Traffic Crash Reconstruction Technology
The reconstruction unit has pursued new technology aggressively over the past several years. New technology has become available to make the reconstruction specialist's job easier, faster, more accurate, and safer. New technologies implemented include the use of Total Stations and CAD Software as part of a Forensic Mapping System for the recording of evidence, the use of computers for analysis, and the use of 3-dimensional animation for court presentation.
A total station is a combination of an Electronic Distance Measuring Instrument (EDMI) and a theodolite – an instrument that measures vertical and horizontal angles. The total station is set up at the crash (or other crime) scene to be measured and a reconstruction specialist holds a pole with a reflective prism at a point of evidence. The reconstruction specialist then takes a measurement, or 'shot', by pressing a button on a data collector. An infrared beam is emitted by the total station and is reflected back by the prism to the instrument. The reconstruction specialist enters a code for the specific 'shot', moves to another evidence location, and the process continues until the entire scene has been measured or “mapped”. The data collector records the distance, vertical and horizontal angles, and elevation for each 'shot' (evidence point) and displays the points on a small screen. Department reconstruction specialists currently use Leica TS12 robotic total stations coupled with Leica CS15 data collectors. A robotic total station automatically tracks the movement of the prism, eliminating the need to have a person stand at the total station and physically aim it at the prism. This model of total station is accurate to 1/8 inch over a quarter mile for distance measurements.
After the scene has been mapped the data from the data collector is downloaded into a CAD program and a scale diagram of the scene is generated. The scale diagram is then used by reconstruction specialists to further analyze the crash and assist in determining what exactly occurred, or, “reconstructing” the crash. One aspect of a reconstruction might be determining the approach and departure angles of vehicles, which, in conjunction with other factual information, can be used to determine the speed of the vehicles when they collided. During court testimony, the scale diagram of the scene is used to assist a jury in understanding the events that occurred. Reconstruction specialists currently use ARAS 360 software which is designed specifically for crash and crime scene reconstruction. In addition to the drawing component the software has very powerful calculation and animation capabilities to assist in a thorough analysis and reconstruction.
The use of a total station for measuring a scene and CAD software for generating a scale diagram is referred to as forensic mapping. Studies conducted by the states of Washington and Kentucky determined that use of the total station for measuring crash scenes allowed officers to record one-third more data points in about half the time it took to measure by hand. Typically, using the total station saves between 1 and 2 hours of measuring time per scene. In addition to the time-savings in measuring, the crash scene is safer for the officer and has less traffic congestion and fewer road closures. Also, considerable time is saved in completion of the scale diagram as compared to drawing it by hand. The final result is a reconstruction that is based on more accurate measurements and a scale diagram which takes less time to complete.
Once the reconstruction specialist has completed the investigation, testimony in court is the next step. Traffic crash reconstruction cases can be difficult to describe to a jury and, depending on the individual case, can be highly technical in nature. The reconstruction specialist must explain the situation observed at the scene, how and when the data was collected, as well as the methodology used to draw conclusions and opinions about the crash.
New computer technology has allowed the reconstruction specialist to take court testimony one step further with the ability to create a 3-dimensional animation of the crash sequence. 3-D animation is nothing more than taking the completed reconstruction and transforming it into a moving picture.
Animations have been used for several years by private firms; however, the cost of creating animations is extremely expensive. The Michigan Department of State Police (MSP) recognized a need for computer animation to assist our department with criminal investigations and to also assist other departments in their investigations at no charge. Having this technology available to all departments throughout the state gives smaller departments that could not possibly afford the software and training access to state-of-the-art technology.
The MSP has been using 3-D animation in their investigations since 1995. Since MSP was the first law enforcement agency in Michigan to use computer animation in traffic crashes, certain precedents had to be established. The number one precedent was to get the animation itself admitted into court as evidence.
To get admitted, the reconstruction specialist not only has to be accepted as an expert in accident reconstruction, but also as an expert in computer animation. Once accepted as an expert witness, the reconstruction specialist has to explain the way in which the animation was created and how the scene evidence was incorporated into the animation. Everything seen in the animation has been calculated and documented by the reconstruction itself, then put into motion and placed onto a video tape for viewing. Various camera positions can be chosen to give a complete look at the dynamics of the crash.
The MSP received their first conviction using computer animation in July 1995 and several more convictions have followed. The animation is the concluding piece, one that ties all the evidence, photographs, diagrams, opinions, and conclusions together into one motion picture of how the crash occurred.
|Click on image for 3-D animation|