Welcome to another edition of It’s in the Details, a short newsletter intended to provide helpful information for those in the litigation industry who deal with forensic engineering experts and their work.
What’s Your Expert’s Source for Aerial Photos?
Many experts, and even their clients and laypeople, have access to free online sources for aerial photographs. Google Maps, Google Earth, Bing Maps, Apple Maps, and USGS are prime examples. Such imagery can be used to understand how an incident site has changed over time, or to provide a backdrop for a computer simulation of vehicle motions leading up to a crash, for example.
These free resources have limitations, though, including being imaged infrequently, not having a specific date associated with them, or being low in resolution. This is where a service like Nearmap shines. Unlike many of the free services which use high altitude satellite photography taken only occasionally to generate their images, Nearmap uses a fleet of low-flying aircraft which scour major metropolitan areas every several months (sometimes half a dozen times a year!) to generate high resolution aerial images
A recent case of ours that went to trial highlighted the difference in outcomes between using the best available imagery from Nearmap in conjunction with computer simulation (as our firm did) versus simply presuming that the hand measurements in a police report were correct and then doing some rough manual calculations (like the opposing expert did).
Responding officers took very few scene photos, almost none of which depicted the tire marks left by the vehicles leading up to the crash. However, a Nearmap image taken only three weeks after the collision (shown below) depicted the locations of tire marks generated by the involved vehicles as they slid across the painted lines on the pavement, as well as fluid stains left by one of the vehicles. The presence of these items in the Nearmap image allowed us to confirm the vehicle rest positions as well as the distances and paths over which the vehicles had slid.
The opposing expert? His hand calculations significantly undervalued the post-impact slide distance of the vehicles, thereby greatly underestimating the impact speed of his client's vehicle. Black box data from the striking vehicle which came out later during discovery confirmed that the Dial-reconstructed impact speed based on the Nearmap evidence was good to within 1 mile per hour. And with that revelation, the opposing expert was not even called to testify at trial, and our client prevailed in his case.
Hopefully, this month’s newsletter has you confirming that your expert is investing in the digital tools required for accurate collision reconstruction and courtroom presentation. Thanks for reading, and feel free to reach out to us with any technical questions you might have about this or other topics related to forensic engineering.