Anyone with a television these days has probably seen forensic lighting at work. There's much to reveal in a crime scene, and the right lighting tools and techniques can make all the difference. Oblique lighting is one such technique, used to reveal hidden impressions. The most common and well-known types of impressions are, of course, footprints. These tend to be relatively large, deep and easily seen. Not all impressions are so easy to find, however, and these require special techniques, such as oblique lighting, to reveal them.
One of just a number of tricks crime scene investigators employ, oblique lighting uses what's called a forensic light source -- a lamp that breaks light into separate wavelengths to enhance visibility of various important things such as fingerprints, foot imprints and hair and fibers [source: crimescope]. Investigators shine the light on the ground obliquely, or diagonally, to spot shadows created by the ridges of an impression. The shadows alert crime specialists to the presence of disturbed surfaces that were otherwise hard to see. They can tell, for example, when someone has walked somewhere in a room, even if it might not be immediately clear to the naked eye.
Technicians use other lighting techniques as well, including fluorescent lights to make things glow and ultraviolet light, which is particularly suited to highlighting certain kinds of evidence. Meanwhile, powerful, white light does a good job of helping crime scene technicians see other hard-to-spot details, such as fibers, shoe prints and after-impressions left in dusty areas [source: Labino].
Another technique forensic scientists use to ferret out people trying to cover up a crime is handwriting analysis, or graphology, as it is sometimes called. Handwriting analysts need all the help they can get against the criminal element, especially when trying to sniff out simulation, which is the term used when a person either tries to copy someone else's handwriting or disguise his or her own handwriting to throw off attempts at analysis. Simulation can make accurate analysis very difficult, and sometimes impossible. But these analysts have their own tricks too. A professional handwriting analyst looks for several characteristics to determine if a piece of writing has been simulated. These characteristics include words with dark, thick starts and endings, shaky lines or frequent pen lifts -- all of which indicate the letters were slowly and carefully formed instead of written quickly and naturally.
With all of the emphasis on crime scene investigation in popular culture today (again, just turn on your television to any network in prime time), it's no surprise that the topic has garnered widespread interest from the public. While some law enforcement entities find it cumbersome dealing with the "CSI effect" -- unreasonable public belief in what crime science can achieve, and tons of requests for internships and tours -- one lab has take a different approach. Albuquerque, N.M.'s Metropolitan Forensic Science Center offers citizens a 10-week course in forensic science: "Introduction to Albuquerque Police Crime Scene Investigation" [source: Forensic Magazine].
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