Soil Analysis

Students investigate a “cold case” by analyzing soil samples from suspects and a crime scene. Using observations of color, texture, structure, and pH, they determine which suspect’s soil matches the evidence.

1. Label soil samples from the crime scene and three suspects.
2. Place a small amount of each soil sample on a paper plate.
3. Use the Munsell chart to identify soil color; record results.
4. Test texture by feeling soil and using the soil triangle (sand, silt, clay proportions).
5. Examine structure (granular, blocky, platy, single-grained) and note any unusual features (roots, shells, fibers).
6. Prepare a vial with a small amount of soil, add distilled water, and gently invert.
7. Add universal indicator drops, wait a few minutes, and compare color to the pH chart; record results.
8. Repeat for all samples.
9. Compare crime scene soil properties with suspect samples to determine the best match.

Crime Scene Detectives: Soil Analysis - Chatty Zebra Curriculum:

📄 CSI: Forensic Soil Analysis - Soil Science Society of America: https://www.soils.org/files/sssa/iys/csi-activity.pdf

• Test soil from different local areas and compare their unique characteristics.
• Include unknown fibers or small debris in the samples for students to analyze.
• Extend by creating a “soil profile” with layered samples to show soil horizons.

• Do not taste or inhale soil or solutions.
• Handle glassware and pipettes carefully to avoid spills or breakage.
• Wash hands thoroughly after the activity.

• Why is soil unique enough to be used as forensic evidence? (Each soil has distinct color, texture, structure, and chemistry.)
• Which property—color, texture, structure, or pH—provided the strongest match? Why?
• What factors could cause soils from different places to look similar? (Similar parent materials, climate, or land use.)
• How might soil evidence be misleading if collected carelessly? (Contamination or mixing can give false matches.)