Work Text:
Forensic Science: Pattern Evidence - Comprehensive Notes
04.01 Introduction to Pattern Evidence
Anchoring Case – Ted Bundy
- Location: Western United States, January 1974 - February 1978
- Case involved unsolved assaults and murders in Washington, Utah, and Colorado.
- Initial lack of connections between crimes due to limited information sharing and no internet.
- 1975 Breakthrough: Ted Bundy arrested in Utah for suspicious behavior (items found: ski mask, crowbar, handcuffs), but insufficient for detention.
- Later Arrest: Bundy identified by a surviving victim, became prime suspect for multiple murders.
- Extradition and Escapes: Extradited to Colorado, escaped from courthouse window, recaptured after six days, escaped again, fled to Florida, committed more murders.
- Evidence Found: Witness accounts, weapon marks, fingerprint smudges, blood evidence, bite mark.
- Resource: Fort Collins Coloradoan podcast "Hunted: Inside Ted Bundy's Trail of Terror" (content warning: sensitive material).
- Essential Question: How did evidence collection and examination help solve the Bundy murder cases?
- Unique Evidence: Bite mark linked Bundy to crimes across three states; in Florida, bite mark evidence was critical for death penalty conviction.
Types of Pattern Evidence
- Focus Question: What are examples of pattern evidence?
- Definition: Pattern evidence results from physical contact between an object and a surface (impression).
- Examples:
- Bite Marks: Models compare victim wounds to suspect’s teeth.
- Footprints: Casts of shoe treads in soil/flooring compared to suspect/victim shoes.
- Tire Tracks: Impressions in soil compared to suspect’s vehicle tires.
- Tool Marks: Impressions from weapons/tools compared to suspect’s tools.
- Fingerprints: Photographed/collected for comparison with suspect’s prints.
- Blood Spatter: Patterns indicate mode/force of injury, providing crime scene insights.
- Note: Pattern evidence is often circumstantial, requiring supporting evidence; fingerprints are individual evidence, others are class evidence.
04.02 Casts and Impressions
Ted Bundy Case
- Pivotal Evidence: Bite mark on a victim was key, showcasing forensic odontology.
- Essential Question: How do impressions help forensic scientists?
It's All in the Teeth
- Focus Question: How can teeth impressions be used as evidence?
- Process:
- Swab bite marks for saliva/DNA.
- Steps: Photograph with ruler, take multiple angles, outline tooth marks, identify tooth types, note variations in angle/arrangement.
- Bite Mark Anatomy: Examines dental structure (e.g., molars, incisors); tooth size/structure affects mark appearance.
- Molds: Impression substrate in plastic tray pressed around teeth/gums.
- Casts: Plaster-filled mold creates a teeth replica for crime scene recreation.
- Bundy Case: Crooked incisor matched bite mark perfectly, supported by other evidence; straight teeth less confirmatory due to common dental corrections.
Collecting Impressions
- Focus Question: How are impressions collected from a crime scene?
- Types:
- Patent: Visible, 2D (e.g., visible footprint).
- Latent: Invisible until processed, 2D (e.g., dusted fingerprint).
- Plastic: Visible, 3D (e.g., footprint in mud).
- Methods:
- Photographing: Include ruler, mark measurements relative to other evidence.
- Casting: Use putty/plaster for 3D impressions.
- Electrostatic Dust Lifter: Black plastic film charged to attract dust from footprints, reveals details under blue light.
- Importance: Impressions recreate crime scene marks, match to weapons/suspects, useful as demonstrative evidence in court.
All About Patterns
- Focus Question: How are tire tracks and footprints used as evidence?
- Tire Tracks:
- Influenced by air pressure, speed, vehicle type.
- Traits: Wear pattern, tread depth, speed (well-defined = slow, smudged = fast), tire pattern (matched via database).
- Footprints:
- Traits: Shoe type, gait/path, weight (deeper print = heavier person).
- Trace Evidence: Soil, paint, pollen in treads/footprints provide additional clues.
04.03 Tool Mark Evidence
The MacDonald Family Case
- 1979: Collette MacDonald and two children murdered; Jeffrey MacDonald (husband) survived with minor injuries, claimed intruder responsible.
- Evidence: Knife, bloody splinters, digital fingerprint, bloody footprints, wounds in wife’s chest.
- Essential Question: What are tool marks and how are they used as evidence?
Making Marks
- Focus Question: What information can a tool mark tell a forensic scientist?
- Definition: Tool marks are impressions or material transfers from tools (e.g., hammer, knife) contacting another object.
- Common Tools:
- Pry Bars: Two-prong marks, possible paint transfer.
- Screwdrivers: End bit marks, varies by wear.
- Hammers: Circular marks from head center.
- Chisels: Flat, deep marks.
- Knives: Vary by angle (slice vs. stab), possible blade fragments.
- Razorblades: Thin slit marks.
- Bats: Blunt marks, possible material transfer.
- Bullets: Striations from gun barrel, impact marks identify firearm.
Mark Evidence
- Focus Question: How is tool mark evidence collected?
- Collection Techniques:
- Confirm mark is crime-related.
- Photograph with ruler.
- Collect object with mark or make a cast.
- Record observations on tool use.
- Classification: Class (group of tools) or individual (specific tool) characteristics.
Mark Analysis
- Focus Question: How is tool mark evidence analyzed?
- Process: Compare mark to sample tools via microscope, document details, use databases (NRBTD for tool marks, NIBIN for ballistic evidence).
- Databases:
- NRBTD: NIST’s open-access tool mark database with microscopic/3D images.
- NIBIN: Compares ballistic evidence to find firearm matches.
Review the Case
- MacDonald Case Findings:
- Bloody Footprints: From daughter’s bedroom only, contradicted MacDonald’s story.
- Bloody Splinters: Matched wooden club, found on MacDonald and victims.
- Knife: No fingerprints, blood appeared placed.
- Wounds: Ice pick matched wife’s chest wound, not the knife.
- Key Terms: NIBIN database, NRBTD database, Striations, Tool mark.
04.04 Fingerprints
Burglary Binge
- Location: Panama City, Florida; series of burglaries by one person/group.
- Breakthrough: Digital fingerprint via AFIS database.
- Essential Question: How can fingerprints be used in an investigation?
Fingerprint Basics
- Focus Question: What makes a fingerprint unique?
- Uniqueness: No two people have identical fingerprints, determined by chaotic ridge growth in fetal development.
- Video Insights (Minute Earth):
- Main Pattern: Determined by volar pad size/orientation (arch, loop, whorl, double-loop).
- Uniqueness Source: Chaotic ridge growth influenced by nerve/capillary growth, fluid pressure, finger orientation.
- Factors: DNA, nerve/capillary growth, fluid pressure, gravity.
- Relatives: Share main patterns but not identical due to random ridge details.
- Patterns:
- Arch: 5%, ridges flow in/out opposite sides, 0 deltas.
- Loop: 60%, ridges flow in/out same side, 1 delta.
- Whorl: 35%, circular ridges, 2 deltas.
- Check Understanding: Whorl with two deltas, loops with ridges flowing in/out same side.
Collecting Fingerprints
- Focus Question: How are fingerprints collected?
- Composition: Sweat, skin cells, proteins, fats from sweat glands/pores.
- Types:
- Patent: Visible, 2D (ink, blood, grease); collect via photograph/tape, store in cooler.
- Latent: Invisible until processed (powders, UV, fumes); collect via dusting, photography, electrostatic dust lifter.
- Plastic: Visible, 3D (wax, mud); collect with clay/putty, cast, recreate on paper.
- Analysis: Compare via digital tools, magnifying glass, or microscope.
- Note: Fingerprints are stable but may smudge with age or temporary damage (burns, scars).
Fingerprint Tech
- Focus Question: How are fingerprints used?
- AFIS: Automated Fingerprint Identification System compares prints to millions in minutes.
- Video Insights (Due Process):
- IAFIS: FBI’s fingerprint/criminal history database, includes 70M+ suspect prints, 30M+ civil prints.
- Advantage: Rapid response (e.g., 15 minutes) prevents suspect release under alias.
- Fingerprint Value: Individual evidence, unchanging, comparable via databases.
- Limitation: AFIS matches to groups, requires additional evidence.
- Case Applications:
- Panama Burglaries: AFIS solved case in one month vs. three months with local database.
- Ted Bundy: Smudged prints initially inconclusive, confirmed involvement post-arrest.
- Key Terms: AFIS, Arch, Delta, Loop, Whorl.
04.05 Glass and Paint Evidence
Road Rage Incident
- Incident: Man shot in road rage, suspect claimed self-defense.
- Evidence: Bullet hole in car window, glass pieces near deceased, particles in wound.
- Essential Question: How can glass and paint be used as evidence?
Glass Evidence
- Focus Question: Which characteristics of glass are important to an investigation?
