by Gilson Penny

Created on: December 05, 2008   Last Updated: December 15, 2008

In the aftermath of an accident, confusion and memory discrepancies inhibit causal investigations. Forensics provides the key to recreating the event.

The first thing a forensic expert looks for at a crash scene, is whether any of the vehicles have been moved from their post-crash positions, and if so, how. In a catastrophic accident, all vehicles will generally remain in the positions they resulted in; however, in minor accidents, often the vehicles have been moved to the break-down lanes, so evidence is scattered between vehicle damage, skid marks, and re-positioned location.

The second item reviewed is the damage to the vehicles, to determine the points of impact and the extent of crush levels and secondary impacts, such as impacts from secondary hits in vehicle spin activity. This might involve vehicles hitting in multiple locations, or multiple vehicle impacts. All vehicles currently have crash test impact statistics available to forensic investigators, and the characteristics of crash impacts are frequently compared to test subjects.

The third item reviewed is location and environmental data. This would include weather and environmental impacts such as water, wet leaves, snow or ice, excessive sand, construction, or poor road conditions.

Fourth, evidence of skid marks is analyzed. The measurement of the position and length of the marks, and analysis of the engineering physics of the braking systems of the specific vehicles involved (provided by the manufacturers) vs. the evidence of the skid length and angle are calculated to determine the speed of the vehicles at the time of the crash and the braking characteristics applied by the driver during the crash.

Fifth, if injuries are reported, information such as seat-belt usage and chest trauma are analyzed, as well as any directional blunt trauma injuries to the victims (generally head and/or shoulder), and blood trails within the vehicles and outside of the vehicles are analyzed. DNA evidence is generally taken in multi-vehicle or multiple trauma crashes, to ascertain both victim identity and to eliminate potential for accident-scene tampering.

Between gathering the physical evidence at the accident scene, analyzing the manufacturing characteristics of the vehicles in terms of how their physical performance conforms to the accident scene evidence, and analyzing how the eyewitness accounts corroborate the forensic evidence, police can most often recreate a crash scene with striking accuracy.

Forensic science combined with Physics forms a solid view of an accident scene. This is often much more useful than eyewitness accounts, due to variances in speed perception, and emotional trauma. However, eyewitness accounts are always considered in combination with forensic evidence.

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