1. Unit #2 – Crime Scene Basics
Lesson #3 – Evidence Collection/Processing
Learning Goals
Know: Steps taken at the crime scene
Understand: Reasoning behind steps and precautions
Be Able To: Explain and perform basic crime scene investigation and evidence collection

2. Trace Evidence – The Search
The lead investigator will designate a search pattern appropriate to the crime and the scene.
Here are some options…
Inward/Outward Spiral
Parallel/Grid
Quadrant
A single investigator searches each quadrant. They may then switch quadrants and repeat.
A line of investigators searches in one direction. In a grid they then go in the other direction.
A single investigator starts on the inside/outside of the scene and slowly spirals out/in.
Good for areas that can be clearly cut into fours – square room, car, etc.
Good when the area is clearly defined and a lot of people are on hand.
Good for open areas or for scenes with limited number of investigators.

3. Trace Evidence – Collection Tools
We are finally ready to collect the evidence. Supplies you need…
Forceps/
Tweezers
Picking Up Evidence
Swabs
Evidence Tape
Vacuum
Gloves

4. Trace Evidence – Storage
Storing Evidence
Small trace evidence – HAIR, FIBER, SHELL CASING
Small envelopes
Plastic pill bottles
Small cardboard boxes
Glass vials
Use an appropriate container for
each piece of evidence

5. Trace Evidence – Storage
Storing Evidence
Larger evidence – WEAPON, DRINKING GLASS, CLOTHES
Manila envelopes (not white mailing envelopes)
Paper bags
Plastic bags
Wet or stained items – BLOOD, SEMEN, ETC.
Air-dry in non-airtight containers. Avoids molding.

6. Trace Evidence – Reference Samples
A piece of trace evidence is only useful if there is something to compare it to.
For example, a piece of hair from the scene can only be matched to other hairs.
Collect “reference” samples from:
VICTIM
SUSPECT(S)
OTHERS RELEVANT TO THE CASE

7. Other Trace Evidence
Examples of “other” trace evidence that may be discussed in other units include but are not limited to…
fingerprints
footprints/impressions
tool-marks
bullet holes
documents