When a structural, component or product failure leads to injury or death, a forensic engineer is close behind to investigate the root cause.

Engineers who studied the August 2007 I-35W bridge collapse in Minneapolis, Minn., that killed 13 people and injured 145 cited a steel gusset plate flaw from the structure’s original design in the 1960s.

After Hurricane Katrina’s deadly flooding of New Orleans in 2005, an independent levee investigation team from the University of California-Berkeley concluded that the poor performance of the flood protection system was due to engineering failures and questionable judgments involved in the levees’ design, construction, operation and maintenance.

But it isn’t only headline-grabbing disasters where forensic engineering principles apply. From construction accidents to faulty industrial machines, forensic engineers serve as expert witnesses in judicial proceedings related to failures, and their findings can lead to better design and testing of future creations.

Better Designs from Failure

Forensic investigations reveal why things fail. And from these failures, “engineers gain very important understanding and knowledge in order to help advance the technical competency of the field,” says Arthur Schwartz, executive director of the National Academy of Forensic Engineers (NAFE).

(Click to enlarge.) Sagging floors pulled external columns inward, eventually leading to the World Trade Center towers’ collapse in September 2001. This schematic shows the composite floor truss system. Image source: Wikipedia Indeed, acting upon the results of an investigation can create safer, more robust ways to test, design and construct materials, components, buildings, products and infrastructure. The building safety codes that changed following the collapse of the World Trade Center towers on Sept. 11, 2001, bring home this concept.

The National Institute of Standards and Technology (NIST) conducted an investigation of the catastrophe using thousands of photographs, 150 hours of videotape, 236 pieces of steel representing the different grades used in the towers, and extensive interviews with survivors and emergency personnel. Engineers and scientists then developed computer models of the aircraft impact, the evolution of the fires, how the steel weakened, and the progression of failures.

Investigators concluded in April 2005 that while the buildings were able to withstand the initial impact of the aircraft, the resulting fires weakened support columns and floors whose spray-on fireproofing was dislodged by the impacts. The sagging floors pulled the external columns inward, eventually leading to the towers’ collapse.

The NIST team listed 30 recommendations for improvements to building codes, regulations and practices. In September 2008, the International Code Council (ICC) approved 23 building and fire code changes based on these recommendations. Among them are increasing bond strength for fireproofing, along with revised field installation and inspection requirements; an additional exit stairway for buildings more than 420 feet high; and a minimum of one fire service access elevator for structures taller than 120 feet.

Michael Leshner, PE, a fellow of NAFE and the organization’s 2016 president-elect.Even on a smaller scale, forensic engineering can have significant influence. Michael Leshner, PE, a fellow of NAFE and the organization’s 2016 president-elect, once investigated a slip/fall incident at a fast-food restaurant where the outdoor tile walkway included a curb ramp with excessive slope at the slides, which was a code violation. Employees dragged trash through this area, leaving it greasy. A woman slipped and broke her hip.

Leshner some time later stopped at the restaurant and saw that the hazardous walkway was fixed. He cites the case as “a good example of closed-loop corrective action and successful application of engineering, law and responsible management.”

Just the Facts, Ma’am

The NAFE describes the professional practice of forensic engineering as "the application of the art and science of engineering in matters which are in, or may possibly relate to, the jurisprudence system, inclusive of alternative dispute resolution.”

Engineers cited a steel gusset plate flaw in the collapse of the I-35W bridge in Minnesota in 2007. Image source: WikipediaMost forensic engineers are professional engineers (PE) who are licensed under state law and who have developed expertise in a particular technology or industry. Attorneys, insurance companies, government agencies and businesses retain forensic engineers to analyze the causes of accidents and failures and perform accident reconstruction depending on the type of incident.

Samuel Sudler, PE, is a senior electrical engineer at forensic analysis firm S-E-A. Since 2002, he has assisted with 900 investigations related to alleged faulty electrical systems and controls. The role of the forensic engineer, he says, is to follow the scientific method in collecting and analyzing data. That entails going to the site of the incident. There he documents the scene with photographs, takes measurements, interviews individuals and confirms that the evidence matches with what the witnesses say. All this is done “so that the facts lead us in the right direction to find out what happened,” Sudler says.

Because engineers are engineers, they often find ways to perfect technology used in their own investigations. NAFE President John Leffler, PE, a forensic mechanical engineer with engineering consulting firm Forcon International, specializes in premises liability cases. When he started working on slip-and-fall cases 12 years ago, “testing of walkways had a bad reputation as junk science,” he says.

