Engineering Analysis in Product Liability

Engineering analysis is a rather broad phrase that can include anything from a set of hand calculations to a complex state-of-the-art computer simulation. The rapid advancement of the personal computer and engineering software has led to the widespread use of commercially available engineering software to analyze just about anything.

Product liability cases typically involve a failed product. Making a determination as to how and why something failed requires a detailed failure analysis. These failure analyses can involve many different things. A sampling of issues that might be appropriate for a particular failure analysis could include:  chemical analysis, metallography, re-creation of the failure, destructive testing, non-destructive testing, materials testing, the environment in which the product was used, historical use of the product, potential misuse of the product, the basis for the design, engineering analysis, etc. Here we want to focus on engineering analysis because it is often something taken for granted. Conventional wisdom is often; “It came from the computer, it has to be correct, right?”

So, you have just started working a product liability case. Either your client or opposing counsel has relied on the use of engineering analysis to make a point. They may intend to demonstrate that the design is adequate or inadequate depending on their side in the case. As a non-technical expert it is difficult to determine what was adequate, what was needed, and if it was undertaken properly.

How or what can be done to sift through all of the information in order to make an assessment? First and foremost is to ask questions and take nothing for granted.

What types of questions should be asked? A sampling of questions is listed below.

• Who performed the analysis? How experienced are they in doing this type of analysis? Are they an expert at this type of analysis or did they perform the analysis because somebody had to do it?
• Did they use a commercially available software product? How experienced were they in using that software? Many of the new software products are very user friendly, but if the user selects the wrong option and effectively solves a completely different problem, the answer is flawed.
• Is the software designed to solve the type of problem being analyzed?  Yes – people do use the wrong software product at times and end up analyzing something completely different.
• How did they check their answer and make sure it was correct? Did they conduct an experiment to verify their results?
• Did they perform any other types of calculations to assist in demonstrating the validity of their results? Hand calculations can often be performed to bracket upper and lower ranges for a complex analysis. These simple calculations can assist in demonstrating that the detailed analysis is in the right range.
• Was the analysis they performed considered conservative? A “conservative” analysis is one that is based on more severe conditions. The concept is that if the analysis is conservative and the results still show that the product or part will survive the rigorous conditions specified in the analysis, then normal operating conditions should be acceptable. This is also sometimes referred to as a worst case analysis.

Above, I suggested that an inadvertent mistake in the use of a software product could lead to problems. You may say to yourself, “is this likely to happen?” It occurs far more often than people are willing to admit.

Several years ago I was working with a young engineer that was using one of the best structural analysis packages on the market to perform an analysis and interpret the results. In the process of discussing the approach and the results, the engineer made the following comment: “I can’t understand why when I change this one little boundary condition the whole answer changes.” The software was the best on the market, but the engineer’s understanding of how to use the product was inadequate.

Recently, a commercial client approached our firm to solve a very complex problem. They had designed a new product and the delivery deadline was rapidly approaching. As you can imagine, the parts were not ready to ship.  Part of the design process included the use of a structural analysis software package to assess certain aspects of the design. The analysis did not predict the trends they were seeing during testing. Why? Because incorrect assumptions were made in analyzing their design and the software was improperly used.

To the inexperienced user, the answers produced appeared reasonable.  The colors in the pictures looked smooth and pretty; doesn’t that mean everything came out ok? A quick look at the results by one of our experienced analysts indicated that the results were incorrect.

The examples cited above are not an indictment of engineering software or engineering analysis. On the contrary, these tools, properly used, can give great insight on a product design or clearly show an accident occurred. The flexibility of the software allows a proficient user to look at any number of scenarios and understand what might have caused or did cause the product to fail.

In a legal matter, technical experts often rely on the use of engineering analysis tools to support their opinion. It is critical to make sure they are experienced analysts and did their own due diligence in the process of completing their work.

As always, ask questions. Decide how important a particular piece of information is to your case, and react accordingly. The more important an engineering analysis is to supporting your case or refuting opposing counsel’s case, the more important it is to make sure every aspect has been addressed.

This article was written by Randy Clarksean, Ph.D., P.E., President of Kevin Kennedy Associates Inc. Randy has over 25 years of engineering, failure analysis and expert witness testimony experience. Randy can be reached at 317-536-7010 or via email at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .