Unit 4: Collection and Packaging of Evidences at Crime Scene - Subjective Questions

Physical evidence refers to any tangible object, material, or substance found at a crime scene that can establish a connection between the crime, the victim, the suspect, and the location.

Significance in forensic examination:

• Establishes corpus delicti – proves that a crime has actually occurred.
• Links the suspect to the scene – through fingerprints, hair, fibers, or DNA.
• Links the victim to the suspect – via transfer evidence (Locard's Exchange Principle).
• Corroborates or refutes testimony – provides objective, unbiased information.
• Aids reconstruction – helps reconstruct the sequence of events.
• Identifies the modus operandi – reveals the method used by the offender.

Unlike testimonial evidence, physical evidence does not lie, does not forget, and is not influenced by emotion, making it highly reliable when properly collected and preserved.

Chain of custody is the chronological documentation showing the seizure, custody, control, transfer, analysis, and disposition of physical evidence from the time it is collected until it is presented in court.

Key elements documented:

• Who collected the evidence
• What the evidence is
• When it was collected
• Where it was found and stored
• How it was collected and preserved
• Every transfer of custody with signatures

Importance:

• Ensures integrity – proves the evidence has not been tampered with, altered, or contaminated.
• Establishes admissibility – courts reject evidence with a broken chain of custody.
• Provides accountability – identifies every individual who handled the evidence.
• Prevents challenges – protects against defense claims of contamination or substitution.
• Maintains authenticity – guarantees the evidence presented is the same as that collected.

A broken chain of custody can render otherwise valuable evidence inadmissible, potentially collapsing an entire case.

Collection of evidence must follow systematic principles to preserve its evidentiary value.

General principles:

• Document first – photograph, sketch, and note before touching any evidence.
• Use proper PPE – gloves, masks, and shoe covers to avoid contamination.
• Change gloves frequently – to prevent cross-contamination between items.
• Collect from least to most fragile – secure the most perishable/trace evidence first.
• Handle minimally – avoid unnecessary handling to preserve fingerprints and trace material.

Precautions:

• Use clean, sterile tools for each item.
• Never collect wet biological evidence in airtight containers – allow air-drying to prevent mold.
• Collect control/reference samples along with the evidence.
• Label each item immediately with case number, date, location, and collector's name.
• Avoid cross-contamination by packaging each item separately.
• Maintain chain of custody documentation from the moment of collection.

Adhering to these principles ensures the collected evidence remains admissible and scientifically reliable.

Biological evidence is fragile and prone to degradation, requiring careful handling.

Collection of Dried Bloodstains:

• On portable objects – collect the entire object.
• On immovable surfaces – scrape the stain into paper or lift with a moistened sterile swab.
• Always collect a control sample from an unstained area.

Collection of Wet Blood:

• Absorb onto a sterile cotton swab or gauze.
• Air-dry thoroughly before packaging.

Semen/Saliva:

• On clothing/fabric – collect the whole item, air-dry, wrap in paper.
• Use swabs for stains on skin or hard surfaces.

Packaging Rules:

• Never use plastic or airtight containers – moisture promotes bacterial and fungal growth that degrades DNA.
• Use paper bags, envelopes, or boxes which are breathable.
• Store liquid blood samples in refrigeration (not freezing) with anticoagulant (EDTA).
• Label with biohazard markings.

Forwarding:

• Transport biological samples in a cool, dry condition, ideally refrigerated.
• Maintain chain of custody and forward to the serology/DNA division promptly to prevent putrefaction.

Fingerprints are among the most valuable evidence for individualization.

Types and Collection:

• Patent (Visible) Prints – made by ink, blood, grease, etc.

  • Photograph with a scale before any further processing.
  • Collect the entire object if portable.

• Plastic (Molded) Prints – three-dimensional impressions in soft material like wax, putty, or soap.

  • Photograph with oblique lighting and a scale.
  • Preserve by collecting the object or making a cast.

• Latent (Invisible) Prints – require development.

  • Non-porous surfaces (glass, metal) – dust with fingerprint powder and lift with adhesive tape onto a backing card.
  • Porous surfaces (paper) – chemical methods such as ninhydrin, iodine fuming, or silver nitrate.
  • Cyanoacrylate (super glue) fuming for various surfaces.

Packaging:

• Lifted prints are mounted on lift cards and labeled with location and orientation.
• Portable objects are packed rigidly to avoid smudging, held so surfaces bearing prints are not touched.

