Carnegie Mellon University

The Case of the Lipstick Litter: Teacher's Notes


  • Lipstick
  • Cotton Swabs
  • Plain Paper
  • Zip-lock Bags for "evidence"

Students should be given "evidence" in a plastic bag.  Suspect lip prints can be copied on a data sheet or the actual sample can be presented.

While lip prints are not as complex as fingerprints and are more easily' “typed", students will still need to have good observational skills.  If some of the lips have very distinctive shapes, students may pay more attention to the shapes than to the actual pattern on the lip surface.  Explain that lip shapes are not as unique as lip patterns are, and can't be used for identification.

When students try to prepare their own lip prints, the main problem is that they don't know how to blot lipstick properly, resulting in smears. Another problem may be poor application because they are using cotton swabs for sanitary reasons. Encourage students to liberally apply lipstick and then to blot in a single, quick motion.