Definition
Physical evidence refers to any tangible object or material that is relevant to a crime or legal investigation. It can be seen, touched, or measured and is used to establish facts, support or refute claims, and reconstruct events surrounding an incident. Physical evidence is often collected from crime scenes, victims, suspects, or objects involved in a case.
Properties
- Size
- Shape
- Weight (Mass)
- Color
- Texture
- Density
- Surface pattern or markings (e.g. striations, imprints)
- Hardness
- Flexibility
- Brittleness
- Temperature (at time of collection)
- Volume
- Odor (in some cases)
- Opacity or transparency
- Magnetic properties
- Conductivity (thermal or electrical)
- Residue or contamination presence
- Material composition (e.g., metal, glass, plastic)
- Moisture content
- Condition (e.g., broken, burned, intact)
Importance
- Provides objective and dependable proof
- Confirms or challenges witness accounts
- Clarifies key facts of the case
- Connects suspects with victims or crime locations
- Verifies or disproves statements made by witnesses
- Helps piece together the sequence of events
- Assists in identifying unknown individuals involved
- Clears innocent people from suspicion
- Offers new directions for investigation
- Strengthens the legal argument in court
Classification of Physical Evidence
Direct Evidence
Evidence that directly proves a fact (e.g., eyewitness testimony, video footage).
Circumstantial Evidence
Evidence that implies a fact but doesn’t directly prove it (e.g., fingerprints, DNA).
Transient Evidence
Temporary evidence that can change or disappear quickly (e.g., odors, temperature).
Pattern Evidence
Evidence that shows patterns or impressions (e.g., blood spatter, tire marks).
Conditional Evidence
Evidence based on specific conditions or actions (e.g., door open or closed, light on or off).
Associative Evidence
Evidence that links a suspect or victim to a location or object (e.g., personal belongings, fibers).
Physical Evidence by Type
- Biological: Blood, hair, saliva, tissues
- Chemical: Drugs, toxins, residues
- Impression: Fingerprints, footprints, tool marks
- Miscellaneous: Weapons, documents, digital evidence
- Digital Evidence: Data stored or transmitted electronically (e.g., emails, files, metadata).
Class Evidence:
Shares common characteristics with a group (e.g., type of shoe tread).
Individual Evidence:
Has unique features that can identify a single source (e.g., fingerprint, DNA).
Trace Evidence:
Small but measurable amounts of materials transferred during a crime (e.g., fibers, paint chips)
Types of physical evidences
1. Biological Evidence
Definition: Organic materials originating from a living organism that can provide DNA or other biological information.
- Blood
- Hair
- Saliva
- Semen
- Tissues
- Body fluids
2. Chemical Evidence
Definition: Substances that involve chemical compounds or reactions, often analyzed to identify drugs, toxins, or residues.
- Drugs (illegal or prescription)
- Poisons
- Toxins
- Residues (gunshot residue, explosive residue)
- Explosives
3. Physical/Impression Evidence
Definition: Objects or marks that record a physical impression or pattern caused by contact or force.
- Fingerprints
- Footprints
- Tire marks
- Tool marks (scratches, indentations)
- Bite marks
4. Trace Evidence
Definition: Small or microscopic materials transferred from one person or object to another during a crime.
- Fibers (from clothing, carpets)
- Paint chips
- Glass fragments
- Soil
- Pollen
5. Digital Evidence
Definition: Information stored or transmitted in digital form that can be used in an investigation.
- Emails
- Computer files
- Metadata (data about data)
- Electronic devices (computers, phones, USB drives)
6. Miscellaneous Evidence
Definition: Various physical items that don’t fit neatly into other categories but are relevant to an investigation.
- Weapons (guns, knives)
- Documents (forged papers, letters)
- Clothing
- Hardware (white hardware like screws, nails, hinges)
- Personal belongings (jewelry, wallets)
Identification of Physical Evidence
➤ Biological Evidence
- Identified by presence of blood, hair, saliva, semen, etc.
- May appear as stains, fluids, or tissue at the scene.
- Often detected visually, or using presumptive tests (e.g., luminol for blood)
➤ Chemical Evidence
- Identified through color, packaging, or residue
- Field test kits used for drugs or explosives
- May require lab confirmation (e.g., GC-MS for drugs)
➤ Physical/Impression Evidence
- Identified by visible patterns or markings (e.g., fingerprints, tool marks)
- Often found on surfaces, doors, windows, or bodies
➤ Trace Evidence
- Tiny particles like fibers, glass, paint
- Located using visual inspection, alternate light sources, or taping
➤ Digital Evidence
- Identified by presence of electronic devices (e.g., phones, laptops)
- Requires immediate power-down or proper handling
➤ Miscellaneous Evidence
- Items like weapons, documents, clothing
- Identified by relevance to the scene or suspect
Collection of Physical Evidence
➤ Biological Evidence
- Collected using sterile swabs, forceps, gloves
- Dried before packaging to prevent degradation
➤ Chemical Evidence
- Collected using sealable containers (e.g., jars, vials)
- Care taken to avoid contamination or reaction
➤ Physical/Impression Evidence
- Fingerprints lifted using tape or gel; impressions cast using dental stone
- Tools or weapons collected intact with gloves
➤ Trace Evidence
- Collected with tweezers, tape, or vacuum filters
- Packaged separately to avoid cross-contamination
➤ Digital Evidence
- Devices seized without alteration
- Screened for active data if allowed; otherwise, powered off and labeled
➤ Miscellaneous Evidence
- Handled based on type (e.g., firearms unloaded before packing)
- Documents placed in protective covers
Preservation of Physical Evidence
➤ Biological Evidence
- Stored in cool, dry conditions
- Paper bags used (not plastic) to prevent mold
➤ Chemical Evidence
- Stored according to chemical safety standards
- Flammable materials kept in fire-safe cabinets
➤ Physical/Impression Evidence
- Protected from smearing or distortion
- Casts allowed to fully set before packing
➤ Trace Evidence
- Prevented from being lost by sealing containers tightly
- Stored in stable, labeled containers
➤ Digital Evidence
- Shielded from electromagnetic interference
- Stored in Faraday bags if needed
➤ Miscellaneous Evidence
- Preserved according to material, rust prevention for metals, etc
- Proper labeling to maintain context
Packing & Forwarding of Physical Evidence
➤ Biological Evidence
- Packed in breathable paper bags/envelopes
- Labeled with case details and sealed with evidence tape
➤ Chemical Evidence
- Leak-proof containers, labeled with hazard warnings
- Shipped according to hazardous materials regulations
➤ Physical/Impression Evidence
- Fingerprint lifts placed on cards; impressions in boxes
- Secured to avoid movement
➤ Trace Evidence
- Individual packaging to prevent mixing
- Labeled clearly with collection site
➤ Digital Evidence
- Packed with shock-absorbing material
- Evidence labels and chain of custody included
➤ Miscellaneous Evidence
- Firearms packed in rigid containers, unloaded
- Clothing folded minimally and sealed
Searching of Physical Evidence at a Crime Scene
➤ Biological Evidence
- Use of visual search for blood, semen, or body fluids
- Alternate light sources (ALS) or chemical agents (like luminol) to reveal hidden stains
- Prioritize areas near the body or signs of struggle
➤ Chemical Evidence
- Search areas for drug packaging, burn marks, residues, or containers
- Portable detection kits used for preliminary analysis
- Use protective gear during search to avoid contamination or exposure
➤ Physical/Impression Evidence
- Careful inspection of entry and exit points, doors, windows, and surfaces
- Look for tool marks, fingerprints, and footwear impressions
- Use of oblique lighting to spot impressions
➤ Trace Evidence
- Use of lint rollers, tape lifts, and forensic vacuums
- Examination of suspect’s clothing, furniture, or contact surfaces
- Careful lighting and magnification often required
➤ Digital Evidence
- Locate devices such as phones, hard drives, and USBs
- Be aware of devices hidden in plain sight (e.g., disguised as other objects)
- Ensure proper digital crime scene protocols are followed
➤ Miscellaneous Evidence
- Search for documents, weapons, and personal items
- Look in drawers, closets, under beds, or buried areas
- Items evaluated based on relevance to the crime
Chain of Custody
➤ Definition
The documented process that records the seizure, custody, control, transfer, analysis, and disposition of physical evidence
➤ Key Elements
- Evidence labelled and sealed at the scene
- Each transfer recorded with time, date, and name
- Evidence never left unattended or unsealed
- Chain must be unbroken from collection to courtroom
➤ Importance
- Maintains legal integrity of the evidence
- Prevents tampering, loss, or substitution
- Required for admissibility in court
Physical Evidence in Different Crime Scene Contexts
Hanging
Physical Evidences:
Ligature mark: Pattern, position, and depth on the neck.