Forwarding:

• Send to the fingerprint bureau with photographs and lift cards, maintaining chain of custody.

Firearm evidence requires special safety and preservation considerations.

Firearms Collection:

• Photograph and sketch the firearm in its original position before moving.
• Never pick up a firearm by inserting an object into the barrel – it damages internal striations.
• Handle by the checkered grips to preserve fingerprints.
• Unload safely, noting the position of cartridges in the cylinder/magazine.
• Record the serial number, make, and model.

Bullets and Cartridge Cases:

• Recover bullets from surfaces carefully – do not use metal tools directly on the bullet to avoid new striations.
• Wrap each bullet/cartridge in soft tissue paper individually.

Packaging:

• Place firearm in a rigid cardboard box, secured with strings/ties to prevent movement.
• Pack bullets and cartridge cases separately in labeled envelopes or boxes.
• Do not clean the firearm or barrel – residue is important evidence.

Forwarding:

• Forward to the ballistics division with details of make, caliber, and recovered projectiles, maintaining chain of custody throughout.

Different evidence types demand fundamentally different packaging to preserve integrity.

Key Distinction:

• Biological evidence deteriorates due to moisture and microbial action, so ventilation and cold storage are critical.
• Trace evidence (hair, fibers, glass) is at risk of physical loss and contamination, so it is secured in tightly sealed but appropriate containers such as paper bindles or plastic vials.

Using the wrong packaging (e.g., plastic for wet blood) can destroy the evidentiary value entirely.

Glass is common trace evidence useful for linking suspects to scenes and determining direction of force.

Collection Procedure:

• Photograph the broken glass and its distribution pattern.
• Collect all fragments, including tiny slivers, using forceps or a clean brush.
• Collect control samples from the broken window/object edges for comparison.
• Recover glass from suspect's clothing, hair, and shoes carefully.
• Note the inside vs. outside surfaces where possible.

Packaging:

• Pack fragments in rigid containers (film canisters, boxes) to prevent further breakage.
• Wrap large pieces in paper and secure in boxes.
• Pad small fragments to avoid puncturing and further fragmentation.
• Label each container with location and orientation.

Forensic Importance:

• Refractive index and density comparison links fragments to a source.
• Fracture matching (jigsaw fit) provides individualization.
• Radial and concentric fracture analysis determines the direction and sequence of impact.

Forwarding:

• Send to the physics/trace division with control samples, maintaining chain of custody.

Hair and fibers are important trace evidence supporting the Locard Exchange Principle.

Collection:

• Locate using oblique lighting and magnification.
• Collect individual hairs/fibers using clean forceps – avoid crushing.
• Use tape lifting for large surfaces or clothing.
• Vacuuming with a filter trap may be used for large area sweeps as a last resort.
• Collect known/reference samples from victims and suspects (pulled and combed hair).

Packaging:

• Place in paper bindles (druggist folds) or clean paper, then into labeled envelopes.
• Avoid loose plastic bags where static causes loss.
• Package each item separately to prevent cross-contamination.

Forwarding:

• Send to the trace evidence/biology division with reference samples for comparison, maintaining chain of custody.

Value:

• Hair reveals species, race, body area, and DNA (from root).
• Fibers reveal type, color, and manufacturing origin, linking a suspect to victim or scene.

Questioned documents include forged signatures, altered records, ransom notes, and threatening letters.

Collection:

• Handle with gloved hands and forceps, touching only the edges/corners.
• Do not fold, crease, or add new marks on the document.
• Do not staple, punch holes, or write on the original document.
• Photograph before collection with a scale.
• Collect known/exemplar samples of handwriting for comparison.

Packaging:

• Place the document flat between stiff cardboard sheets or in a transparent plastic/cellophane envelope.
• Do not clip or bind through the paper.
• Label the outside of the envelope, never the document itself.

Forwarding:

• Send to the questioned document examiner with exemplar samples.
• Preserve for examination of handwriting, ink, paper, indented writing, and alterations.

Precaution:

• Charred or wet documents require special humidification/handling and should not be forced open, being sent to experts intact.

Fire and explosion scenes require specialized collection to preserve volatile residues.

Arson (Accelerant) Evidence:

• Collect debris from the point of origin and burn patterns.
• Include charred wood, carpet, soil, and other absorbent materials suspected to contain accelerant.
• Collect comparison (control) samples from unburned areas.

Packaging for Arson:

• Use clean, airtight metal cans (paint cans) or special nylon/polyester bags.
• Airtight sealing is essential to prevent evaporation of volatile hydrocarbons (petrol, kerosene).
• Do not use ordinary plastic bags – they are permeable to hydrocarbon vapors and may react.
• Fill container only 2/3 full to allow headspace vapor analysis.

Explosive Residue:

• Collect residue from crater, debris, and surrounding surfaces using swabs.
• Package in airtight, non-reactive containers.
• Keep unexploded materials separate and handle only under expert/bomb-squad supervision.

Forwarding:

• Send to the explosives/chemistry division with control samples, maintaining chain of custody and safety protocols throughout.

Choice of container depends entirely on the nature of the evidence.

Paper Containers (bags, envelopes, bindles):

• Breathable – allow moisture to escape.
• Best for: biological evidence (bloodstained clothing), hair, fibers, and other trace materials.
• Advantage: prevents mold and microbial degradation of DNA.

Plastic Containers (bags, vials):

• Airtight and moisture-trapping.
• Best for: dry, non-biological items and liquids that must not evaporate; NOT suitable for wet biological samples.
• Risk: condensation promotes decomposition; static causes loss of trace evidence.

Glass/Rigid Containers (bottles, boxes, metal cans):

• Provide protection from breakage and vapor loss.
• Best for: glass fragments, firearms, liquids, and volatile arson accelerants (metal cans).
• Advantage: structural protection and vapor sealing.

Summary:

• Wet biological → paper (breathable)
• Volatile/arson → airtight metal can
• Fragile/sharp → rigid box
• Trace → paper bindle

Matching container to evidence type is essential to preserve evidentiary integrity.

A druggist fold (also called a paper bindle) is a specially folded paper packet used to secure small quantities of trace evidence.

Preparation Steps:

1. Take a clean sheet of paper (glassine or bond).
2. Place the trace evidence in the center.
3. Fold the paper into thirds lengthwise.
4. Fold into thirds again in the other direction.
5. Tuck the ends into one another to lock the packet.
6. Seal with tape and label the outside.

When it is used:

• For micro-trace evidence such as:
  • Hair and fibers
  • Paint chips
  • Glass slivers
  • Powders and soil
  • Gunshot residue particles

Advantages:

• Prevents loss of tiny particles through corners.
• Keeps evidence secure without static loss (unlike plastic).
• Can be placed inside a larger labeled envelope.

The bindle is then placed in an outer envelope which is sealed and labeled, and the chain of custody is documented.

Impression evidence records the physical characteristics of the object that made it.

Footwear and Tire Impressions:

• Photograph with a scale and oblique lighting first.
• Two-dimensional prints on hard surfaces – lift with electrostatic lifter or gel/adhesive lifters.
• Three-dimensional impressions in soil/mud/snow – cast using dental stone / plaster of Paris.
• For snow, use snow print wax before casting.

Tool Marks:

• Photograph with scale.
• Collect the entire object bearing the mark if portable.
• If not portable, make a silicone/casting-material cast of the impression.
• Never place the suspected tool against the mark – it may create new/misleading marks.

Packaging:

• Casts must be fully dried/cured before packaging.
• Wrap in paper or bubble wrap and place in a rigid box.
• Label without touching the impression surface.

Forwarding:

• Send casts and suspect tools separately to the tool marks/impression division to allow comparison, maintaining chain of custody.

Control (reference) samples are known, uncontaminated samples collected alongside questioned evidence for comparison purposes.

Importance:

• Enable comparison – questioned evidence is scientifically meaningful only when compared against a known standard.
• Establish baseline – account for background contamination from the substrate.
• Support individualization/exclusion – help match or eliminate a source.
• Strengthen court admissibility – demonstrate methodical, unbiased collection.

Examples:

• Bloodstain: collect an unstained portion of the same substrate as a substrate control, plus reference blood from victim/suspect.
• Glass: collect known glass from the broken window frame to compare with fragments on the suspect.
• Paint: collect standard paint from a vehicle to compare with transferred chips.
• Soil: collect soil from the scene and surrounding areas to compare with soil on a suspect's shoes.
• Fibers: collect known fabric from a suspect's clothing.

Without control samples, laboratory results may be inconclusive or inadmissible, since comparison forms the basis of forensic identification.

Drug and poison evidence requires careful handling for both chemical integrity and legal accountability.

Collection:

• Photograph and document all suspected drugs, powders, tablets, and paraphernalia.
• Weigh/count and record quantity where possible.
• Collect suspected poisons, vomit, food, or beverages in toxicology cases.
• In fatal cases, biological samples (blood, urine, stomach contents, viscera) are collected during autopsy.

