Most people have heard of forensic medicine, which often involves examining a dead body to determine the cause of death and help identify the guilty party. Forensic engineering (FE), on the other hand, has to do with "dead" physical systems and specifically refers to the application of engineering to legal matters. FE is usually required because something failed, was misused, or was involved in an accident, causing injury or loss that resulted in a lawsuit. FE helps determine not only what happened, but why.
In a sense, FE deals with design "after the fact." It attempts to determine the physical factors that may be significant to the incident being litigated. We are all well aware of the old adage, "If it ain't broke, don't fix it." FE can be applied to fixing things that broke, or to improving a particular design so that it doesn't break in the same way again. Of course, it would always be better to improve design methodology so that things don't break in the first place. But no matter how carefully we design—and often in spite of the best of intentions and engineering effort—things break or go wrong.
In these cases, something may have been overlooked, substandard components or materials used, something misused, an unexpected environmental condition crops up, and so on. This is the nature of our world, due to the curse brought by Adam's disobedience. We should have no illusion that we will be able to eliminate failure and accidents through improved design. However, the application of our intellect to learning from trouble amounts to dealing with the "thorns and thistles" by the "sweat of our brow" that is our lot in life. Thus, we embark on a noble cause.
The phrase "experience is the best teacher" recognizes that we learn from things that go wrong, and we remember these situations best. For example, one of my design teachers related a story to the class about a toilet paper brand that never tore at the perforations, teaching us something about stress relief. Engineers applied the lessons learned here to improve aircraft design. Hopefully, we can learn something from FE that will help us improve design procedures, avoiding loss and litigation.
As I begin this series, my objective is to discuss the relationship of forensic engineering, more specifically application reconstruction, to design. As I review topics that come directly from my case files, you should learn some things that will make you a better designer and reinforce your understanding of the basic laws of physics.
In the coming months I will share stories and case reviews with you, wax philosophical, and have some fun in the process. I hope you will find this series worthwhile, entertaining, and—most important of all—educational in ways that will help you improve your own design work.
This report is the first in a series authored by Dr. Larry Zirkle, a forensic engineer who specializes in vehicular accident reconstruction. Director of special projects for TECH, a consulting firm that provides mechanical design and FE services, Zirkle is a former professor of mechanical engineering at Oklahoma State University. You can reach Larry at Lzirkle@mail.techok.com or email your comments to us at email@example.com.