Criminalistics
"Future Forensic Expert! Criminalistics ang science sa likod ng crime solving - DNA analysis, fingerprinting, ballistics, at marami pa! Ito ang mga tools na nagpapatunay ng ebidensya sa court!"
1. Introduction to Criminalistics 🔬
Criminalistics (Forensic Science) is the application of natural sciences to matters of law. It's the scientific examination of physical evidence.
📊 Branches of Criminalistics:
- • Dactyloscopy - Fingerprint examination
- • Ballistics - Firearms identification
- • Questioned Documents - Document analysis
- • Forensic Chemistry - Drug analysis
- • DNA Analysis - Genetic identification
- • Forensic Photography - Crime scene photos
- • Polygraphy - Lie detection
- • Forensic Medicine - Medico-legal examination
💡 Locard's Exchange Principle
"Every contact leaves a trace." When two objects come into contact, there is always transfer of material. This is the foundation of forensic science!
2. Fingerprinting (Dactyloscopy) 🖐️
No two fingerprints are exactly alike - kahit identical twins! Fingerprints are the most common and reliable means of personal identification.
📊 Three Basic Fingerprint Patterns:
| Pattern | Frequency | Characteristics |
|---|---|---|
| LOOP | 60-65% | Ridges enter/exit same side; has delta and core (Ulnar Loop, Radial Loop) |
| WHORL | 30-35% | Circular/spiral pattern; has TWO deltas (Plain, Central Pocket, Double Loop, Accidental) |
| ARCH | 5% | Ridges enter one side, rise, exit other side; NO delta (Plain Arch, Tented Arch) |
📍 Key Fingerprint Terms
- • Delta: Triangular ridge pattern
- • Core: Center/innermost point
- • Ridge: Raised friction skin
- • Minutiae: Ridge characteristics (endings, bifurcations, dots)
🔬 Types of Fingerprint Evidence
- • Visible/Patent: Made with blood, paint, ink
- • Plastic/Molded: Impression on soft surface
- • Latent: Invisible; needs development (most common)
🧪 Developing Latent Fingerprints
Powder Dusting
Black/white powder for smooth surfaces
Ninhydrin
For porous surfaces (paper)
Cyanoacrylate (Super Glue)
Fuming method for non-porous
Silver Nitrate
Reacts with salt in sweat
Iodine Fuming
Temporary brown staining
AFIS
Automated database matching
3. Forensic Ballistics 🔫
The science of firearms and ammunition examination. Used to link bullets/casings to specific weapons.
📊 Three Branches of Ballistics:
| Branch | Focus | Examines |
|---|---|---|
| Interior Ballistics | Inside the gun | Ignition, pressure, projectile movement in barrel |
| Exterior Ballistics | In flight | Trajectory, velocity, range, drop, wind effects |
| Terminal Ballistics | Impact on target | Wound characteristics, penetration, stopping power |
🔍 Individual Characteristics
Unique marks that identify specific firearm:
- • Rifling marks on bullet (lands & grooves)
- • Firing pin impression on primer
- • Breech face marks on cartridge case
- • Extractor/Ejector marks
📋 Class Characteristics
Shared by group of firearms:
- • Caliber (diameter of bore)
- • Number of lands and grooves
- • Direction of twist (right/left)
- • Width of lands and grooves
💡 Gunshot Residue (GSR) Analysis
Particles discharged when firearm is fired. Contains: Lead, Barium, Antimony. Can be detected on hands of shooter up to 6-8 hours after firing using SEM-EDX analysis.
4. Questioned Documents Examination ✍️
Scientific examination of documents to detect forgery, alterations, or to determine authorship.
📊 Types of Document Examination:
Handwriting Analysis
- • Slant and slope
- • Pressure patterns
- • Letter spacing
- • Pen lifts
- • Line quality
- • Connecting strokes
Document Alterations
- • Erasures (physical/chemical)
- • Obliterations
- • Insertions
- • Substitutions
- • Overwriting
- • Ink analysis
📝 Forgery Types
- • Simple/Simulated: Freehand imitation
- • Traced: Carbon, light table
- • Photocopied: Cut and paste
🔬 Examination Tools
- • Microscope
- • UV/IR light
- • ESDA (indented writing)
- • Video Spectral Comparator
📋 Standard Specimens
- • Requested: Written for examination
- • Collected: Normal writings from subject
- • Minimum 10-20 specimens needed
5. DNA Analysis 🧬
The "gold standard" of forensic identification. DNA is unique to each individual (except identical twins).
📊 Sources of DNA Evidence:
Blood
Most common source
Semen
Sexual assault cases
Saliva
Cigarettes, cups
Hair
Must have root
Skin Cells
Touch DNA
Bone
Skeletal remains
Teeth
Disaster victims
Urine
Contains epithelial cells
🔬 DNA Testing Methods
- • PCR (Polymerase Chain Reaction): Amplifies DNA
- • STR Analysis: Short Tandem Repeats (current standard)
- • RFLP: Older method, needs more DNA
- • Mitochondrial DNA: Maternal lineage
📋 CODIS Database
Combined DNA Index System - FBI's national DNA database. Contains profiles from:
- • Convicted offenders
- • Arrestees
- • Forensic samples (crime scenes)
- • Missing persons
6. Forensic Medicine (Medico-Legal) 🏥
Application of medical knowledge to legal questions - especially in death investigations.
💀 Post-Mortem Changes (Signs of Death):
| Sign | Description | Time of Onset |
|---|---|---|
| Algor Mortis | Cooling of body (drops ~1.5°F/hr) | Immediate |
| Livor Mortis | Pooling of blood (purple discoloration) | 30 min - 2 hrs; fixed at 8-12 hrs |
| Rigor Mortis | Muscle stiffening | 2-6 hrs; complete at 12 hrs; gone at 24-36 hrs |
| Decomposition | Bacterial breakdown | Depends on environment |
🔪 Manner of Death
- • Natural: Disease, illness
- • Homicide: Killed by another
- • Suicide: Self-inflicted
- • Accident: Unintentional
- • Undetermined: Cannot determine
🩺 Types of Wounds
- • Incised: Longer than deep (knife)
- • Stab: Deeper than long
- • Laceration: Torn/jagged edges
- • Contusion: Bruise
- • Gunshot: Entry/exit wounds
7. Polygraphy (Lie Detection) 📈
Scientific method of detecting deception through physiological responses.
📊 Components Measured by Polygraph:
Pneumograph
Respiration
Breathing rate/depth
Cardiosphygmograph
Blood Pressure
Heart rate
Galvanograph (GSR)
Skin Conductance
Sweat gland activity
⚠️ Legal Status: Polygraph results are generally NOT admissible as evidence in Philippine courts but may be used for investigative leads. Subject must give INFORMED CONSENT.
📝 Practice Questions
1. What are the three basic fingerprint patterns and their approximate frequencies?
Show Answer
Loop (60-65%), Whorl (30-35%), and Arch (5%). Loops are most common and have one delta; Whorls have two deltas; Arches have no delta.
2. What is Locard's Exchange Principle?
Show Answer
"Every contact leaves a trace." When two objects come into contact, there is always a transfer of material between them. This is the fundamental principle of forensic science.
3. Rigor mortis is complete at approximately how many hours after death?
Show Answer
12 hours. Rigor mortis begins 2-6 hours after death, becomes complete/maximum at 12 hours, and disappears at 24-36 hours.
4. What three physiological responses does a polygraph measure?
Show Answer
(1) Respiration via Pneumograph, (2) Blood pressure/pulse via Cardiosphygmograph, (3) Skin conductance/sweat via Galvanograph (GSR).
🎯 Exam Strategy Tips
📚 High-Yield Topics:
- ✓ Fingerprint patterns (Loop, Whorl, Arch)
- ✓ Post-mortem changes (Algor, Livor, Rigor)
- ✓ Ballistics branches and markings
- ✓ DNA sources and analysis methods
- ✓ Polygraph components
💡 Memory Tips:
- ✓ "LAW" = Loop (most common), Arch (rarest), Whorl
- ✓ "ALR Dead" = Algor, Livor, Rigor, Decomposition
- ✓ "IET" = Interior, Exterior, Terminal ballistics
- ✓ "PCG" = Pneumograph, Cardiosphygmograph, Galvanograph
Test Your Knowledge! 🧠
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