- Types:
- Soda-lime Glass: 70% silicon dioxide, 15% sodium oxide, 10% calcium oxide; used in windows, bottles; shatters into sharp pieces.
- Tempered Glass: Heated/cooled rapidly, used in car windows; breaks into smooth-edged pieces.
- Windshield Glass: Two glass layers with plastic center, used in car windshields; cracks but stays intact.
- Characteristics: Striations, chemical composition, fracture patterns.
- Fractures:
- Radial: Outward cracks, opposite side of impact.
- Concentric: Circular cracks, same side of impact.
- Backscatter: Glass particles blown toward impact direction.
- Analysis: Fractures indicate direction/force; velocity increases fracture count.
Glass Analysis
- Focus Question: How is glass analyzed and collected?
- Importance: Class evidence, links victim/suspect (e.g., glass shard match).
- Characteristics: Thickness, breaking pattern, color.
- Impact Source:
- Cone of Impact: Indicates force direction (facing observer = opposite side impact).
- Angle of Entry: Round hole (straight), oval hole (angled).
- Refractive Index:
- Submersion Test: Glass “disappears” in matching liquid.
- Becke Lines: Halo around glass under microscope if refractive index differs.
- Collection:
- Photograph scene, record characteristics.
- Store large pieces in boxes, small fragments in envelopes/pill bottles.
- Label fragments with distance from impact.
- Collect all glass in motor vehicle accidents.
Paint Evidence
- Focus Question: Which characteristics of paint are important to an investigation?
- Properties:
- Physical: Color, layer sequence, thickness, weathering.
- Chemical: Pigment, polymer, additive composition.
- Characteristics:
- Pattern: Voids indicate paint chip transfer.
- Layers: Match to repainted surfaces.
- Composition: Links to manufacturer, car make/model/year.
Paint Analysis
- Focus Question: How is paint analyzed and collected?
- Methods:
- Microscopic Examination: Compare paint layers via comparison microscope.
- Gas Chromatography: Heat/gas separates paint compounds.
- UV Spectrophotometry: Measures pigment absorption under UV light.
- Collection:
- Photograph scene, note colors/layers.
- Store large pieces in envelopes/pill bottles, small particles with tape.
- Key Terms: Backscatter, Becke line, Concentric fracture, Pigment, Radial fracture, Refraction, Refractive index, Submersion test, Soda-lime glass, Tempered glass.
04.06 Blood Spatter Evidence
Library Killer
- Case: Librarian murdered coworker, claimed crime of passion; evidence suggested premeditated beating.
- Contradictory Evidence: Blood on walls showed multiple impacts.
- Essential Question: How is blood spatter used in a forensic investigation?
Events That Cause Spatter
- Focus Question: What inferences can scientists make from blood spatter evidence?
- Definition: Blood spatter tracks blood path post-impact; class evidence, circumstantial.
- Types:
- Passive: Circular drops from gravity.
- Impact: Tiny drops from forceful impact.
- Transfer: Smeared blood from object movement.
- Inferences:
- Linear Pattern: Indicates trajectory, direction, weapon type, number of wounds.
- Example: Pillow spatter showed impact, knife/sharp weapon, upward/left trajectory, victim stationary, one wound.
- Collection:
- Photograph with ruler.
- Note blood location, voids, objects.
- Cut out surfaces with spatter, collect objects (clothes, furniture).
Patterns of Spatter
- Focus Question: What information do spatter patterns provide?
- Analysis Goal: Recreate crime scene events accurately.
- Types:
- High Impact: <1mm droplets, 100ft/sec, gunshot.
- Medium Impact: 1-4mm droplets, 25ft/sec, stabbing/blunt object.
- Low Impact (Passive): >4mm droplets, 5ft/sec, dripping wound.
- Directionality:
- Direct: 90-degree drops (vertical or horizontal entry).
- Angled: Tail indicates impact direction (e.g., left/upward).
- Importance: Accurate analysis prevents false accusations.
Source of Spatter
- Focus Question: How do forensic experts determine the source of blood spatter?
- Methods:
- Area of Convergence: Backtrack drop angles to intersect point (victim location).
- Area of Origin: Uses convergence, angle, trajectory to determine victim height (standing, sitting, lying).
- Inferences:
- Voids: Missing spatter indicates object presence.
- Source: Arterial (large drops), venous (smaller, irregular).
- Amount: Higher blood pressure (standing) = more blood; lower (lying) = less.
- Blood Stain Pattern Analyst:
- Role: Analyze, photograph, reconstruct crime scenes.
- Education: Bachelor’s in natural sciences (chemistry, biology).
- Certification: Varies by state, IABPA training.
- Skills: Communication, photography, problem-solving, computer skills.
Review the Case
- Killer Librarian:
- Blood Spatter: Multiple impacts, four feet up on wall, suggested standing attacker.
- Contradiction: Multiple impacts disproved single-blow “rage” claim.
- Key Terms: Angle, Impact blood spatter, Passive blood spatter, Trajectory, Transfer blood spatter.
04.07 Forensic Psychology
Politician Killer
- Case: Mayor and supervisor killed, suspect (board member) convicted of voluntary manslaughter, served five years.
- Reason: Psychological investigation (“Twinkie Defense” – stress, junk food, diminished capacity).
- Essential Question: How can psychology help solve a crime?
Criminal Profiling
- Focus Question: What information can a criminal profile provide?
- Definition: Identifies suspect’s mental, emotional, personality characteristics, and behavioral patterns.
- Types:
- Crime Scene Profiling: Deduce event sequence (e.g., crowbar marks, footprints suggest stalking).
- Geographical Profiling: Crime locations reveal suspect habits/residence.
- Suspect-Based Profiling: Analyzes emotional, cognitive, behavioral, demographic status, past offenses.
- Psychological Profiling: Examines tools/strategies (M.O.) to reveal personality/lifestyle (e.g., organized = intelligent, stable).
- Psychological Autopsy: Assesses deceased’s mental state via records, interviews.
- Case: Politician killer’s profile indicated crime of passion, reduced charges.
Profiling Methods
- Focus Question: What methods are used to build a criminal profile?
- Approaches:
- Top-Down: Starts with big picture, uses past crime data, common in U.S., categorizes suspects (organized/disorganized).
- Bottom-Up: Starts with details, evidence-based, no assumptions, common in U.K.
- Challenges: Inconsistent human behavior, limited psychological data, requires concrete evidence.
Review the Case
- Ted Bundy:
- Profile: Confusing upbringing (raised by grandparents, mother as sister), fascination with knives/peeping/stealing, lacked empathy, targeted women resembling ex-girlfriend (long, dark hair).
- M.O.: Pretended injury to gain trust, increased murders post-escape.
- Insights: Genetic predisposition, upbringing influenced victim selection.
- Key Terms: Bottom-up approach, Criminal profiling, Crime scene profiling, Geographical profiling, Forensic psychology, Psychological autopsy, Psychological profiling, Suspect-based profiling, Top-down approach.
04.08 Pattern Evidence Discussion-Based Assessment
- Topics for Review:
- Pattern Evidence
- Casts and Impressions
- Tool Marks
- Types of Fingerprints
- Glass Evidence
- Paint Evidence
- Blood Spatter Evidence
- Collection/Analysis of Pattern Evidence
- Criminology Profiling
- Preparation: Review guided notes, reflect on module survey answers.
Forensic Science: Pattern Evidence - Discussion-Based Assessment Review Notes
- Pattern Evidence
- Definition: Evidence resulting from physical contact between an object and a surface, creating impressions or marks.
- Types: Bite marks, footprints, tire tracks, tool marks, fingerprints, blood spatter.
- Characteristics: Often circumstantial, requiring supporting evidence for courtroom use; fingerprints are individual evidence, others are class evidence.
- Role in Investigations: Helps reconstruct crime scenes, link suspects to crimes, and provide demonstrative evidence in court.
- Example: In the Ted Bundy case, a bite mark was pivotal in linking him to murders across three states, supported by witness accounts, fingerprints, and blood evidence.
- Casts and Impressions
- Definition: Physical replicas (casts) or marks (impressions) of evidence like bite marks, footprints, or tire tracks.
- Types:
- Patent: Visible, 2D (e.g., footprint in blood).
- Latent: Invisible until processed, 2D (e.g., dusted fingerprint).
- Plastic: Visible, 3D (e.g., footprint in mud).
- Collection Methods:
- Photographing: Include ruler for scale, mark relative positions.
- Casting: Use plaster/putty for 3D impressions.
- Electrostatic Dust Lifter: Attracts dust from latent prints for imaging.
- Importance: Recreates crime scene marks for comparison to suspect items (e.g., shoes, tires, teeth).
- Ted Bundy Case: Bite mark cast matched his crooked incisor, strengthening case with other evidence.
- Note: Impressions are critical for demonstrative evidence, but their uniqueness varies (e.g., bite marks more unique with irregular teeth).
- Tool Marks
- Definition: Impressions or material transfers from tools (e.g., knives, pry bars) contacting surfaces.
- Common Tools and Marks:
- Pry Bars: Two-prong marks, possible paint transfer.
- Screwdrivers: End bit marks, vary by wear.
- Hammers: Circular marks.
- Knives: Slice/stab marks, possible blade fragments.
- Bullets: Striations from gun barrels.
- Collection: Photograph with ruler, collect object or cast mark, confirm crime relevance.
- Analysis: Microscopic comparison to sample tools, use of NRBTD (tool marks) and NIBIN (ballistic) databases.
- MacDonald Case: Bloody splinters matched a wooden club, knife placement was suspicious, ice pick matched wife’s wounds.
- Note: Tool marks can be class (group of tools) or individual (specific tool) evidence.
- Types of Fingerprints
- Patterns:
- Arch: 5% of fingerprints, ridges flow in/out opposite sides, 0 deltas.
- Loop: 60%, ridges flow in/out same side, 1 delta.
- Whorl: 35%, circular ridges, 2 deltas.
- Uniqueness: Determined by chaotic ridge growth (influenced by nerves, capillaries, fluid pressure, gravity), not just DNA.
- Types:
- Patent: Visible, 2D (e.g., blood, ink); collected via tape/photograph.
- Latent: Invisible until processed (powders, UV, fumes); collected via dusting or electrostatic lifter.
- Plastic: Visible, 3D (e.g., in wax); collected via clay/putty casts.
- Analysis: Compared via digital tools (AFIS), magnifying glass, or microscope.
- Case Examples:
- Panama Burglaries: AFIS matched digital fingerprint, solved case in one month.
- Ted Bundy: Smudged prints initially inconclusive, confirmed post-arrest.
- Note: Fingerprints are individual evidence, unchanging from womb, critical for identification.
- Glass Evidence
- Types:
- Soda-lime Glass: Windows, bottles; shatters into sharp pieces.
- Tempered Glass: Car side/rear windows; breaks into smooth-edged pieces.
- Windshield Glass: Two layers with plastic center; cracks but stays intact.
- Characteristics: Chemical composition, striations, fracture patterns (radial: opposite impact side; concentric: same side).
- Analysis:
- Impact Source: Cone of force indicates direction.
- Angle of Entry: Round (straight) or oval (angled) holes.
- Refractive Index: Submersion test (glass disappears in matching liquid), Becke lines (halo under microscope).
- Collection: Photograph, store large pieces in boxes, small fragments in envelopes/pill bottles, label distance from impact.
- Road Rage Case: Bullet hole, glass pieces, and wound particles confirmed shooter’s story.
- Note: Glass is class evidence but links suspects/victims (e.g., matching shards).
- Paint Evidence
- Properties:
- Physical: Color, layer sequence, thickness, weathering.
- Chemical: Pigment, polymer, additive composition.
- Characteristics:
- Pattern: Voids indicate chip transfer.
- Layers: Match to repainted surfaces.
- Composition: Links to manufacturer, car make/model/year.
- Analysis:
- Microscopic Examination: Compare layers via comparison microscope.
- Gas Chromatography: Separates compounds.
- UV Spectrophotometry: Analyzes pigment absorption.
- Collection: Photograph, note colors/layers, store in envelopes/pill bottles or with tape.
- Note: Paint transfers between objects, critical for linking suspects to crime scenes.
- Blood Spatter Evidence
- Definition: Tracks blood path post-impact, indicates injury mode/force.
- Types:
- Passive: Circular drops from gravity (>4mm, 5ft/sec).
- Impact: Tiny drops from force (<1mm high impact, 100ft/sec; 1-4mm medium impact, 25ft/sec).
- Transfer: Smeared blood from object movement.
- Analysis:
- Area of Convergence: Backtrack drop angles to victim location.
- Area of Origin: Determines victim height (standing, sitting, lying).
- Inferences: Trajectory, weapon type, number of wounds, victim movement.
- Collection: Photograph with ruler, note voids/objects, cut out surfaces, collect items with spatter.
- Library Killer Case: Multiple impacts on wall (four feet up) disproved single-blow “rage” claim.
- Blood Stain Pattern Analyst: Requires science degree, IABPA certification, skills in photography, reconstruction.
- Note: Class evidence, requires careful analysis to avoid misinterpretation.
