Pinoy Crim
JurisprudenceLaw EnforcementCriminalisticsCrime DetectionSociology of CrimesCorrectional Admin
Practice Exams

Module 8.5: Evidence Collection, Preservation & Chain of Custody

I. General Principles of Evidence Collection

  1. Handle with Care: All evidence must be handled in a way that prevents any change from taking place between the time it is collected and the time it is analyzed in the laboratory.
  2. Wear Gloves: And change them often! This prevents the investigator from leaving their own fingerprints or DNA on the evidence.
  3. Package Separately: Each item of evidence must be packaged in its own separate container. This is the cardinal rule of evidence packaging. It prevents cross-contamination between different items (e.g., preventing fibers from a suspect's shirt from mixing with fibers from the victim's clothing).
  4. Use the Right Tools: Use clean, appropriate tools like forceps, swabs, and evidence vacuums. Avoid using your hands whenever possible.
  5. Create a Control/Reference Sample: For many types of evidence, a known sample must be collected for comparison.
    • DNA: A known DNA sample (e.g., from a cheek swab) must be collected from the suspect and the victim.
    • Paint: A sample of "un-transferred" paint must be collected from a damaged vehicle for comparison with a transferred paint chip.
    • Arson: A sample of unburnt carpet or wood must be collected from the same room as the suspected arson sample to serve as a control.

Packaging Summary

Evidence Type Recommended Packaging Why?
Bloody Shirt (Wet) Air-dry, then place in a paper bag. Breathable, prevents mold/DNA degradation.
Paint Chip Druggist's fold, then envelope. Prevents loss of small particles.
Revolver Unload, then secure in a cardboard box. Safety, protects prints and trace evidence.
Arson Debris Airtight metal paint can. Traps volatile fumes for analysis.
Ransom Note Plastic sleeve or paper envelope. Prevents damage and new markings.

Conclusion

The collection and preservation of physical evidence is a task that demands precision and diligence. There are no second chances; if evidence is contaminated, lost, or improperly packaged at the scene, its value is often lost forever. By using the correct techniques for different types of evidence and, most importantly, by meticulously maintaining an unbroken chain of custody, the investigator ensures that the physical evidence collected at the scene can survive the scrutiny of the legal process and serve its ultimate purpose: to speak the truth in a court of law.

Introduction

After a crime scene has been documented and searched, the next critical step is the collection and preservation of physical evidence. How evidence is collected, packaged, and preserved can make the difference between it being a crucial piece of a prosecutorial puzzle or an inadmissible item thrown out of court. This process is governed by strict procedures designed to prevent contamination, degradation, and any questions about the evidence's integrity. Central to this is the concept of the Chain of Custody, the unbreakable thread that links the evidence from the crime scene to the courtroom.

Key Learning Objectives:

  • Understand the basic principles of evidence collection.
  • Describe the proper packaging and preservation techniques for different types of evidence (biological, trace, firearms, etc.).
  • Define Chain of Custody and explain its critical importance.
  • Identify the information required on an evidence label and in a chain of custody record.

II. Packaging and Preservation of Specific Evidence Types

The type of packaging used depends on the type of evidence.

A. Biological Evidence (Blood, Semen, Saliva, Hair)

  • Problem: Biological evidence is susceptible to degradation by moisture, which promotes the growth of bacteria and mold.
  • Solution:
    • Evidence must be air-dried before packaging. Never use a hairdryer or heater.
    • Package in paper bags, manila envelopes, or cardboard boxes. These materials are breathable and allow any remaining moisture to evaporate.
  • NEVER use plastic bags for wet or moist biological evidence, as this will trap moisture and destroy the DNA.
  • Hair: Should be packaged in a "druggist's fold" or a small paper envelope.

Para sa biological evidence: PAPER, HINDI PLASTIC! Kasi ang plastic ay nag-trap ng moisture = bacteria = damage sa DNA. Air-dry muna bago ilagay sa paper bag. Parang damit na binabad - patuyuin muna bago ilagay sa laundry bag, hindi ba?

Board Exam Tip: Common mistake: Plastic bags sa biological evidence. Tama: Paper bags! Kasi breathable ang paper, hindi nag-trap ng moisture. Memorize: WET BIOLOGICAL = AIR DRY + PAPER BAG!

B. Trace Evidence (Fibers, Paint Chips, Glass Fragments)

  • Problem: This evidence is often microscopic and can be easily lost.
  • Solution:
    • Use a "druggist's fold" (a carefully folded piece of paper) to contain the sample before placing it in a larger envelope.
    • Use tape lifting for collecting fibers from a large surface like a carpet or car seat.
    • Vacuum sweepings can be used, but this is the least desirable method as it collects a lot of irrelevant debris.

C. Firearms and Ammunition

  • Problem: Preservation of fingerprints, trace evidence, and ensuring safety.
  • Solution:
    • Firearms: Must be handled by the edges of the grip or trigger guard to avoid smudging prints. The weapon must be unloaded for safety before transport. It should be secured inside a cardboard box, often using plastic zip ties to hold it in place.
    • Bullets and Cartridge Cases: Should be packaged in small, labeled boxes or envelopes. Never mark the bullet or cartridge case itself. Wrap them in paper to prevent scratching the microscopic striations.

D. Arson and Volatile Evidence

  • Problem: The evidence (e.g., a piece of carpet with gasoline) contains volatile chemical fumes that will evaporate if not properly contained.
  • Solution:
    • Package in a clean, unused, airtight metal paint can or a sealed glass jar.
    • This traps the volatile fumes inside, which can then be analyzed by the crime lab using headspace gas chromatography.

Para sa arson evidence: AIRTIGHT METAL CAN! Kasi ang volatile substances (like gasoline) ay nag-evaporate kapag exposed sa air. Kailangan mo i-trap ang fumes inside. Parang perfume - pag bukas ang bote, unti-unting nawawala ang amoy. Ganun din sa gasoline evidence.

Board Exam Tip: Arson Evidence = AIRTIGHT METAL PAINT CAN. Hindi paper bag, hindi plastic - kailangan metal can para ma-trap ang volatile fumes!

E. Questioned Documents

  • Problem: Damage from folding, moisture, or accidental markings.
  • Solution:
    • Place in a clear plastic sleeve or a properly sized envelope without folding it unnecessarily.
    • Do not write on the document or handle it excessively to avoid leaving fingerprints or indented writing.

Packaging Summary | Evidence Type | Recommended Packaging | Why? |

III. The Chain of Custody: The Unbroken Link

Definition: The Chain of Custody is a written chronological record of all individuals who have had possession of an item of evidence from the moment it was collected at the scene until it is presented in court.

Sa madaling salita, ito yung "paper trail" ng ebidensya - sino ang humawak, kailan, at ano ang ginawa. Parang relay race ng ebidensya - kailangan documented kung sino nagpasa kanino. Kapag may break sa chain, pwedeng ma-question ang integrity ng evidence sa korte!

A. Why is it Critical?

  • Foundation for Admissibility: For evidence to be admitted in court, the prosecution must be able to prove that it is the same evidence that was collected at the crime scene and that it is in substantially the same condition.
  • Preventing Tampering and Contamination: The chain of custody demonstrates that the evidence has been secure and has not been tampered with, altered, or contaminated.
  • A Broken Chain: If the chain of custody is broken—meaning there is a gap in the record where the location or handler of the evidence is unknown—the defense can argue that the evidence is unreliable and should be inadmissible. A broken chain can destroy the value of even the most compelling piece of evidence.

Bakit critical? Imagine may knife with blood sa crime scene. Pero walang record kung sino humawak from scene to lab to court. Pwedeng sabihan ng defense na na-plant lang yan or na-tamper. Kaya kailangan clear chain of custody - proof na secure ang ebidensya from point A to point Z.

Board Exam Tip: Chain of Custody = MOST TESTED CONCEPT sa CDI! Memorize: written chronological record ng lahat ng humawak ng evidence from scene to court. Pag may break, inadmissible ang evidence!

B. The Process

  1. Starts at the Scene: The chain begins with the officer who collects the evidence. They must record their name, the date, and the time.
  2. Sealing and Labeling: The evidence is packaged, sealed with evidence tape, and the collector signs or initials across the seal.
  3. Transfer: Every time the evidence changes hands, a transfer is recorded.
    • The person relinquishing the evidence and the person receiving it must both sign and date the chain of custody log or form.
    • This applies to transfers from the crime scene to the evidence locker, from the locker to the crime lab, between different sections of the lab, and back to the evidence locker.
  4. The Record: The chain of custody can be a separate form attached to the evidence package or can be part of the package itself. It must contain:
    • A description of the evidence.
    • The names of all persons who handled the evidence.
    • The date and time of each transfer.
    • The reason for the transfer (e.g., "for DNA analysis").

Board Exam Tip: The chain of custody is one of the most fundamental and frequently tested concepts in all of criminal investigation. You must understand what it is and why it is absolutely essential for the admissibility of evidence.