Crash Investigation Unit (CIU)

Deputies who serve on the CIU have extensive training and expertise in crash investigation and crash reconstruction. Crash investigation and crash reconstruction are common terms, but what exactly are they, and what do they mean? After a motor vehicle crash occurs, particularly one resulting in severe injuries or death, it will usually be investigated and sometimes be reconstructed. The Sheriff's Office will investigate a crash with the intention of determining if any criminal action took place in the crash. 

Some of the things the CIU identifies are what caused the crash to occur such as:

• Driver Factors
• Environmental Factors
• Roadway Conditions
• Traffic Influences
• Vehicle Factors

Other parts of the investigation include what statute violations may have occurred such as hours-of-service violations, mechanical violations, alcohol and drug use, speed, no seat belt use, etc.

Crash Investigation Process

A crash investigation can consist of many aspects. The investigation usually begins with an inspection of the crash site. At the site, measurements are taken of evidence left by the vehicles are collected. These include point of impact, final resting positions, skid marks, gouge marks, etc. 

Measurements are taken using electronic surveying equipment. With this equipment, a computer-generated scale diagram can be produced and may be used to reconstruct the crash.

Vehicle Inspections

Vehicle inspections are a significant part of the crash investigation. These inspections include measuring the amount of damage including the damage profile of the vehicles. This information is useful if a crash reconstruction is performed. The mechanical components of the vehicles including brakes, steering, tires, suspension, lights, etc, may be inspected and tested to determine if the condition of these components were a causative factor in the crash. 

The investigation may include driver qualifications. CIU members may audit logbooks and review other motor carrier compliance materials.

Crash Reconstruction

With the crash investigation complete, a crash reconstruction can be performed. Reconstruction is the process of using physics to determine the speeds of the vehicles, and/or their relative positions at different times during the crash sequence. Information such as the following are all used as factors in the equations used to reconstruct a crash:

• Friction Values for the Various Surfaces the Vehicles Traveled Over
• Impact Angles
• Length of Pre-Impact Skid Marks
• Point of Impact
• Post-Impact Distances Moved
• Pre-Impact and Post-Impact Direction of Travel
• Weights of the Vehicles

Crash Data Recorder

Technology that assists the reconstruction team is the Crash Data Recorder (CDR) (black box) that is installed in newer vehicles. Downloading this information confirms data recovered at the scene. Currently, two team members are certified to interpret the data.