Detective Science: 40 Crime-Solving, Case-Breaking, Crook-Catching Activities for Kids Detective Science: 40 Crime-Solving, Case-Breaking, Crook-Catching Activities for Kids Detective Science: 40 Crime-Solving, Case-Breaking, Crook-Catching Activities for Kids Paperback Kindle

During the investigation of a crime, law enforcement officials collect evidence. This evidence, along with witness statements, is later used in courts to prove that a crime was committed and to convict the person or persons responsible for committing that crime. To convict means to find guilty, in a court of law, of committing a crime.

In 1910 at the University of Lyons, Edmond Locard first recognized the value of evidence to solve crimes and convict criminals. He developed a theory about evidence called the contact trace theory. This theory states that criminals will always take with them a trace of something from the scene of the crime, and will always leave behind some trace of having been there. The contact trace theory is the foundation of forensic science. The job of forensic science investigators is to locate the trace evidence, subject it to analysis and comparison in a forensic science laboratory, and then use all of the evidence to figure out what happened at the scene of a crime.

There are many ways to identify a person. One of them is cheiloscopy, or the study of lip prints. (The term cheiloscopy comes from the Greek word cheilos, meaning "lip.") Lip prints are unique and do not change during a person's life. Although they are less commonly encountered than fingerprints at the scene of a crime, lip prints found on glasses, cups, and even letters can be valuable evidence. One problem with lip prints is that their credibility has not yet been established in courts of law.

Lip prints are commonly classified into eight patterns. Four of the most common patterns are shown here.