Fingerprints

Fingerprints are unique impressions left by the friction ridges of a human finger. They are formed by the ridges and valleys on the skin of the fingers, palms, and toes, and may be used to identify suspects. This exercise teaches you how to lift fingerprints for analysis.

Objectives

Recognize fingerprints at a crime scene

Lift fingerprints from various surfaces

Secure fingerprints in evidence

Label fingerprints evidentiary materials

Materials

Aluminum drink can

Glass cup/bottle

Bowl (disposable)

Measuring spoon (TBSP)

Clear packing tape

Graphite Powder*

Corn Starch

Soft brush (paint, makeup)

White paper (computer/cardstock)

Envelope (legal)

Personal smartphone with camera

Permanent marker

Flashlight

PPE (Suggested)

Procedures

1. Prepare the Fingerprint Evidence: Prepare the fingerprint evidence. Apply fingerprints to an aluminum drinking can, glass cup, and/or glass bottle.

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 Fingerprints: Angle a flashlight at the fingerprint evidence to observe any fingerprint patterns and characteristics.

4. Photograph the Fingerprints: Before doing anything else, photograph the fingerprints. This will document what they looked like before they are potentially disturbed.

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

6. Powder the Fingerprints: Take a soft brush (paint/makeup) and lightly dab it in the fingerprint powder. Shake off any excess. Slowly dust the surface with light up and down strokes. Use a flashlight to illuminate any fingerprints. Once a fingerprint is identified, lightly add more fingerprint powder to the print, following the direction of the fingerprint ridges. Take caution to add fingerprint powder slowly so as to not erase the print.

7. Prepare the Fingerprint for Lifting: Once the print 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 fingerprint. Using an up and down motion with your finger, adhere the sticky side to the can/glass/glass bottle 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 fingerprint. Gently, smooth out the tape to ensure it adheres to the can/glass/glass bottle. Be sure to avoid touching the sticky side of the tape while performing this step.

8. Lift the Fingerprint: To lift the powdered print, slowly peel up one end of the tape. Continue to slowly lift the tape until it is off the can/glass/glass bottle. A powder print should be visible on the clear packing tape.

9. Record the Fingerprints: Place the tape with the lifted fingerprint onto a piece of white paper, fingerprint side down. Additional fingerprints from the same piece of evidence may be collected and transferred to the paper.

10. Secure the Fingerprints: Secure the fingerprints by placing the white paper in an envelope. Seal the envelope by closing it and taping the envelope flap closed.

11. Label the Fingerprints Evidence: Label the envelope with your initials, date and time of the collection, from where the fingerprints 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.