Packaging:

• Solid drugs → paper envelopes, bindles, or plastic vials, tightly sealed.
• Liquids → clean glass/plastic bottles with leak-proof caps.
• Viscera for toxicology → preserved in saturated salt solution or refrigerated; a separate control preservative sample is sent.
• Avoid cross-contamination; package items separately.

Forwarding:

• Send to the chemistry/toxicology division.
• Include preservative details and control samples.
• Maintain refrigeration for biological toxicology samples.
• Strict chain of custody is critical due to the legal sensitivity of narcotics evidence.

Proper labeling and logging are the foundation of a defensible chain of custody.

Information on an Evidence Label/Tag:

• Case/FIR number
• Item number (unique identifier)
• Description of the item
• Exact location where found
• Date and time of collection
• Name and signature of the collecting officer
• Any initials/seal of the collector

Information in an Evidence Log/Register:

• Sequential list of all items collected
• Description and location of each
• Name of collector
• Every transfer – from whom, to whom, date, time, and purpose
• Storage location and condition
• Signatures at each transfer point

Role in Chain of Custody:

• Provides a traceable, documented history of the evidence.
• Proves the item presented in court is the same as collected.
• Demonstrates the evidence was secure and untampered.
• A missing or inconsistent entry can create reasonable doubt and lead to exclusion of the evidence.

These records make the evidence legally credible and scientifically reliable.

Cross-contamination is the unintended transfer of material from one evidence item, person, or surface to another, which can compromise the authenticity and interpretation of evidence.

Consequences:

• False associations between suspect, victim, and scene.
• Corruption of DNA/trace evidence.
• Loss of admissibility if contamination is proven.

Preventive Measures:

• Wear gloves and change them between each item.
• Use clean, disposable, or sterilized tools for each sample; use fresh tools per item.
• Package each item separately and seal immediately.
• Avoid coughing, sneezing, or talking over evidence (prevents DNA contamination).
• Wear masks, hairnets, and shoe covers.
• Do not collect known and questioned samples with the same equipment at the same time.
• Establish controlled access to the scene (single path in/out).
• Air-dry biological samples in a contamination-free space.

Strict adherence to these anti-contamination protocols preserves the scientific and legal value of the collected evidence.

Soil and botanical evidence can associate a suspect or object with a particular location.

Soil Evidence Collection:

• Collect soil samples from the scene and surrounding control locations at varying depths.
• Collect soil adhering to shoes, tires, tools, and clothing without dislodging it – package the whole object where possible.
• Note the exact location and depth of each sample.

Botanical Evidence Collection:

• Collect leaves, seeds, pollen, twigs, and grass found on the body or objects.
• Collect reference plant samples from the scene.
• Use forceps and handle carefully to preserve delicate structures.

Packaging:

• Soil → paper bags or containers; allow moist soil to air-dry to prevent mold.
• Botanical → paper bags/envelopes (breathable); avoid plastic for fresh plant material.
• Label with location and collection details.

Forensic Relevance:

• Soil comparison (color, texture, mineral, and biological content) links a suspect to a scene.
• Pollen and plant analysis (forensic palynology/botany) can indicate location and season, and detect movement of a body.

Control samples and proper drying are essential, and chain of custody is maintained throughout.

Forwarding evidence is the formal process of transferring collected items to the laboratory while preserving integrity.

Step-by-Step Procedure:

1. Proper Packaging – each item is packed in an appropriate container based on its type (paper for biological, cans for arson, etc.).

2. Sealing – containers are sealed with tape and the collector's initials/official seal are placed across the seal so any tampering is evident.

3. Labeling – each package is labeled with case number, item number, description, location, date/time, and collector's name.

4. Documentation – prepare a forwarding letter/memo listing:

   • All items being sent
   • The examinations requested
   • Relevant case history
   • Reference/control samples included

5. Forwarding Authority – evidence is sent through an authorized officer/messenger or registered means, never left unattended.

6. Chain of Custody Form – accompanies the evidence, recording every transfer with signatures, dates, and times.

7. Mode of Transport – biological/toxicological samples are transported refrigerated; volatile samples in sealed cans.

Key Requirements:

• Tamper-evident seals on every container.
• Separate packaging to prevent cross-contamination.
• Complete documentation and unbroken chain of custody.

Proper forwarding ensures the evidence reaches the laboratory in an uncontaminated, legally admissible condition.