Bite Marks

A bite mark, also known as a dental injury, is a physical mark or trauma caused by human teeth biting or chewing on a surface. Bite marks have been used in criminal investigations to identify the perpetrator (or biter) based on their dental characteristics. This exercise teaches you how to lift bite marks.

Objectives

Recognize bite marks left at a crime scene

Collect bite marks

Preserve bite marks

Label bite marks using evidentiary materials

Materials

Styrofoam drink cup

Bowl (disposable)

Fork

Measuring spoon (TBSP)

Clear packing tape

Graphite Powder*

Corn Starch

Soft brush (paint, makeup)

White paper

Envelope (legal)

Permanent marker

Personal smartphone with camera

Flashlight

PPE (Suggested)

Procedures

1. Prepare the Bite Mark Evidence: Prepare the bite mark evidence. Make bite marks in the top rim of a styrofoam drink cup. To get both the upper and lower teeth, flip the rim of the cup over and under. Make six bite marks as follows: front top (FT); front bottom (FB); left top (LT); left bottom (LB); right top (RT); and right bottom (RB). With a permanent marker, label each bite mark underneath with the shorthand.

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 Bite Mark: Angle a flashlight at the bite marks to enhance their visibility and observe details. Document any unique characteristics.

4. Photograph the Bite Marks: Use a camera to photograph the bite mark from different angles, including close-ups and overall views.

5. Prepare the Lifting Powder: To make the lifting powder, mix 1 tablespoon of graphite powder* with 1 tablespoon of corn starch in a small bowl using a fork.

6. Powder the Bite Marks: Take a soft brush (paint/makeup) and lightly dab it in the lifting powder. Shake off any excess. Slowly dust the surface with light up and down strokes. Use a flashlight to illuminate a bite mark. Lightly add more lifting powder to the bite mark to outline the impression. Take caution to add lifting powder slowly.

7. Prepare the Bite Mark for Lifting: Once the bite mark is adequately powdered, use a strip of clear packing tape to lift the print. To do so, place the end of the tape (sticky side down) to the left of the bite mark. Using an up and down motion with your finger, adhere the sticky side to the cup and without any wrinkles or air bubbles in the tape. Then, using back and forth (left to right) motions, smooth the tape down over the top of the powdered bite mark. Gently, smooth out the tape to ensure it adheres to the cup. Be sure to avoid touching the sticky side of the tape while performing this step.

8. Lift the Bite mark: To lift the powdered print, slowly peel up one end of the tape. Continue to slowly lift the tape until it is off the cup. A powder print should be visible on the clear packing tape.

9. Record the Bite Mark: Place the tape with the lifted bite mark onto a piece of white paper, bite mark side down. Label the bite mark on the paper using the same shorthand as noted above. Repeat this process until all bite marks have been lifted and recorded.

10. Secure the Bite Marks: Secure the bite marks by placing the white paper in an envelope. Seal the envelope by closing it and taping the envelope flap closed.

11. Label the Evidence: Label the envelope with your initials, date and time of the collection, from where the bite marks were obtained, and a brief description of the envelope’s contents.

Notes

For this exercise, you may also use cocoa powder or charcoal powder in place of graphite powder.