Physical Evidence
Physical evidence refers to any material object that can
establish that a crime has been committed or link a crime to a victim or
perpetrator.
Nature of Physical Evidence
- Objective & unbiased (does not depend on human memory)
- Permanent (cannot forget like witnesses)
- Scientific in nature
- Can be individual (DNA, fingerprints) or class evidence (fiber, soil)
Types of Physical Evidence
1. Biological Evidence
- Blood, semen, saliva, hair, tissues, bones
- Used for DNA profiling
2. Non-Biological Evidence
- Weapons,
glass, paint, soil, documents
3. Impression Evidence
- Footprints,
tire marks, tool marks
4. Trace Evidence
- Small, transferable materials (Locard’s principle)
- Hair, fibers, dust, pollen
5. Digital Evidence
- Mobile phones, laptops, CCTV footage
Search Methods at Crime Scene
1. Line/Strip Method
- Investigators walk in straight lines
- Best for large outdoor areas
2. Grid Method
- Double line search (horizontal + vertical)
- More thorough
3. Spiral Method
- Circular inward/outward search
- Used when single investigator
4. Zone/Quadrant Method
- Scene divided into sections
- Best for indoor scenes
5. Wheel/Ray Method
- From center outward
- Rarely used (may miss evidence)
Chain of Custody
Definition
: Chain of custody is the chronological documentation showing the
seizure, custody, control, transfer, analysis, and disposition of evidence.
Importance
- Ensures integrity of evidence
- Makes evidence admissible in court
- Prevents tampering or contamination claims
🔹 Key Components
·
Unique ID number
·
Date & time of collection
·
Names & signatures of handlers
Trace Evidence
Trace Evidence refers to small samples of a substance, in
particular, finger prints, fibres, hairs, glass fragments, soils, gunshot
residue, paint chips etc.
Dr. Edmond Locard, founder of the Institute of
Criminalistics at the University of Lyon, France, showed their importance for
the first time. He gave the famous Principle known as Locard’s Exchange
Principle, which states that every contact leaves a trace which means
that the criminal will definitely leave a trace evidence at the crime scene.
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