Lab Manual Teacher Guide
Crime Lab Manual
Internal Use Only // Setup & Key
Teacher Guide
Module: Trace Evidence - Soil & Glass
Activity Setup
Preparation
- Print the Evidence Station Cards (8 total stations).
- Laminate and hide the cards around the classroom, or place them in numbered envelopes.
- Distribute the Evidence Log Worksheet to each student or pair.
- (Optional) Place actual "mystery" samples (real soil/glass) in jars next to the cards for tactile analysis.
The Scenario
A burglary occurred at the Oakhaven Botanical Gardens. A display case was shattered, and the thief escaped through the rear greenhouse door. Detectives collected Crime Scene Samples (Soil S-1 and Glass G-1). Students must match these to samples found on three suspects.
Master Evidence Key
| Station | Type | Key Characteristics | Source |
|---|
| S-1 | Soil | Sandy, shell fragments, pH 8.0 (Alkaline) | Crime Scene |
| S-2 | Soil | Dark loam, high organic matter, pH 6.5 | Suspect 1 (Gardener) |
| S-3 | Soil | Sandy, shell fragments, pH 8.0 (Alkaline) | Suspect 2 (Matched) |
| S-4 | Soil | Clay, red tint, pine needles, pH 5.0 | Suspect 3 (Construction Worker) |
| G-1 | Glass | Soda-Lime, RI 1.51, Conchoidal fracture | Crime Scene |
| G-2 | Glass | Borosilicate (Lab glass), RI 1.47 | Suspect 1 |
| G-3 | Glass | Soda-Lime, RI 1.51, Conchoidal fracture | Suspect 2 (Matched) |
| G-4 | Glass | Lead Crystal, RI 1.56, Heavy weight | Suspect 3 |
Culprit Identified
Based on the trace evidence, Suspect 2 is the primary person of interest. Both their footwear (Soil S-3) and their clothing (Glass G-3) contain trace materials that chemically and physically match the samples found at the crime scene.
Confidential Case File // Forensic Lab Unit
Evidence Station Cards
S-1
Evidence: Soil (Crime Scene)
Visual Analysis
Light tan color, sandy texture. Visible shell fragments and high quartz content.
pH Test Result
8.0
Density Gradient
Layers settle primarily in the lower 20% of the tube (Heavy sand).
Serial: #772-CS
S-2
Evidence: Soil (Suspect 1)
Visual Analysis
Dark brown/black color. High organic matter (rotting leaves). Spongy texture.
pH Test Result
6.5
Density Gradient
Layers spread evenly; floating organic debris present at top.
Serial: #772-SUSP1
S-3
Evidence: Soil (Suspect 2)
Visual Analysis
Light tan color, sandy. Minute fragments of marine shell (calcium carbonate).
pH Test Result
8.0
Density Gradient
Heavy concentration in lower 20% of tube. Identical to beach sand profile.
Serial: #772-SUSP2
S-4
Evidence: Soil (Suspect 3)
Visual Analysis
Deep red-orange color, clay-heavy texture. Contains dried pine needles.
pH Test Result
5.0
Density Gradient
Fine particles remain suspended for hours; dark layer at bottom.
Serial: #772-SUSP3
G-1
Evidence: Glass (Crime Scene)
Fracture Pattern
Conchoidal fractures (shell-like curves). No radial or concentric cracks observed in fragment.
Refractive Index (RI)
1.512
Density Test (Flotation)
Fragment floats in a mixture of bromoform and bromobenzene (2.50 g/cm³).
Serial: #773-CS
G-2
Evidence: Glass (Suspect 1)
Fracture Pattern
Sharp, angular edges. Borosilicate composition. Heat resistant type.
Refractive Index (RI)
1.474
Density Test (Flotation)
Fragment sinks rapidly in the test mixture (2.23 g/cm³).
Serial: #773-SUSP1
G-3
Evidence: Glass (Suspect 2)
Fracture Pattern
Smooth, conchoidal ridges on break surface. Common soda-lime composition.
Refractive Index (RI)
1.512
Density Test (Flotation)
Fragment floats suspended in the test mixture (2.50 g/cm³).
Serial: #773-SUSP2
G-4
Evidence: Glass (Suspect 3)
Fracture Pattern
Evidence Log Worksheet
Evidence Log: Case #772-B
Agent:
Date:
Mission: Match samples S-1 and G-1 with suspect trace material to identify a forensic link.
Section 1: Soil Evidence
| ID | Visual Observations (Color/Texture) | pH | Density/Inclusions |
|---|
| S-1 | | | |
| S-2 | | | |
| S-3 | | | |
| S-4 | | | |
Section 2: Glass Evidence
| ID | Fracture Pattern Characteristics | RI | Density Profile (Float/Sink) |
|---|
| G-1 | | | |
| G-2 | | | |
| G-3 | | | |
| G-4 | | | |
Final Investigative Report
Matching Suspect: #________
Justification of Findings
Identify the matching sample IDs and explain how the forensic data supports your conclusion.
