In February 2012, we published Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach, which documents the Working Group's findings and recommendations, addressing issues such as the acquisition of impressions of friction ridge skin, courtroom testimony, laboratory design and equipment, and research into emerging methods for associating latent prints with exemplars. This Working Group assessed the effects of human factors on forensic latent print analysis and recommended ways to reduce the likelihood and consequences of human error at various stages in the interpretation of latent print evidence. ![]() In December 2008, we partnered with the National Institute of Justice to sponsor the Expert Working Group on Human Factors in Latent Print Analysis. These errors may be attributed to a variety of human factors that may affect the examiner, such as health problems, stress, inadequate training, or insufficient resources. It also includes pattern analysis, such as is used when evaluating handwriting, typewriting, and writing instruments.Įxpert Working Group on Human Factors in Latent Print AnalysisĪlthough courts have accepted latent fingerprint evidence for the past century, several high-profile cases have highlighted the fact that human errors can occur. We know that criminals can leave these traces behind them after they commit a crime, but how easy is it to detect them? And how do experts record them for later analysis? To read about preserving impression evidence, pry open the next page.Pattern and impression evidence includes any markings produced when one object comes into contact with another object, such as fingerprints, shoeprints, toolmarks, and tire treads. All of these tools leave distinctive marks that investigators can easily identify - almost as if the tool itself were leaving a fingerprint at the crime scene. Suspects typically use wire cutters, crowbars and screwdrivers to cut and pry their way into windows and doors. Lastly, tool marks are created when a tool comes into contact with another object or surface and leaves a significant impression. Further inspection, however, can reveal more - defects and wear on a tire tread caused by nails, gravel, patches and alignment problems can identify a unique set of tires. Initially, a tire mark can tell an investigator the brand of tire a criminal used, but that only narrows things down slightly. ![]() Tire marks work the same way as footprints, although tire marks are much easier to identify. Still, stains and other residue will leave two-dimensional marks and create a recognizable image.Ī forensic scientist analyzes tire tracks taken from the scene of a hit-and-run car crime. ![]() Carpet or grass, however, will rebound and regain a flat surface more easily, and an impression on these types of surfaces will only last a short time. If you've ever driven a car through the mud, you've probably seen the clear scar the tires have left in the earth. Shoe impressions on materials such as soil, sand or snow can produce a largely three-dimensional footprint. Unfortunately, residual static charges don't last very long and can be easily upset, so forensic experts rely more on the deformation of surface areas. Simply sprinkling fingerprint dusting powder over recent footprints will attract the powder to the charge and create a visual image of the impression. Perhaps most surprisingly, even clean, dry shoes can leave an impression on a hard surface by creating electrostatic charges. ![]() But several things happen when our shoes touch the ground. Unless we're tracking in mud or rainwater and making a huge mess, it's nearly impossible to see the traces we leave with each step. When we walk into a room, we're usually not thinking about our footprints.
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