In this lesson, students take part in the study of cheiloscopy [kahyl-los-kuh-pee]. Cheilo, from Greek, means lip. Cheiloscopy, therefore, is a forensic investigation technique that attempts to identify humans based on lip traces. Like fingerprints, lip prints are unique to each person and do change throughout our lives. This additional type of unique evidence is one more way forensic scientists are able to solve crimes.
Nevertheless, lip prints are not yet completely reliable in a courtroom. This is because they can be classified into one of eight patterns, and most people have a combination of at least two, leading to a great number of possibilities when identifying a print. The five most common lip prints patterns are: diamond grooves; branching grooves, like a plant; rectangular grooves, which might crisscross; short vertical grooves; and long vertical grooves.
Lip prints, like fingerprints, can be lifted from a glass or other surface for better examination. First, the investigator must place powder near a print, then spread it over the print with a very soft brush, so as not to damage it. Next, the print must be photographed. The print is covered with a piece of clear tape and then peeled off to actually “lift” the print. Now that the print has been lifted, it is available for comparison.
Students make and “lift” their own lip prints in the first activity. In the second, they use data from the entire group to create a graph. Using their knowledge of prints, they then examine the evidence on the envelope and match it to the suspects’ prints.
The activities in this lesson address Next Generation Science Standards practices of Asking Questions and Defining Problems, Planning and Carrying Out Investigations, and Engaging in Argument from Evidence as well as the cross-cutting concept of Patterns. In addition, they address Common Core State Standards CCSS.ELA-Literacy. CCRA. SL.1, CCSS.ELA Literacy.CCRA.SL.2, and CCSS. Math.Content.3.MD.B.3. See the Standards Matrix included in the appendix for more detailed information.