- Collection of Pattern Evidence
- General Steps:
- Photograph with ruler for scale.
- Record observations (location, physical characteristics).
- Collect objects or make casts (e.g., plaster for 3D impressions, tape for small particles).
- Use specialized tools (e.g., electrostatic dust lifter for latent prints).
- Specifics:
- Bite Marks: Swab for DNA, photograph, outline tooth marks.
- Fingerprints: Tape (patent), dusting (latent), clay casts (plastic).
- Glass/Paint: Boxes for large pieces, envelopes/pill bottles for fragments.
- Blood Spatter: Cut out surfaces, collect items with spatter.
- Importance: Preserves evidence integrity for courtroom use.
- Analysis of Pattern Evidence
- Methods:
- Microscopic Comparison: Tool marks, paint layers, glass fractures.
- Digital Tools: AFIS for fingerprints, NIBIN/NRBTD for ballistic/tool marks.
- Chemical Analysis: Gas chromatography, UV spectrophotometry for paint.
- Trajectory Analysis: Blood spatter angles for convergence/origin.
- Databases: Enhance matching (e.g., AFIS for fingerprints, NIBIN for ballistics).
- Challenges: Class evidence (e.g., tire tracks, paint) requires supporting evidence; individual evidence (fingerprints) more conclusive.
- Note: Analysis must be precise to avoid false positives/negatives.
- Criminology Profiling
- Definition: Identifies suspect’s mental, emotional, personality, and behavioral characteristics.
- Types:
- Crime Scene Profiling: Deduce event sequence (e.g., stalking behavior).
- Geographical Profiling: Crime locations indicate suspect habits/residence.
- Suspect-Based Profiling: Analyzes emotional/cognitive status, past offenses.
- Psychological Profiling: Examines M.O. (e.g., organized vs. disorganized).
- Psychological Autopsy: Assesses deceased’s mental state.
- Approaches:
- Top-Down: Big picture, past crime data, U.S.-common.
- Bottom-Up: Detail-driven, evidence-based, U.K.-common.
- Ted Bundy Case: Profile showed M.O. (targeting women resembling ex-girlfriend), influenced by upbringing and genetics.
- Politician Killer Case: “Twinkie Defense” reduced charge due to stress-induced diminished capacity.
- Note: Requires concrete evidence, as human behavior is inconsistent.
Additional Notes
- Preparation: Review guided notes, reflect on module survey responses for discussion.
- Key Considerations: Pattern evidence often requires corroboration; individual evidence (fingerprints, unique bite marks) is more conclusive.
- Sensitivity Warning: Case studies (e.g., Bundy, MacDonald) may involve sensitive content; consult parent/guardian if needed.
Forensic Science: Pattern Evidence - Enhanced Discussion-Based Assessment Review Notes
Below are detailed notes for the Discussion-Based Assessment, organized by topic with concise summaries, key takeaways, and mnemonic aids to aid retention when listening via text-to-speech. These notes are designed for easy copying into Google Docs and cover all required topics from the Forensic Science: Pattern Evidence module.
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- Pattern Evidence
- Definition: Evidence from physical contact between an object and a surface, creating impressions or marks.
- Types: Bite marks, footprints, tire tracks, tool marks, fingerprints, blood spatter.
- Characteristics: Mostly circumstantial (class evidence), requiring supporting evidence; fingerprints are individual evidence.
- Role in Investigations: Reconstructs crime scenes, links suspects to crimes, provides demonstrative evidence in court.
- Example: Ted Bundy’s bite mark linked him to murders across Washington, Utah, and Colorado; supported by witness accounts, fingerprints, and blood evidence.
- Summary: Pattern evidence includes various impressions used to piece together crime scenes, with fingerprints being uniquely individual.
- Key Takeaway: Most pattern evidence is circumstantial and needs corroboration, except fingerprints, which are definitive.
- Mnemonic: "BFTTFB" – Bite marks, Footprints, Tire tracks, Tool marks, Fingerprints, Blood spatter.
- Casts and Impressions
- Definition: Physical replicas (casts) or marks (impressions) of evidence like bite marks, footprints, or tire tracks.
- Types:
- Patent: Visible, 2D (e.g., footprint in blood).
- Latent: Invisible until processed, 2D (e.g., dusted fingerprint).
- Plastic: Visible, 3D (e.g., footprint in mud).
- Collection Methods:
- Photographing: Include ruler for scale, mark relative positions.