Rope/ligature: Type, knots, position.
Suspension point: Beam, ceiling fan, tree branch, etc.
Body posture: Feet touching ground or not (partial vs complete hanging).
Saliva dribble: Common in suicidal hanging.
Hyoid bone fracture: More common in manual strangulation (homicide).
Scene disturbance: Signs of struggle or tampering.
Suicide note, if any.
Footwear or prints near the hanging site.
Burning (Fire/Arson/Immolation)
Physical Evidences:
Burn patterns on the body and surroundings.
Accelerants: Petrol, kerosene (detected by GC-MS).
Container or matchsticks: Used to ignite fire.
Soot in airways: Indicates whether the person was alive during burning.
Charring levels: Helps determine exposure duration.
Position of the body: Defensive wounds suggest struggle.
DNA from partially burnt body.
Fire debris analysis for explosive residues.
Footprints or tire marks if arsonist fled the scene.
Drowning
Physical Evidences:
Froth around nose and mouth.
Water in lungs and stomach.
Diatoms test: Microscopic algae present in organs (confirms drowning).
Debris on body/clothing: Algae, mud, or plant matter.
Clothing analysis: Torn or displaced clothes may suggest foul play.
Defense injuries or blunt force trauma.
Water samples from the scene for comparison.
Hit & Run
Physical Evidences:
Vehicle parts: Glass shards, paint chips, plastic fragments.
Tire tread marks: May be matched to a specific vehicle.
Blood, hair, fibers on vehicle or at scene.
Injuries on victim: Patterned abrasions or lacerations.
CCTV footage from nearby areas.
Skid marks and drag patterns.
Clothing fragments or footwear of the victim.
Firearm-related Crime Scenes
Physical Evidences:
Bullet casings and spent bullets.
Gunshot residue (GSR): On hands, clothing of suspect.
Entry and exit wounds on victim (direction, distance).
Trajectory analysis.
Weapon: Type, fingerprints, serial number.
Blood spatter patterns: Help reconstruct shooting.
Shell casing patterns: Semi-auto vs revolver.
Surveillance footage, if available.
Drowning-Related Scenes
Potential Forensic Evidence:
Fluid accumulation in the respiratory tract or gastric cavity
Diatom analysis in bone marrow or internal organs as proof of active drowning
Personal effects (e.g., jewelry, torn clothing) suggesting foul play or resistance
Trauma indicators unrelated to water immersion (blunt force injuries, fractures)
Blood or tissue samples for toxicological screening
Forensic Significance: Helps determine drowning as cause of death, and differentiate between accidental submersion, suicide, or forced drowning scenarios.
Hit & Run
Physical Evidences:
Vehicle parts: Glass shards, paint chips, plastic fragments.
Tire tread marks: May be matched to a specific vehicle.
Blood, hair, fibers on vehicle or at scene.
Injuries on victim: Patterned abrasions or lacerations.
CCTV footage from nearby areas.
Skid marks and drag patterns.
Clothing fragments or footwear of the victim.
Firearm-related Crime Scenes
Physical Evidences:
Bullet casings and spent bullets.
Gunshot residue (GSR): On hands, clothing of suspect.
Entry and exit wounds on victim (direction, distance).
Trajectory analysis.
Weapon: Type, fingerprints, serial number.
Blood spatter patterns: Help reconstruct shooting.
Shell casing patterns: Semi-auto vs revolver.
Surveillance footage, if available.