Leffler determined that the only way to offer defensible expertise was to make sure he had the best walkway traction test device on the market. “That led me to buy an existing design, totally reengineer it and prove it out,” he says. Leffler also is the primary author of ASTM F2948, “Standard Guide to Walkway Auditor Qualifications.”John Leffler, PE, Forcon International

Once they have conducted their research and analyzed the data, forensic engineers develop a hypothesis and check to determine that it is accurate to a reasonable degree of engineering certainty. Other responsibilities include preparing reports and studies, and testifying in depositions and trials.

Ultimately, the forensic engineer’s goal is to provide technical advice to the client so they can do their best to support their case, says Leshner.

Forensic engineers serve as expert witnesses on behalf of their clients, who typically represent a party in a lawsuit or in a claim that may become a lawsuit. Although most of the lawsuits are civil, forensic engineers occasionally become involved in criminal cases.

Because both sides hire forensic engineers, “opposing experts must be able to withstand a challenge and support their opinions under cross-examination,” Leshner says. “The other side will always question your expertise and try to attack your credibility.”

As with any engineering practice, forensic engineers are expected to follow high standards of professional ethics. It’s a topic that practitioners always should keep in mind, says Sudler. He is past chairman of the National Society of Professional Engineers (NSPE) Board of Ethical Review.

“As a professional engineer my main goal is to protect the health, safety and welfare of the public, no matter what,” he says.

However, on the occasion where the forensic engineer is a professional engineer who detects a safety hazard with the product or structure under evaluation, depending upon the nature and severity of the hazard, “our first obligation is to bring it to the attention of our client so they have an opportunity to address it,” Sudler says. He says that PEs have the obligation to guard against conflicts of interest with their clients. But if a hazard exists and the client isn’t taking corrective action, “then we would have to inform them we are reporting it to the proper authorities.”

A forensic engineering investigation, however, doesn’t always yield changes, or at least ones that are made public. “What happens frequently with litigation is that a flaw is uncovered, but the responsible parties will settle out of court and the experts’ reports or depositions are kept confidential,” says Forcon’s Leffler. “The extent to which cases end up in improvements through internal processes will vary.”

Delineating Qualifications

Forensic engineers generally need to have many years of experience and training to reach a status of an expert witness. But it is up to the legal system to determine the qualifications of the testifying practitioner on a case-by-case basis, says Ziad Salameh, PE, principal of consulting structural engineering firm ZS LLC.

Ziad Salameh, PE, vice chair of the forensic engineering division executive committee of the American Society of Civil Engineers. “It is not the duty, nor the responsibility, of our profession to actually qualify practitioners as forensic engineers,” says Salameh, who also is vice chair of the forensic engineering division executive committee of the American Society of Civil Engineers (ASCE). “It is too complicated for us to come up with certification program or ways of qualifying people.”

Although rules vary according to jurisdiction, expert witnesses typically are considered to be qualified by evidence of their expertise, training and special knowledge. If opposing legal counsel challenges the witness’s expertise, the attorney who is calling the expert to testify must demonstrate pertinent background through questioning. The trial judge has the discretion to qualify the witness or rule that he or she is not an expert, or is an expert only on limited subjects.

The NAFE, an affinity group of NSPE, was formed in 1983 to improve the practice and advance the cause of forensic engineering. Although NAFE does not define the qualifications of a practitioner acceptable to the court, the organization’s members, senior members and fellows are certified by the Council of Engineering Specialty Boards as “diplomates” in forensic engineering. To maintain their board certification, members must maintain 100 hours of continuing professional development during each five-year period.

A Growing Interest

Although becoming a forensic engineer is predicated on experience, college students and young engineers are making inquiries about the field. Salameh attributes the rising interest to the prevalence of high-profile structural failures, as well as the popularity of what he calls “Hollywood forensics,” in which television shows make the scientific method attractive.

Arthur Schwartz of NAFE says that he frequently receives calls from students and parents who want to know about preparing for a career in forensic engineering. In addition to the requisite math and science skills, he encourages students to plan for the testimony part of the job.

That means looking for “any opportunities that involve public speaking, preparing arguments, making presentations and being rigorously cross-examined or subjected to questioning,” Schwartz says.

Engineering colleges are responding. Columbia University recently launched a graduate-level forensic structural engineering concentration. The purpose is to provide students with the basics to investigate failures and understand the legal aspects, as well as to prepare students for the eventual practice of forensic structural engineering. The faculty, made up of full-time professors as well as practicing engineering, construction and legal professionals, also show students how to avoid failures and what the consequences of failures may be.

It’s not only the younger generation curious about the practice, however. Leshner knows many senior-level engineers in management positions who have moved toward forensic engineering “because they want to go back to the work they love and do best,” he says.