Criminalistics
Forensic Sciences, Fingerprints, Ballistics & Evidence
Branches of Criminalistics
Forensic Chemistry
- Drug identification and analysis
- Toxicology (poison detection)
- DNA analysis
- Blood and body fluid analysis
- Arson investigation
Questioned Documents
- Handwriting analysis
- Forgery detection
- Ink and paper analysis
- Alterations and erasures
- Typewriting identification
Forensic Ballistics
- Firearm identification
- Bullet and cartridge comparison
- Gunshot residue analysis
- Trajectory determination
- Muzzle-to-target distance
Dactyloscopy
- Fingerprint classification
- Latent print development
- AFIS (Automated Fingerprint ID)
- Palm and footprint analysis
- Comparison and identification
Forensic Photography
- Crime scene documentation
- Evidence photography
- Surveillance photography
- Mug shot photography
Polygraphy
- Lie detection examination
- Physiological responses
- Pre-employment screening
- Criminal investigation aid
Dactyloscopy (Fingerprint Science)
Three Fundamental Principles
- Permanence - Fingerprints remain unchanged from birth to death
- Individuality - No two fingerprints are exactly alike
- Infallibility - Fingerprints are a reliable means of identification
Fingerprint Patterns
Loop (60-65%)
Most common pattern. Ridges enter from one side, curve, and exit from the same side.
Ulnar Loop: Opens toward little finger
Radial Loop: Opens toward thumb
Whorl (30-35%)
Circular or spiral pattern. Has at least two deltas.
Plain Whorl, Central Pocket Loop
Double Loop, Accidental Whorl
Arch (5%)
Ridges enter from one side, rise in center, exit opposite side. No delta.
Plain Arch: Smooth wave
Tented Arch: Sharp peak
Types of Fingerprints
Latent Prints
Invisible prints left by sweat/oils; require development
Patent Prints
Visible prints left in blood, ink, paint, etc.
Plastic Prints
3D impressions in soft materials (wax, clay, soap)
Latent Print Development Methods
Physical Methods:
- Fingerprint powder dusting
- Magna brush (magnetic powder)
- Iodine fuming
- Laser/alternate light source
Chemical Methods:
- Ninhydrin (paper/cardboard)
- Silver nitrate
- Cyanoacrylate fuming (Super Glue)
- DFO (1,8-Diazafluoren-9-one)
Forensic Ballistics
Types of Ballistics
Interior Ballistics
Study of projectile inside the firearm
Exterior Ballistics
Study of projectile in flight
Terminal Ballistics
Study of projectile at impact
Identification Marks on Bullets
- Land Impressions: Raised marks from rifling grooves
- Groove Impressions: Recessed marks from lands of barrel
- Striation Marks: Individual microscopic scratches
Identification Marks on Cartridge Cases
- Firing Pin Impression: Mark from firing pin strike
- Breech Face Marks: Marks from breech bolt
- Extractor Marks: Marks from extraction
- Ejector Marks: Marks from ejection
Gunshot Residue (GSR) Tests
- Paraffin Test (Diphenylamine): Detects nitrates on hands
- Neutron Activation Analysis: More accurate, detects antimony/barium
- Atomic Absorption: Detects lead, barium, antimony
Note: Paraffin test is not conclusive as nitrates can come from other sources.
Questioned Documents Examination
Definition
A questioned document is any document whose origin, authorship, or authenticity is in doubt.
Types of Documents Examined
- Checks and financial documents
- Wills and contracts
- Letters and notes
- Identification documents
- Medical/legal records
Examination Methods
- Handwriting comparison
- Ink analysis
- Paper analysis
- Indented writing examination
- Alterations/erasures detection
Handwriting Characteristics
Class Characteristics:
Shared by many writers (style taught in school)
Individual Characteristics:
Unique to a specific person (developed habits)
Types of Forgery
- Traced Forgery: Tracing over genuine signature
- Simulated Forgery: Freehand imitation of signature
- Blind Forgery: Signing without seeing original
Chain of Custody
Definition
The chronological documentation of the seizure, custody, control, transfer, analysis, and disposition of physical evidence. It ensures evidence integrity from collection to court presentation.
Key Principles
- Document WHO handled the evidence and WHEN
- Evidence must be properly marked and sealed
- Maintain integrity throughout the process
- Any gap in custody can compromise evidence admissibility
- Each transfer must be documented and signed
Chain of Custody Steps
- Collection - Proper collection and marking at crime scene
- Preservation - Proper packaging and storage
- Transfer - Documented hand-over between handlers
- Analysis - Laboratory examination and documentation
- Storage - Secure storage until court presentation
- Presentation - Evidence presented in court
- Disposition - Return, destruction, or retention after case
DNA Analysis
Sources of DNA Evidence
- Blood and blood stains
- Semen and vaginal fluid
- Saliva (on stamps, cups, cigarette butts)
- Hair with root
- Skin cells (touch DNA)
- Bone and teeth
DNA Profiling Methods
- PCR: Polymerase Chain Reaction (DNA amplification)
- STR: Short Tandem Repeat analysis
- mtDNA: Mitochondrial DNA (maternal lineage)
- Y-STR: Male lineage identification
R.A. 10054 (DNA Evidence Act)
Provides for the use of DNA evidence in Philippine courts. DNA evidence is admissible if it meets reliability standards and proper chain of custody is established.