From The Ergoweb® Learning Center

Forensic Ergonomics

The January 2011 issue of Ergonomics In Design: The Quarterly of Human Factors Application, a publication from the Human Factors and Ergonomics Society (HFES), is dedicated entirely to forensic human factors/Ergonomics (HF/E). This special issue is noteworthy for at least two reasons:

  1. It is very applied, detailing real HF/E forensic work in real legal cases; and
  2. The selection of articles covers the broad spectrum of HF/E practice, including physical cognitive and organizational applications.

Forensics is yet another area of practice through which ergonomists and human factors engineers contribute to making the world a better place. Forensics, according to dictionaries referenced at, is the art or study of formal debating, specifically pertaining to, connected with, or used in courts of law or public discussion and debate. More specifically, it relates to or deals with the application of scientific knowledge to legal problems.

As regular readers of The Ergonomics Report™ know, Ergoweb is a strong proponent of evidence based decision making and solution application, and a scientific basis for opinions presented in the court system is especially important in light of the Daubert Standard, which deals with the admissibility of scientific expert testimony.

In his introduction, Ken Nemire, the editor for this EID special issue, recognizes that:

Most human factors/ergonomics (HF/E) practitioners are involved with designing tools, tasks, jobs, systems, and environments for safe and effective human use. Forensic HF/E practitioners, relatively few in number, evaluate these designs (often, designs that did not result from HF/E expertise) and user behavior when they fail and litigation ensues. The results of forensic HF/E practitioner involvement not only aids attorneys, judges, and juries during the litigation process but also may help prevent similar incidents from happening in the future.

In the USA, the judicial/court system plays an extremely important role in advancing health and safety in product and process design. Not to dwell on the nuances of the USA system of government, but for the purposes of this topic do recall that there are three branches of government with different purposes and different abilities: judicial, legislative and executive. In theory, and sometimes even in practice, the structure provides a balance of power and a series of checks and balances among the different viewpoints, interests and agendas that compete in the pursuit of civil society. As it applies to this topic, the legislative and executive branches are characterized and heavily influenced by politics and tend to act on a shorter time frame and less rigorous analysis and understanding of a problem, while the legislative branch acts on the longer term and is far more concerned with provable facts.

A case in point: unintended vehicle acceleration. In his EID article, An Early (1969) Case of "Unintended Acceleration" Crash, Rudolf Mortimer details a court case that covered an accident involving a Cadilac Eldorado that unexpectedly accelerated in reverse, pinning a pedestrian between it and another car. HF/E experts were consulted by the attorneys on both sides of the case, and the judge and jury were therefore able to hear various evidence based opinions with regard to the vertical and horizontal separations between the accelerator and the brake pedals. In this case, General Motors, the defendant, prevailed. Moritmer provides a detailed review of the procedures, analyses, and conclusions from each expert, and interested readers are encouraged to read the full article, cited below.

But recall that unintended acceleration was also in the news in the 1980’s, when Audi faced a series of such claims, and again recently, as Toyota  faced similar claims. Ergoweb covered this topic briefly in an Ergonomics Today™ article (see Not So Fast — Toyota’s Unintended Acceleration), making the point that politicians from the legislative and executive branches quickly jumped to unfounded and unsupported conclusions, which were clearly influenced by ulterior political motives. Had these politicians prevailed, manufacturers and consumers could have been saddled with law that codified false logic and conclusions. As imperfect and time consuming as the courts can be, in this case, and in many other health and safety questions, we are better off leaving the forensics to the experts and relying on the court system to ferret out the truth, rather than taking the expedient, yet often false, counterproductive or unreliable track advocated by legislative and executive politicians, who in turn may be heavily influenced by special interests.

Take another example from the EID special issue on forensics, Fatality in the Side of a Bunk Bed, by Carol Pollack-Nelson. The article begins with a very sad story:

Ryan was just a few months shy of his fifth birthday when he died on the bunk bed where he was sleeping. When his mother last saw him, the night before, he was going to sleep in the lower bunk, with his 9-year-old sister sleeping in the upper bunk. In the morning, his mother went to awaken the children. It was then that she found Ryan with his neck caught between the vertical post of the side ladder and the mattress. His body was outside the bed, with his back to the mattress and his bottom on the floor. Ryan was already dead when his mother found him.

Pollack-Nelson describes how she applied anthropometric data to uncover a hazard and makes the point that had such an analysis been conducted prior to marketing the product, the hazard could have been detected and the accident prevented. She further argues that standards that cover design aspects to prevent head entrapment at either end of bunk beds should be updated to include entrapment potential for side structures like the ladder that played a role in this accident (ASTM, 1992, 2007; CPSC, 1999).

