Tool Mark Identification

Students create and examine tool marks in clay to learn how forensic scientists compare impressions and striations made by tools at crime scenes. By comparing known samples with unknown marks, they practice making positive identifications and ruling out mismatches.

1. Gather four tools, including two pairs of similar tools with slight differences (e.g., screwdrivers of different sizes).
2. Roll out dark modeling clay or Play-Doh into a flat surface.
3. Use one tool to make an impressed mark by pressing it into the clay.
4. Use the same tool to make a striated mark by dragging it across the clay.
5. Repeat with the other tools to create comparison samples.
6. Have a partner secretly choose one tool from each pair and create both an impressed and striated mark in fresh clay to represent a “crime scene.”
7. Examine the unknown marks and compare them to the known samples using visual inspection or a magnifying glass.
8. Decide which tool made each mark, making at least one positive identification and ruling out at least one tool.
9. Document findings with photos, sketches, and written notes.

Collecting Impression Evidence, pry marks and tool marks - Michael McCutcheon:

📄 Tool Mark Identification & Analysis Activity - Cliffs Notes: https://www.cliffsnotes.com/study-notes/26913053

• Test marks made in different materials, such as wax or soap.
• Use digital microscopes or cameras to enhance comparisons.
• Stage a mock “crime scene” where multiple students contribute tool marks for analysis.

• Handle tools carefully to avoid injury.
• Supervise use of heavy tools such as hammers.

• What is the difference between impressed marks and striated marks? (Impressed marks are indentations; striated marks are scratches or grooves made by movement.)
• Why is it important to test multiple characteristics of a tool mark instead of just one? (Similar tools may leave marks that look alike; detailed comparisons reduce error.)
• Can tool mark analysis always identify one specific tool? (Not always—sometimes it can only narrow down the possibilities.)
• How does this experiment model what forensic scientists do in real investigations? (They compare tool marks from crime scenes with suspect tools to determine matches or exclusions.)