Forensic science is the application of science to law. In practice, forensic science draws upon physics, chemistry, biology, and other scientific principles and methods. It focuses on the recognition, identification, individualization, and evaluation of physical evidence. Forensic science is an essential part of the judicial system – providing scientific information to investigators and the courts.
Forensic Scientist Edmond Locard (1877-1966) formulated the Locard’s Exchange Principle, which states that “with contact between two items, there will be an exchange”. Applied to crime scenes, perpetrator(s) of a crime come into contact with the scene, and the perpetrator(s) will leave something at the scene and take something from the scene. Every contact leaves a trace.
“Wherever he steps, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him. Not only his fingerprints or his footprints, but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects. All of these and more, bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent. Only human failure to find it, study and understand it, can diminish its value.”
—Paul L. Kirk. 1953. Crime Investigation: Physical Evidence and the Police Laboratory
Careers in Forensic Science
Forensic scientists are employed by: regional, state, and local forensic laboratories; district attorney’s offices; private firms; colleges and universities; the military; and, federal agencies (FBI, DEA, CIA, Secret Service, etc). There are several general career areas and disciplines:
- Biology – DNA Profiling, Paternity Testing, Forensic Biology
- Chemistry – Toxicology, Drug Analysis, Fire Debris & Explosives Analysis, Chemical Trace Evidence
- Crime Scene – Crime Scene Investigation, Crime Scene Photography
- Digital Forensics – Digital Examination, Information Security, Criminal Investigation
- Comparative Sciences – Questioned Documents, Fingerprints, Firearms/Toolmarks, Microscopy