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Notes for the Instructor

A fingerprint is the impression of lines and patterns made by a person’s fingertip. Fingerprints are a great way to tell people apart. Everyone’s fingerprint is unique. No two people in the world have the same fingerprints, even identical twins. We identify people in many different ways, such as their hairstyle and hair color. We might identify someone by describing his height, weight and eye color. But as a person gets older, many of these factors may change. Our fingerprints always remain the same.

The use of fingerprints for identification was presented late in the 19th century by the British scientist Sir Francis Galton. He developed a new classification system using prints of all ten fingers. This is the core of the identification systems still used today. In the United States, the New York State prison system was the first to begin fingerprinting all of the criminals that entered its doors. The U.S. Army began using fingerprints in 1905.

You leave a fingerprint behind on almost everything you touch. Sometimes the fingerprints are visible, such as those left behind when someone’s hand is covered in a substance like paint, dirt, or blood. Many other times fingerprints are invisible to the naked eye, or latent. Latent prints are the result of your hand’s natural oils or sweat being left on the surface you touch. Latent prints can be dusted with powder to reveal the print and fingerprint pattern.

Dactyloscopy is the study of using fingerprints to identify someone. To make a set of fingerprints, the ends of the fingers are inked and then rolled one by one onto a Ten Card. In this lesson, each student will make copies of his or her fingerprints and analyze the ridge patterns produced. Fingerprints from our four suspects involved in The Cookie Jar Mystery will be studied and compared to a fingerprint found at the crime scene.

The activities in this lesson address Next Generation Science Standards practices of Planning and Carrying Out Investigations and Analyzing and Interpreting Data. In addition, they address Common Core Learning Standards. See the appendix on page 105 for more details.