In Something Old, Something New, Something Borrowed, but Nothing Blew!, Robert Sugarman describes a legal case in which he was asked to investigate an accident that killed a railroad maintenance worker.

A three-person team of rail maintenance workers clearing a frozen switch were not aware that a rapid transit commuter train was approaching on their track. All the workers faced away from the approaching train. Two of them stood on either side of the track, and the third kneeled between the tracks working on the switch. The environmental conditions were nighttime and extremely cold.

My analysis of this accident started with the question, “Did the workers have sufficient time to escape from the track once they became aware of the train?” but it evolved to, “If the horn had blown, would the workers have had sufficient time to escape?” This was not a matter of simply determining the reaction time (RT) for the kneeling worker to stand up. This was a complex sequence of interdependent tasks and steps involving as many as four individuals, complex equipment, and challenging environmental conditions.

In his article Sugarman details how he utilized Methods-Time-Measurement (MTM-1) data to demonstrate for the court that the fatality could not have been prevented even if a warning signal — a blow of the train’s horn — had been given.

Organizational ergonomics, or macroergonomics as it has come to be known, is the central theme in The Role of Forensic Organizational Ergonomics, by Joseph Cohen. In this case, a female employed as a janitor sustained irreparable lung damage while working in a large medical center.

Attorneys representing the defendants alleged that Ms. White broke a rule on many occasions and acted unsafely by repeatedly mixing chemicals and should, therefore, bear responsibility for her injury. The attorney representing the plaintiff alleged that failures of management and design contributed to deficiencies in the work system, which unnecessarily allowed Ms. White opportunities to mix chemicals to keep up with the demands of her job.

Cohen describes the use of a macroergonomics model that recognizes that organizational factors, which are shaped by the organizational culture, influence the design of human-job, human-machine, human-environment, and human-software interfaces, can be linked to unsafe acts of individuals by managerial factors, supervisory factors, and psychological precursors. In this particular case, the ergonomics consultant was able to develop an explanation for the court that shifted blame that the defense had placed entirely on the injured employee to a scenario that recognized the injury had roots in systematic organizational failures, thus allowing the two parties to reach an amicable conclusion to the lawsuit.

Science certainly plays a critical role in forensic HF/E, but Richard Hornick, in his article Research of a Different Kind describes how small studies that might not otherwise appear to have scientific rigor may actually be very useful in the courtroom.

Indeed, in forensics work, a sample size of 1 might be of major significance, and rigid repetitive tests for analysis of variance may actually be ridiculous …

… Instead, the expert must be conversant with the existing research and be able to interpret it for the contested issues. And the expert might well conduct some kind of quick and limited experiment in support of his or her opinions and describe the results of both kinds of research so that judge and jury can understand them for establishing a reasonable degree of scientific certitude.

Hornick notes that the Daubert Standard places the burden on HF/E experts to indeed ground their fundamental testimony in sound science, but that quasi-experimental research … augments what HF/E science offers by way of elaboration or demonstration and provides supportive data for our opinions as well as data that otherwise may not exist in the literature. He provides examples that he has used in his own forensic work, including questionnaires relating to warning signs on a forklift, a comparative study testing the effectiveness of battery retention designs between various bathroom scales, and a bulldozer operational test in which it was demonstrated that the vehicle could be effectively operated with a guard protecting the controls from inadvertent activation.

Articles titled The Role of Physical Ergonomics in Litigation, Cognitive Human Factors in Litigation, and Failure to Detect gas Leaks: Forensic Human Factors Considerations round out this special issue by providing a wide variety of case examples where HF/E science and testimony played a key role in informing the judge and jury. In Forensic Ergonomics: Where We’ve Been and Where We’re Going, Harvey Cohen traces the history of HF/E forensics to the mid-1960’s, pointing to evolving government legislation and entrepreneurial pursuits by ergonomists in the private sector as the two main factors in the continued growth of forensics within the HF/E profession.

HF/E experts play a critical role in helping juries and judges understand the causal or contributing factors to accidents. This special issue of Ergonomics In Design is a great way to understand how our profession evolved to influence the judicial system, provides real-world examples of how HF/E experts participate, and gives thought to what the future may bring for HF/E in the courtroom. It is well worth reading if you have an interest in forensic ergonomics and human factors.



All of the articles described in this article are accessible in this special issue of Ergonomics in Design: The Quarterly of Human Factors Applications.

Ergonomics In Design: Forensics Special Issue, a publication of the Human Factors and Ergonomics Society, Number 1, January 2011, last accessed from on April 20, 2011.


Editor’s Note: Peter Budnick is a Senior Editor for Ergonomics in Design.

This article originally appeared in The Ergonomics Report™ on 2011-04-20.