How Impression Evidence Works

When approaching acrime scenewith the intention of recording impression evidence, the first thing forensic investigators are taught to do is to secure and preserve the area. Because impressions are easily disturbed and often overlooked, a scene filled with too many people walking around could quickly become worthless to someone looking for footprints.

Once a perimeter is secure, investigators walk inward, looking for impressions and reconstructing the events of the crime to the best of their knowledge. They try to determine important facts such as the direction of travel or the number of suspects at the scene. Speciallighting技术可以揭示隐藏的小鬼ressions, including the use ofoblique lighting. By shining a light source diagonally at the ground, not vertically, the ridges of an impression create shadows which alert investigators to disturbed and uneven surfaces. Photographs of discovered impressions are also taken for visual documentation.

Although impression evidence is extremely fragile, if left undisturbed it can remain for long periods of time. As long as a crime scene area isn't harmed by weather (mainly wind, rain and snow) or disturbance from other shoes, tires or tools, there are two major techniques experts use to gather impression evidence:

As available equipment and techniques for forensic science improve, many in the field are realizing the importance of impression evidence. Although easy to overlook and difficult to locate, footprints and other impression evidence left at the scene of a crime are typically even more prevalent than fingerprints, and they can provide important clues to mysterious cases. To learn more about the shadowy world of criminal investigation, step lightly to the next page.

Related HowStuffWorks Articles

More Great Links

Sources