Evidence Collection Worksheet for 16-Year-Olds — Forensic Science Practice & Crime Scene Skills

Instructions

Read each section carefully and answer the questions to the best of your ability. This worksheet will test your knowledge on the fundamental principles and procedures for collecting evidence at a crime scene. Think like a crime scene investigator!

Part 1: Key Terminology Matching

Match the term on the left with its correct definition on the right. Write the corresponding letter in the blank space provided.

1. ____ Chain of Custody
2. ____ Physical Evidence
3. ____ Locard's Exchange Principle
4. ____ Trace Evidence
5. ____ First Responder

Definitions:

• A. The first police officer or emergency personnel to arrive at a crime scene. Their primary duty is to secure the scene and ensure safety.
• B. The documented, chronological record of every person who has had an item of evidence in their possession.
• C. Small but measurable amounts of physical or biological material found at a crime scene (e.g., hair, fibers, gunshot residue).
• D. The basic forensic theory that every contact leaves a trace, meaning perpetrators both take and leave evidence at a crime scene.
• E. Any object or material that can establish that a crime has been committed or can provide a link between a crime and its victim or perpetrator.

Part 2: Scenario Analysis

Read the following crime scene scenario and answer the questions that follow.

Scenario: You are a forensic investigator called to a residential burglary. The homeowners were on vacation. The point of entry appears to be a shattered sliding glass door at the back of the house. Inside, drawers have been pulled out and their contents dumped on the floor. A muddy footprint is visible on the light-colored kitchen tile. On a table near the broken door is a half-empty bottle of water that does not belong to the homeowners. The master bedroom has been ransacked, and an empty jewelry box is lying on the bed.

1. List at least five different types of physical evidence you would look for and document at this scene.


2. Describe the proper method for collecting the muddy footprint found on the kitchen tile.


3. The water bottle is a key piece of evidence. What specific forensic evidence might it yield, and how should it be collected to preserve that evidence?


4. Why is it critical to photograph the scene extensively before touching or collecting any evidence?

Part 3: True or False

Read each statement below and determine if it is true or false. Circle your answer.

1. True / False     All wet evidence, such as blood-stained clothing, should be immediately sealed in an airtight plastic bag to prevent contamination.

2. True / False     It is acceptable for investigators to eat or drink inside the secured perimeter of a minor crime scene.

3. True / False     Evidence from different locations within the same crime scene should be packaged in separate, clearly labeled containers.

4. True / False     The chain of custody begins when the evidence is presented in court.

5. True / False     Fingerprints found at a scene are always visible to the naked eye.

Part 4: Critical Thinking

In your own words, explain why maintaining the integrity of a crime scene (i.e., preventing unauthorized access and contamination) is the most critical foundation of evidence collection.

ANSWER KEY

Part 1: Key Terminology Matching

1. B - Chain of Custody
2. E - Physical Evidence
3. D - Locard's Exchange Principle
4. C - Trace Evidence
5. A - First Responder

Part 2: Scenario Analysis

1. Five types of physical evidence: (Answers may vary but should include items from this list)
   • Fingerprints (on the water bottle, drawers, jewelry box, door frame).
   • DNA (saliva from the water bottle, potential skin cells, blood if the suspect cut themselves on the glass).
   • Trace evidence (fibers from clothing caught on the broken glass, hair).
   • Impression evidence (the muddy footprint, tool marks on the door frame from forced entry).
   • Glass fragments (for comparison to any found on a suspect's clothing).
2. Collecting the muddy footprint: First, the impression should be photographed from multiple angles, including directly overhead with a scale (ruler) for reference. If the print is stable, it can be lifted using an electrostatic dust lifter or gelatin lifter. If it is a three-dimensional impression in thick mud, a cast would be made using dental stone. The tile itself could potentially be collected if lifting is not possible.
3. Water bottle evidence: The bottle could yield DNA from saliva around the rim and fingerprints on the bottle's surface. It should be handled carefully with gloved hands, touching only the bottom and top where evidence is least likely to be present. It should be allowed to air dry completely before being packaged in a paper bag or cardboard box to prevent moisture from degrading the DNA. It should be sealed with evidence tape and labeled.
4. Importance of photography: Photography preserves the original location and condition of the scene and the evidence within it. It documents the spatial relationships between objects. Once an item is moved or collected, its original context is lost forever. Photographs serve as a permanent record for investigation and for presentation in court.

Part 3: True or False

1. False. Wet evidence must be air-dried first in a controlled environment. Sealing it in plastic while wet will cause mold and bacteria to grow, which will destroy biological evidence like DNA.
2. False. Nothing should be eaten, drunk, or smoked within the crime scene perimeter, as this can introduce new DNA and other contaminants, destroying the integrity of the scene.
3. True. This prevents cross-contamination between pieces of evidence. Each item gets its own clean packaging.
4. False. The chain of custody begins the moment an item of evidence is collected at the crime scene.
5. False. Many fingerprints are "latent," meaning they are invisible and must be made visible using powders, chemicals, or alternate light sources.

Part 4: Critical Thinking

Maintaining crime scene integrity is crucial because every piece of evidence must be in its original, unaltered state to be considered reliable in an investigation and admissible in court. Contamination can occur in two main ways: by adding material to the scene (like an officer's DNA or fibers from their uniform) or by destroying evidence (like walking over a footprint). A compromised scene leads to compromised evidence. This can weaken the prosecution's case, lead to wrongful acquittals or convictions, and make it impossible to accurately reconstruct the events of the crime. Without scene integrity, the link between the evidence, the suspect, and the crime scene (as explained by Locard's Principle) can be broken or called into question.