The use of alternate light sources provides a highly practical and efficient means of locating physical evidence at crime scenes. Fluorescent liquids are used to develop latent prints on porous surfaces such as paper and cardboard.įluorescent dyes are used to enhance latent prints developed using superglue fuming. The benefit here is that the ridges fluoresce brightly and when photographed, a multi-colored or confused background can be minimized to the point where it does not show up in photographs. Fluorescent latent print powders have the ability to make the latent residue on a surface fluoresce. When using fluorescent chemicals, latent fingerprint development can be greatly improved. But modern science has resulted in the development of chemicals that “make” objects fluoresce. Other uses of alternate light sources Indeed, many forms of physical evidence will fluoresce. Also, certain narcotics will fluoresce as will bone and teeth fragments. ![]() UV alternate light sources can reveal the following: seminal fluid, saliva and urine stains. So what can alternate light sources reveal? Although blood does not fluoresce, certain other physiological fluids will. You see, blood does not fluoresce by applying UV or visible blue light.īlood, even minute quantities that remain after clean-up, can be made to “luminesce ” that is, by spraying certain chemicals such as Luminol, BlueStar or Fluorescene on the various surfaces, blood will luminesce, or simply “glow in the dark”-and adding blue light is not necessary. Shazam! Blue-white stains appear all over the floors, walls and objects sitting around the crime scene! But in reality-this cannot happen. If you watch many of the TV “Cop” shows, you will see at some point those working a crime scene using a blue light in search of invisible blood (blood stains that were cleaned up). Detecting hidden blood stains in crime scenes No filtration is required to view UV fluorescence, but eye protection in the form of clear glass or plastic lenses is recommended. UV light, on the other hand, is invisible, but it produces visible fluorescence from certain objects and substances. This blocks the intense blue light but passes the weak fluorescence. For example: if the visible light beam is blue light, the filter must be orange in color. This fluorescence is much weaker in intensity than the light beam that created it, so to visualize the fluorescence, the crime scene technician must use filtration that blocks the visible light but passes the fluorescence. Fluorescence occurs when light of a certain color and light frequency strikes an object, and the object returns light of a different color and frequency. You see, certain materials possess a property called fluorescence. Merely shining a blue or other visible color light onto an object in and of itself does not show us much. Using these colors enhanced the ability to reveal an abundance of what would otherwise be invisible evidence. In the 1990s the availability of high intensity incandescent lamps slowly revolutionized alternate light source analysis of physical evidence since these machines, many weighing less than 20 pounds, could provide an intense light beam that could be passed through various filters covering from visible blue, green, yellow and red light. Portable lasers began to appear in the marketplace in the 1980s, but their usefulness was limited to mostly a single color of light. The “Mounties” pioneered the use of argon-ion lasers, but these expensive, cumbersome, bulky machines were impractical for use at crime scenes, so their use was limited to the crime lab. But in the 1970s the Royal Canadian Mounted Police (RCMP) added a new dimension to forensic examination of physical evidence. Although some forensic investigators would occasionally use ultraviolet (UV Black Light) to examine for crime scene evidence, white light was the mainstay. Over many decades, visible light sources were used during most searches of crime scenes. ![]() Alternate light sources, a much needed tool for CSIs
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |