Collision Reconstruction 101: Physical Evidence, Physical Evidence, Physical Evidence!

Physical Evidence


Steven M. Schorr, PE, Collision Reconstruction Engineer ::::
The foundation of any collision reconstruction is the application of the laws of physics to physical evidence left as a result of the collision. This is done in an effort to determine, if possible, how the collision occurred. The laws of physics do not change. As such, the variable in every reconstruction is the available physical evidence. It is that data which determines to what extent a vehicular collision can be reconstructed.
When teaching young engineers about how to properly reconstruct the collision, the mantra is always “always default to the physical evidence.” That is, when attempting to reconstruct a collision the first three items (pieces of physical evidence) one should look for include the:

  1. Point of rest positions of the vehicles and/or pedestrianst
  2. The damage to the vehicles and/or injuries to pedestrians
  3. And any debris and/or markings on, or around the roadway left as a result of the collision

These details are always the foundation of any collision reconstruction.
Frequently, engineers are asked …”isn’t testimony an important factor in your reconstruction?” The answer is that testimony is a secondary level of evidence since it can be accurate or inaccurate. From a reconstruction standpoint, testimony can be evaluated to see whether it is consistent with the physical evidence, but it is the physical evidence that is the foundation of the reconstruction.
It must be noted that in the absence of physical evidence, sometimes the engineer is asked to assume certain things based on testimony. If this is done, it is the responsibility of the engineer to make it clear that those assumptions are part of the overall reconstruction analysis.
Steven M. Schorr, PE, President of DJS Associates, is a Collision Reconstruction Engineer and can be reached via email at or via phone at 215-659-2010.

Categories: Collision / Accident Reconstruction | Steven M. Schorr


Have A Question About This Article or Want to Contact the Expert?

Request An Expert

Fill out the form below so we may refer an expert

Do you have a question for us? We’re here to help!

James Schmidt Expert Spotlight