- Casting: Use plaster/putty for 3D impressions.
- Electrostatic Dust Lifter: Attracts dust from latent prints for imaging.
- Importance: Recreates crime scene marks for comparison to suspect items (e.g., shoes, tires, teeth).
- Ted Bundy Case: Bite mark cast matched his crooked incisor, strengthening the case with other evidence.
- Note: Impressions vary in uniqueness; irregular teeth marks are more confirmatory than common patterns.
- Summary: Casts and impressions preserve crime scene marks for analysis, bridging physical evidence to suspects.
- Key Takeaway: Proper collection (photography, casting) ensures accurate courtroom recreation.
- Mnemonic: "PLC" – Patent, Latent, Cast (for impression types).
- Tool Marks
- Definition: Impressions or material transfers from tools (e.g., knives, pry bars) contacting surfaces.
- Common Tools and Marks:
- Pry Bars: Two-prong marks, possible paint transfer.
- Screwdrivers: End bit marks, vary by wear.
- Hammers: Circular marks.
- Knives: Slice/stab marks, possible blade fragments.
- Bullets: Striations from gun barrels.
- Collection: Photograph with ruler, collect object or cast mark, confirm crime relevance.
- Analysis: Microscopic comparison, NRBTD (tool marks) and NIBIN (ballistic) databases.
- MacDonald Case: Bloody splinters matched a wooden club, knife placement suspicious, ice pick matched wife’s wounds.
- Summary: Tool marks link specific tools to crimes, with databases aiding identification.
- Key Takeaway: Marks can be class or individual, requiring careful analysis to pinpoint tools.
- Mnemonic: "PSTHBKR" – Pry bars, Screwdrivers, Tools (general), Hammers, Bullets, Knives, Razorblades.
- Types of Fingerprints
- Patterns:
- Arch: 5%, ridges flow in/out opposite sides, 0 deltas.
- Loop: 60%, ridges flow in/out same side, 1 delta.
- Whorl: 35%, circular ridges, 2 deltas.
- Uniqueness: Chaotic ridge growth (nerves, capillaries, fluid pressure, gravity), not just DNA.
- Types:
- Patent: Visible, 2D (e.g., blood, ink); tape/photograph collection.
- Latent: Invisible until processed (powders, UV, fumes); dusting or electrostatic lifter.
- Plastic: Visible, 3D (e.g., in wax); clay/putty casts.
- Analysis: Digital (AFIS), magnifying glass, or microscope comparison.
- Case Examples:
- Panama Burglaries: AFIS matched digital fingerprint, solved in one month.
- Ted Bundy: Smudged prints confirmed involvement post-arrest.
- Note: Fingerprints are individual, unchanging from womb, critical for identification.
- Summary: Fingerprints are unique, with three patterns and collection methods tailored to type.
- Key Takeaway: AFIS speeds up identification, but matches often need corroboration.
- Mnemonic: "ALW" – Arch (0 deltas), Loop (1 delta), Whorl (2 deltas).
- Glass Evidence
- Types:
- Soda-lime Glass: Windows, bottles; sharp-edged shards.
- Tempered Glass: Car side/rear windows; smooth-edged pieces.
- Windshield Glass: Two layers with plastic center; cracks but stays intact.
- Characteristics: Chemical composition, striations, fractures (radial: opposite impact side; concentric: same side).
- Analysis:
- Impact Source: Cone of force shows direction.
- Angle of Entry: Round (straight) or oval (angled) holes.
- Refractive Index: Submersion test, Becke lines.
- Collection: Photograph, store large pieces in boxes, small fragments in envelopes/pill bottles, label distance from impact.
- Road Rage Case: Bullet hole, glass pieces, and wound particles confirmed shooter’s story.
- Summary: Glass evidence reveals impact details and links suspects/victims via matching shards.
- Key Takeaway: Fractures and refractive index pinpoint impact direction and glass type.
- Mnemonic: "STR" – Soda-lime, Tempered, Reinforced (windshield).
- Paint Evidence
- Properties:
- Physical: Color, layer sequence, thickness, weathering.
- Chemical: Pigment, polymer, additive composition.
- Characteristics:
- Pattern: Voids indicate chip transfer.
- Layers: Match to repainted surfaces.
- Composition: Links to manufacturer, car make/model/year.
- Analysis:
- Microscopic Examination: Compare layers.
- Gas Chromatography: Separate compounds.
- UV Spectrophotometry: Analyze pigment absorption.
- Collection: Photograph, note colors/layers, store in envelopes/pill bottles or with tape.
- Summary: Paint transfers link suspects to crime scenes, with layers and composition aiding identification.
- Key Takeaway: Small paint samples can identify specific vehicles or objects.
- Mnemonic: "PLC" – Pattern, Layers, Composition.
- Blood Spatter Evidence
- Definition: Tracks blood path post-impact, indicating injury mode/force.
- Types:
- Passive: Circular drops (>4mm, 5ft/sec, gravity).
- Impact: Tiny drops (<1mm high, 100ft/sec, gunshot; 1-4mm medium, 25ft/sec, stabbing).
- Transfer: Smeared blood from object movement.
- Analysis:
- Area of Convergence: Backtrack angles to victim location.
- Area of Origin: Determines victim height (standing, sitting, lying).
- Inferences: Trajectory, weapon, wounds, victim movement.
- Collection: Photograph with ruler, note voids/objects, cut out surfaces, collect items.
- Library Killer Case: Multiple impacts on wall disproved single-blow “rage” claim.
- Analyst Role: Science degree, IABPA certification, skills in photography/reconstruction.
- Summary: Blood spatter reconstructs crime events, indicating weapon and victim position.
- Key Takeaway: Accurate analysis is critical to avoid misinterpretation.
- Mnemonic: "PIT" – Passive, Impact, Transfer.
- Collection of Pattern Evidence
- General Steps:
- Photograph with ruler for scale.
- Record observations (location, characteristics).
- Collect objects or make casts (plaster for 3D, tape for small particles).
- Use specialized tools (e.g., electrostatic dust lifter).
- Specifics:
- Bite Marks: Swab DNA, photograph, outline teeth.
- Fingerprints: Tape (patent), dusting (latent), clay casts (plastic).
- Glass/Paint: Boxes for large pieces, envelopes/pill bottles for fragments.
- Blood Spatter: Cut surfaces, collect items with spatter.
- Importance: Preserves evidence integrity for courtroom use.
- Summary: Systematic collection ensures evidence is preserved accurately.
- Key Takeaway: Ruler inclusion and proper storage are critical for all pattern evidence.
- Mnemonic: "PRC" – Photograph, Record, Collect.
- Analysis of Pattern Evidence
- Methods:
- Microscopic Comparison: Tool marks, paint layers, glass fractures.
- Digital Tools: AFIS (fingerprints), NIBIN/NRBTD (ballistic/tool marks).
- Chemical Analysis: Gas chromatography, UV spectrophotometry (paint).
- Trajectory Analysis: Blood spatter angles.
- Databases: Enhance matching efficiency.
- Challenges: Class evidence needs corroboration; individual evidence (fingerprints) more conclusive.
- Summary: Analysis combines physical, chemical, and digital methods to match evidence.
- Key Takeaway: Precision prevents false positives/negatives.
- Mnemonic: "MCD" – Microscopic, Chemical, Digital.
- Criminology Profiling
- Definition: Identifies suspect’s mental, emotional, personality, and behavioral characteristics.
- Types:
- Crime Scene Profiling: Event sequence (e.g., stalking).
- Geographical Profiling: Crime locations reveal habits/residence.
- Suspect-Based Profiling: Emotional/cognitive status, past offenses.
- Psychological Profiling: M.O. reveals personality (e.g., organized).
- Psychological Autopsy: Deceased’s mental state.
- Approaches:
- Top-Down: Big picture, past crime data, U.S.-common.
- Bottom-Up: Detail-driven, evidence-based, U.K.-common.
- Cases:
- Ted Bundy: M.O. (targeting women like ex-girlfriend), influenced by upbringing/genetics.
- Politician Killer: “Twinkie Defense” reduced charge due to stress.
- Summary: Profiling uses behavioral clues to narrow suspect profiles, requiring concrete evidence.
- Key Takeaway: Profiling is complex and needs corroboration due to inconsistent human behavior.
- Mnemonic: "CGSP" – Crime scene, Geographical, Suspect-based, Psychological.
Additional Enhancements for Listening/Studying
- Listening Tips: When using text-to-speech, pause after each section to process. Repeat mnemonics aloud to reinforce memory (e.g., “BFTTFB” for pattern evidence types).
- Study Strategy: Highlight key terms in Google Docs (e.g., AFIS, NIBIN) for quick reference. Create flashcards for mnemonics and key takeaways.
- Sensitivity Note: Cases like Bundy and MacDonald involve sensitive content; review with care.