CJFS 3410 Quiz 2 (Ch. 2)

Questions and Answers

What are the differences between class and individual characteristics of evidence?

Class characteristics allow an item to be compared with a group and are useful for elimination, while individual characteristics can be compared to a specific item and are useful for identification.

Which method for DNA analysis is best for individualization in forensic work and why?

STR is the best method because it produces full profiles from small, degraded samples and is highly discriminating.

How is tape used to collect hair and fiber evidence at the crime scene?

Adhesive tape is applied to an area to lift fibers and is affixed to a transparent backer.

When evaluating glass fractures for direction of force, which fragments can be used?

Primary radial fragments. Signup and view all the answers

How is paint layering used to differentiate two paint samples?

By examining the sequence and number of layers of primers, base coats, and clear coats. Signup and view all the answers

Which environmental variations are significant when comparing soil samples?

Pollen and minerals. Signup and view all the answers

How does evaluating evidence involving a pistol differ from that involving a revolver?

A pistol requires searching for ejected casings, while revolver casings remain in the cylinder. Signup and view all the answers

What two manufactured components of a barrel does rifling refer to?

Lands and grooves. Signup and view all the answers

How are bullets marked for evidence and packaged?

Bullets are marked with item numbers and packaged individually to prevent movement. Signup and view all the answers

Which method of collecting tool mark evidence is better and why?

Collection of the entire item is better because it preserves microscopic characteristics. Signup and view all the answers

What is the most significant class characteristic in shoe mark examinations?

Tread design. Signup and view all the answers

What type of containers are used to collect fire scene evidence with suspected accelerants?

Clean, unlined paint cans or glass jars. Signup and view all the answers

What three things must an investigator know before searching for evidence?

What you are searching for, what a crime lab can do with it, and how to collect it best. Signup and view all the answers

What is Locard's Exchange Principle?

Every contact leaves a trace. Signup and view all the answers

How does cross-contamination occur and with what types of evidence?

It results from improper handling and is particularly problematic for trace evidence and DNA. Signup and view all the answers

Describe class characteristics.

Class characteristics allow an item to be compared with a group and may include size and color. Signup and view all the answers

Describe individual characteristics.

Individual characteristics allow an item to be compared to a specific item and result from uniqueness. Signup and view all the answers

What is a mechanical fit/fracture match and is it individual or class evidence?

A mechanical fit is when an item can be associated with a specific source based on its unique fit. Signup and view all the answers

How can fingerprint evidence be used and what types of characteristics are employed?

Fingerprint evidence is used to include or exclude individuals using both individual and class characteristics. Signup and view all the answers

Give examples of a class-level serology test and an individual-level serology test.

Class - ABO blood testing; Individual - STR profiling using nuclear DNA. Signup and view all the answers

What can be discerned from hair evidence?

Hair evidence can distinguish species, general race, and location from the body. Signup and view all the answers

When should hair and fiber evidence be collected?

Hair and fiber evidence should be collected as soon as possible due to its transient nature. Signup and view all the answers

Which technique is quickly replacing microscopic hair comparisons and why?

MtDNA is replacing it because it provides more objective data. Signup and view all the answers

What can be discerned about fibers and what types of characteristics are analyzed?

Fibers can distinguish source and type; class characteristics include source type, and individual characteristics may include manufacturing dye. Signup and view all the answers

Name properties of glass that may be used for comparison.

Type determination, direction of force, sequence of force, color, thickness, and optical properties. Signup and view all the answers

What is the $Rrule?

Ridge lines on radial fractures are at a right angle to the rear. Signup and view all the answers

What characteristics can be used to identify paint, and give examples of class and individual characteristics.

Individual - sequencing of components; Class - color and basic type. Signup and view all the answers

When collecting soil, what is an important consideration?

Depth. Signup and view all the answers

What is gunshot residue and which three elements can be found in it?

Gunshot residue is burned and unburned discharge from a firearm; elements include Sb, Ba, Pb. Signup and view all the answers

Which method can be used on-scene to examine GSR?

Gunshot residue swabbed over suspected bullet holes. Signup and view all the answers

How can GSR be used to reconstruct a bullet's trajectory?

It can make distance determinations between shooter and target. Signup and view all the answers

What objects does firearms analysis analyze?

Guns, casings, bullets, live cartridges. Signup and view all the answers

Name and describe the three types of tool marks.

Striations - contact and sliding; Compression - forcing into soft material; Saw/Drill Marks - often used to obscure serial numbers. Signup and view all the answers

Why can serial numbers on a gun be restored?

Because the area below has been disrupted and chemicals can reveal it. Signup and view all the answers

Name the four types of impression evidence.

Shoe prints, tire tracks, plastic fingerprints, bite marks. Signup and view all the answers

What two things need to occur during bite mark collection?

Good photos with a scale must be taken, and the bite mark should be swabbed for DNA. Signup and view all the answers

What types of chemical evidence may be found at a crime scene and which instruments are used to analyze them?

Toxins, contaminants, accelerants, drugs. Instruments: GC, MS, IR. Signup and view all the answers

What should document evidence be packaged in?

Paper envelopes. Signup and view all the answers

If suspected writing is found in a tablet, how should it be collected?

Collect the whole tablet. Signup and view all the answers

How should indented writing evidence be packaged?

Between two hard cardboard cutouts. Signup and view all the answers

What should be considered when collecting computer evidence?

Whether the machine is on/off and photograph before dismantling. Signup and view all the answers

What does the ME determine and what information do they use?

They study injuries, determine COD and MOD using medical and scene context. Signup and view all the answers

When does evidence collection occur?

