Evaluation of Police Speed Analysis in a Criminal “Rollover” Case


Steven M. Schorr, PE ::::

Case Synopsis: An ATV being operated at night, on a dark, dirt roadway, in a mountainous area rolled over crushing and killing an occupant riding on the back of the ATV.  The vehicle operator and the right front passenger survived with minimal injuries.  The police opined that the vehicle rolled due to driver error, specifically excessive speed. The operator indicated that his speed was limited and the rollover occurred when he had to steer to the left due to a deer and, in doing so, “caught” the right front tire in a depression in the dirt roadway.  The police charged the vehicle operator with traveling at an excessive speed, resulting in homicide by motor vehicle charges.

Expert Analysis: The physical evidence left as a result of the collision included scraping to the ATV and a documented blood spot on the roadway.  No other data was collected from the scene.  The dirt roadway in the area of the blood spot was “pitted” and not smooth, showing numerous depressions and irregularities.  Because of the limited data, a full engineering reconstruction of the collision based on physical evidence could not be completed.  During the criminal trial, the reconstruction engineer explained to the jury that the necessary components to complete a reconstruction (i.e., the specific point of rest of the vehicle; markings on the roadway; the specific location where the vehicle began to roll; etc.) were not available in this case and, as such, any opinions with regard to the specific vehicle speed would therefore be speculative.  Further, the reconstruction engineer illustrated to the jury that while the physical evidence was inconclusive as to specifically how the collision occurred, the testimony of the defendant vehicle operator that he steered left, caught his tire in a depression, and rolled the ATV over onto the passenger side was consistent with the applicable laws of physics. 

Result: The jury found the defendant not guilty, citing the lack of foundation for the police opinions.

Categories: Case Studies


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