Signup and view all the answers
What are plastic prints?
Signup and view all the answers
Which method for DNA analysis is best for individualization in forensic work?
Signup and view all the answers
What is Carl Sagan's famous adage about evidence?
Signup and view all the answers
What is the significance of mitochondrial DNA?
Signup and view all the answers
How can hairs be distinguished?
Signup and view all the answers
How are fibers classified?
Signup and view all the answers
What is the loss rate of transferred hairs or fibers after contact?
Signup and view all the answers
How is tape used to collect hair and fiber evidence?
Signup and view all the answers
What are the basic things glass is examined for?
Signup and view all the answers
What is the 4R rule?
Signup and view all the answers
Which fragments can be used to evaluate glass fractures for direction of force?
Signup and view all the answers
What are radial fractures?
Signup and view all the answers
What are concentric fractures?
Signup and view all the answers
How is paint layering used in forensic analysis?
Signup and view all the answers
What factors lead to environmental variations in soil samples?
Signup and view all the answers
What does firearms evidence consist of?
Signup and view all the answers
What is stippling?
Signup and view all the answers
What comprises typical ammunition anatomy?
Signup and view all the answers
What makes up shotgun cartridge anatomy?
Signup and view all the answers
How does evaluating crime scene evidence differ between a pistol and a revolver?
Signup and view all the answers
What do rifling projections and depressions refer to?
Signup and view all the answers
What are bullet types based on firing mechanisms?
Signup and view all the answers
What are fire arm class characteristics?
Signup and view all the answers
How should bullets be marked for evidence?
Signup and view all the answers
What do firearm individual characteristics arise from?
Signup and view all the answers
Which is the better method for collecting tool mark evidence?
Signup and view all the answers
What are tire class characteristics?
Signup and view all the answers
What are tire individual characteristics?
Signup and view all the answers
What is track width?
Signup and view all the answers
What is the most significant class characteristic in shoe mark examinations?
Signup and view all the answers
What type of containers are used to collect fire scene evidence for accelerants?
Signup and view all the answers
What is the difference between forged writing and traced writing?
Signup and view all the answers
What is the appropriate response for collecting a computer for analysis?
Signup and view all the answers
Study Notes
Class vs. Individual Characteristics
- Class characteristics identify a group (e.g., vehicle type) and can eliminate possibilities (e.g., Jeep vs. Honda).
- Individual characteristics are unique to a specific object or person (e.g., fingerprints, wear patterns).
Locard's Principle of Exchange
- Every contact leaves a trace, emphasizing the importance of trace evidence.
Mechanical Fit
- "Fracture matching" technique used to line up fracture sites for individualization based on fracture lines.
Latent Prints
- Invisible fingerprints created by body secretions, not visible to the naked eye.
Patent Prints
- Visible fingerprints caused by contaminants (e.g., grease or blood).
Plastic Prints
- Fingerprint impressions made in soft materials like wax, leaving a three-dimensional print.
DNA Analysis Techniques
- Short tandem repeat (STR) technology is the most effective for individualization in forensic cases, requiring minimal sample sizes.
Absence of Evidence
- Carl Sagan stated, "The absence of evidence is not evidence of absence," highlighting the need for careful evidence interpretation.
Mitochondrial DNA (mDNA)
- mDNA is inherited maternally and is useful in identifying relationships with decomposed bodies, especially with hair samples lacking roots.
Hair Analysis
- Hairs can indicate species and, in human samples, general race and body location; usually classified, can sometimes be individualized.
Fiber Classification
- Fibers are categorized based on their origin: natural, manufactured, or synthetic.
Trace Evidence Loss
- Estimated that 90% of transferred hairs or fibers are lost within the first 8 hours after contact.
Tape Evidence Collection
- Tape is applied to collect hair and fibers, ensuring separate pieces are used for different areas to avoid contamination.
Glass Examination
- Glass analysis includes determining type, direction, and sequence of force; often involves class characteristics.
4R Rule for Glass Fractures
- Ridge lines on radial fractures are perpendicular to the rear of the glass; used for identifying fracture direction.
Paint Sample Differentiation
- Paint layering (primers, base coats, clear coats) helps distinguish samples; proper collection techniques are essential.
Soil Sample Comparison
- Varied environmental factors contribute to soil sample differences; pollen evaluation is a useful comparative method.
Firearms Evidence
- Analysis includes examining weapons and casings for association; distance determinations can be made through gunshot residue (GSR) patterns.
Stippling
- Gunpowder particles embed in skin during close or near-contact wounds, indicating proximity to the shooting.
Ammunition Components
- Cartridges consist of bullets, casings, powder charge, and primers.
Pistol vs. Revolver Evidence Collection
- Revolvers retain casings internally; pistols eject spent casings, affecting evidence collection strategies.
Rifling Characteristics
- Barrel rifling consists of lands (projections) and grooves (depressions) that determine bullet trajectory.
Types of Rifle Shots
- Single-shot, semiautomatic, and automatic denote how ammunition is fed and fired.
Firearm Class Characteristics
- Caliber, barrel shape, firing pin location, and rifling features serve as class characteristics for firearms.
Evidence Marking
- Firearms and bullets should not be directly marked to preserve microscopic details; they must be properly containerized to prevent damage.
Tool Mark Evidence Collection
- Collecting the actual tool mark is preferred over casting for accuracy and value retention.
Tire Characteristics
- Class characteristics: tread design, noise treatment, tread-wear bars; individual characteristics arise from unique wear patterns.
Track Width Measurement
- Defined by measuring the distance between the tracks on the front or rear axle, critical for crime scene analysis.
Shoe Mark Examination
- Tread design serves as a major class characteristic for shoe marks, aiding in suspect identification through databases.
Collecting Fire Scene Evidence
- Accelerants should be collected in unlined paint cans or glass jars to avoid contamination.
Distinction of Forged vs. Traced Writing
- Forgeries mimic known writing to identify the author; tracing involves copying and lacks unique movement, preventing identification.
Collecting Computers for Forensic Analysis
- If a computer is off: document connections, label cables, package securely. If it's on: identify destructive programs and document running processes before collecting.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Explore the key concepts of physical evidence in forensics through these flashcards. Understand the differences between class and individual characteristics, and how these traits help in criminal investigations. Perfect for students looking to grasp essential forensic principles.