Footwear Impressions

Footwear impressions are the marks left by the soles of shoes or boots at a crime scene. They can provide valuable information about the perpetrator, such as their size, shoe type, and tread pattern. In this exercise, you will learn how to collect footwear impressions from a crime scene using household materials.

Objectives

Recognize footwear impressions at a crime scene

Collect footwear impressions

Preserve footwear impressions

Label footwear impression evidence

Materials

Plaster of Paris (quick dry mix)*

Water

Measuring cup

Ziptop plastic bag (gallon size)

Aluminum pan (9"x13" or larger)*

Impressionable material (sand, dirt, baking flour) (4 cups)*

Personal smartphone with camera

Flashlight

Measuring tape*

Paper grocery bag

Clear packing tape

Permanent marker

PPE (Suggested)

Procedures

1. Create an Impression: Fill the bottom of a disposable aluminum pan (9"x13" or larger) with at least 4 cups of impressionable material such as sand, dirt, or baking flour. Put on a shoe or boot that will create a 3-D impression. Next, create a footwear impression in the pan by stepping in it; apply some weight when doing so. Allow the impression to set. If the impression is less than ideal, redo it by redistributing the impressionable material in the pan.

2. (Suggested) Put on PPE: To avoid contaminating the evidence and protect clothing, skin, and eyes, put on PPE including gloves, coveralls, headcover, and eye protection.

3. Illuminate the Impression: Angle a flashlight at the impression to observe its patterns and characteristics.

4. Photograph the Impression: Photograph the impression. This will document what the impression looked like before it is potentially disturbed.

5. Measure the Impression: Using a measuring tape, measure the length of the impression from the heel to the toe, as well as the width of the impression at the widest point; be sure not to disturb it. If the impression is clear enough, you can measure the ridge detail. This is the distance between the ridges on the sole of the shoe. Record all measurements on a piece of paper.

6. Prepare the Plaster Mix for Casting: Put on gloves. Pour two cups of Plaster of Paris in a gallon size ziptop bag. Next, add cold water according to the package instructions. Zip the gallon size bag closed. Mix the plaster and water together using your hands. The mixture should be of a thick, creamy consistency without any lumps. Do not mix for more than 2 minutes.

7. Apply the Plaster Mix: Carefully pour the plaster mix on the footwear impression. The plaster should be poured to the side of the impression, allowing it to flow over top the footwear print. If needed, a paint stick or disposable knife can be used to spread the plaster over the impression; however, be sure not to disturb it. Make sure plaster is evenly applied over the impression; a thin application is susceptible to breaking.

8. Allow the Plaster to Harden: Let the plaster mixture harden completely. This may take 30 minutes to several hours depending on the type of plaster mix used.

9. Remove the Cast: Once the plaster has hardened, carefully lift the cast from the impressionable material at both ends.

10. Secure the Impression: Secure the footwear impression by placing it in a paper grocery bag. Fold the top of the bag down to close it. Secure the fold by taping all the way around it.

11. Label the Impression: Label the bag with your initials, date and time of the collection, from where the impression was obtained, and a brief description of the bag’s contents.

Notes

If you do not have Plaster of Paris or cannot find it, you can use any casting material alternative. They can be found online and at craft and hardware stores.

In lieu of an aluminum pan, you may use a plastic rectangular container with similar dimensions.

If you use an aluminum pan larger than 9"x13", you will need more than 4 cups of sand or dirt.

For this exercise, you may use a ruler in place of a measuring tape.