After all scene documentation has been completed. Signup and view all the answers

What information should be included on the label of an item of evidence?

Case #, item description, location, collector's name, etc. Signup and view all the answers

What two types of photos should be taken of evidence?

Comparison photo with scale and mid-range photo to show item position. Signup and view all the answers

Study Notes

Class and Individual Evidence

Class characteristics allow for comparison among a group and are used for elimination.
Individual characteristics link evidence to a specific item or person, enabling inclusion or exclusion.

DNA Analysis

Short Tandem Repeat (STR) method is preferred for individualization due to its ability to generate profiles from small, degraded samples.
STR analysis has a discrimination power of 1 in 6 billion.

Hair and Fiber Collection

Tape is used to lift fibers from surfaces, applied to an area until tackiness decreases.
Samples should be labeled and stored in individual envelopes for proper tracking.

Glass Fractures

Primary radial fragments are useful for evaluating the direction of force in glass fractures.

Paint Layering

The sequence and number of paint layers (e.g., primers, base coats) help differentiate paint samples in forensic comparisons.

Soil Sample Comparison

Soil sample variations include pollen and mineral content, which are significant for comparison.

Firearm Evidence Collection

Pistols produce ejected casings that must be collected, while revolvers retain cartridges in the cylinder.

Bullet Evidence

Bullets should be individually packaged to prevent movement, with clear labeling of recovery details.

Tool Mark Evidence

Collecting the entire item is preferable for tool mark evidence due to microscopic characteristics.

Shoe Mark Examinations

Tread design serves as the most significant class characteristic, aiding in shoe brand identification.

Fire Scene Evidence Containers

Collect fire scene evidence in clean, unlined paint cans or glass jars to avoid contamination.

Evidence Search Considerations

Investigators must know the target evidence, laboratory capabilities, and optimal collection methods before searching.

Locard's Exchange Principle

This principle indicates that every contact leaves a trace, emphasizing its role in forensic evidence.

Cross Contamination Risks

Occurs due to improper handling, significantly affecting trace evidence, DNA, fingerprints, and biological fluids.

Characteristics of Evidence

Class characteristics include common traits across items, while individual characteristics arise from unique traits, such as damage.

Mechanical Fits

A mechanical fit connects items based on how they fit together, serving as individual evidence.

Fingerprint Evidence Usage

Fingerprints help to either include or exclude individuals and consist of both class and individual characteristics.

Serology Testing Examples

Class serology test: ABO blood typing.
Individual serology test: STR profiling using nuclear DNA.

Hair Evidence Insights

Hair can provide information like species, race, and body location but is often class evidence, unless unique dye jobs are present.

Timeliness in Evidence Collection

Hair and fiber evidence can be lost quickly; collection should be immediate, even before scene documentation.

Modern Hair Comparison Methods

Mitochondrial DNA (mtDNA) analysis is replacing microscopic hair comparisons for more objective results.

Fiber Evidence Analysis

Fibers can indicate source types (natural, synthetic) and can provide class and individual characteristics with SEM analysis.

Glass Properties for Comparison

Properties include type, direction of force, visual characteristics (color, thickness), and optics (refractive index).

$R Rule of Glass Fractures

Ridge lines on radial fractures are perpendicular to the rear, aiding in analysis of force applications.

Paint Characteristics

Individual characteristics include layering and sequencing, while class characteristics cover color and type.

Soil Collection Considerations

Soil depth is crucial for meaningful comparison of samples.

Gunshot Residue (GSR)

GSR contains burned and unburned discharge and elements such as Antimony (Sb), Barium (Ba), and Lead (Pb).

GSR Examination on Scene

GSR can be examined by swabbing around suspected bullet holes for analysis.

GSR and Bullet Trajectory

GSR helps determine distances between shooter and target, contributing to trajectory analysis.

Firearm Analysis Components

Analysis involves guns, casings, bullets, and live cartridges.

Types of Toolmarks

Striations occur from contact with a surface, compression marks result from tools pressing into materials, and saw/drill marks obscure serial numbers.

Restoring Gun Serial Numbers

Serial numbers can be restored through chemical treatment of disrupted stamping areas.

Types of Impression Evidence

Impression evidence includes shoe prints, tire tracks, plastic fingerprints, and bite marks.

Bitemark Collection Essentials

Collection involves taking quality photographs with a scale and swabbing for DNA.

Chemical Evidence at Crime Scenes

Common types include toxins, accelerants, and unknown substances, analyzed using techniques like gas chromatography (GC) and mass spectrometry (MS).

Document Evidence Packaging

Paper envelopes should be used for packaging document evidence to prevent damage.

Collecting Suspected Writing

The entire tablet containing suspected writing should be collected for analysis.

Packaging Indented Writing Evidence

Indented writing evidence requires careful packaging between hard cardboard to preserve impressions.

Computer Evidence Collection Considerations

Assess the machine's status (on/off), photograph the setup, and label cables before disassembly for analysis.

Medical Examiner's Role

Determines cause and manner of death (COD/MOD) by studying injuries and crime scene context.

Evidence Collection Timing

Collection occurs post-scene documentation to ensure proper protocol is followed.

Evidence Labeling Details

Labels must include case number, item description, collection details, and any biohazard indicators.

Types of Evidence Photos

Comparison photos with scales and mid-range photos contextualizing the item within the scene are essential for documentation.

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Description

This quiz focuses on the differences between class and individual characteristics of evidence in criminal justice. Understanding these concepts is crucial for effective investigation strategies. Test your knowledge and solidify your understanding of forensic analysis.