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Notes for the Instructor

Pattern evidence is any type of track or tread left behind at a crime scene that can be traced back to the item that made the print or impression. Common types of pattern evidence include shoe prints and tire tracks. In this activity, your students will explore pattern evidence by analyzing their own shoe prints and shoe prints left behind at the crime scene.

The type of shoe print left behind depends on (1) where the suspect’s shoes have been, (2) the type of surface around the crime scene, and (3) what type of shoe the suspect is wearing. Forensic scientists distinguish three types of shoe prints:

• Visible: a two-dimensional shoe print created when the shoe leaves behind a material, such as paint or mud, on a surface • Plastic: a three-dimensional shoe print created in a soft surface, such as sand or snow • Latent: a shoe print that is invisible to the naked eye, but can be revealed with chemicals or special lighting

For this lesson students will focus on visible, two dimensional prints.

First, students will make their own visible shoe prints using cardstock. Students will create a two dimensional print by stepping onto the paper with a damp shoe. The cardstock surface will be marked by the water and the dirt already present on the students’ shoes. As the water evaporates, the dirt from the shoe should remain visible as a print on the cardstock. Students will make observations about the size and pattern of their print. They will compare and contrast their print to a partner’s print. Students will also experiment by changing the amount of force or type of gait used to create the print.

Next, students will study the visible, two-dimensional shoe prints left behind on Mrs. Hawkin’s classroom floor. Students will try to match parts of a print to a larger pattern. They will also measure the length and width of the shoe print. Finally, students will make note of specific types of wear found in the print.

Please note that the shoe prints found at the scene will not match up with any of the suspect’s shoes. Very often investigators find evidence that doesn’t seem to fit within their current framework of understanding. Students should use this conflict of evidence to consider other possibilities. Are all of the suspects innocent? Is someone else involved with Alice’s disappearance? Are the shoe prints irrelevant to the crime?