Bus and Motor Coach Library

Using Expert Testimony to Assist Jurors

Author - Tom Frenkel (2003)

Legal disputes often involve experts who offer their opinions in specific areas of expertise.  Expert testimony is presented to assist a jury’s understanding of topics which are not generally common knowledge.  Trial attorneys seek experts whose opinions will carry great weight, in order to influence the jury.  In most jurisdictions a person may be deemed an “expert” by a mere showing that he or she has more knowledge than the average person, in the area which is the subject of expert testimony. 

A jury will typically be informed of a testifying expert’s education, knowledge, skills, experiences, publications and achievements.  Experts in human behavior and condition are commonly used.  As society advances in science, technology, and engineering, specialized experts are increasingly used.  Experts are also commonly called upon to offer opinions which are based upon the factual circumstances which are established in a dispute. Let’s look at a few examples where experts may be utilized in transportation litigation, one for human and behavioral testimony and a couple examples of technological testimony.

Driver fatigue is commonly investigated whenever a collision, crash, or other alleged wrongful incident occurs.  Professional drivers are all aware of the regulations which dictate duty hours, but duty hour compliance is not the sole determining factor as to whether the driver was fatigued.  The human body is subject to daily cycles of activity, sleep, digestion, etc.  These cycles fall under the rubric of circadian rhythms.  You might recall studies which were published years ago (some decades ago) which involved persons who were living in isolated chambers where there was no natural light, nor were there clocks or calendars provided.  Basically, all external references to time were removed, in efforts to determine the test subjects’ natural activity/sleep schedule, as opposed to the traditional day/night schedule.  These were studies in circadian rhythms.

When a driver’s schedule changes, driver fatigue is always suspect.  Allegations of driver fatigue go far beyond “falling asleep at the wheel.”  Expert testimony would be sought to support, or to counter, allegations of driver distraction, irritability, road rage, impaired perception, risk-taking behavior, slower reaction times (as in braking or steering), and a host of other side-effects of fatigue.  A driver can be shown to be fatigued, even when the driver is in perfect compliance with duty hour regulations.  Of course, the jury will be asked to consider the driver’s duty hour compliance, as well.

Advanced technology is commonly the subject of expert testimony.  For instance, the average modern motor vehicle has sophisticated engine monitoring computers.  Most commercial operators I speak with consider those systems in terms of maintenance and fuel efficiency.  Those computers monitor RPMs, control transmission shift-points, control fuel to air ratios, control operating temperatures, etc.  In a courtroom, however, experts will commonly use the reports from these black boxes to testify about vehicle speed, the use of cruise controls, braking and other matters of driver conduct.

Not long ago I was involved in a case where engine monitor data from a tractor-trailer was examined by an expert who interpreted the data to mean that the vehicle was operating under cruise control, at a speed higher than the posted limit, without braking when it impacted a backhoe which was being operated by a road crew worker. 

I recently attended a seminar of the Transportation Lawyers Association where such an expert displayed an analysis of black box data from a case where he’d testified that a cruise control was in use at the time of impact in a collision.  He displayed graphs showing that the accelerator response to minuscule speed variations was continuous and immediate.  There were accelerator control changes which would have been imperceptible to humans, and the reaction to speed variations were faster and more exacting than a driver could accomplish.  The immediate and dramatic “overspeed” of the engine, when vehicle speed diminished, was conclusive that the cruise control was engaged at the time of impact.  Incidentally, these technologies are not limited to commercial vehicles.  Odds are that your family auto has information which is just as sophisticated, and available.

Another type of technology which is growing in use involves position monitoring and reporting, such as through Global Positioning System (GPS) geo-synchronous satellite data.  Experts would testify as to the reliability of such systems to establish the location of a vehicle at a given time.  I’ve heard drivers resist the use of such systems by their employers.  There is concern that “big brother” is always watching.  I think it’s noteworthy that most of the same drivers carry cell phones which continually communicate to the local cellular-service towers, whenever they are turned on.  In fact, current manufacture cell phones which are sold in the U.S. all have GPS reporting capability, to establish the caller’s location in the event of a 911 report.  Criminal investigators frequently use cellular data to establish the locations of “all the usual suspects” when serious crimes are committed.  When a civil action or a criminal prosecution involves such information, experts are hired to explain the information and offer their interpretations to the jury.

We live in a society which scrutinizes and analyzes data in more depth than ever before.  When those analyses involve the courts, they are designed to get at the objective truth.  Juries rely on experts in data collection and interpretation to arrive at just verdicts.  On a practical note, we’re all best advised to use common sense to avoid lawsuits and the use of experts.  For instance, the best ways to avoid questions about fatigue, vehicle operation, and location are to avoid damage and injury.  A well-rested, diligent, and careful driver has far less exposure to lawsuits.

Thomas R. Frenkel is an attorney, licensed to practice in Illinois, Minnesota, and the District of Columbia.  Mr. Frenkel has a unique blend of legal and practical transportation and hospitality industry experience.  He is a past president of the National Tour Association (NTA), a past two-term board member of the Travel Industry Association of America (TIA), a founding member of the Hospitality Skills Standards Board (which was created under directive of the United States Department of Labor), and a member of the Transportation Lawyers Association.  Tom Frenkel was the Editor in Chief of the Southern Illinois University Law Journal.  He practices law from his office at Feirich/Mager/Green/Ryan, Attorneys at Law, a law firm which enjoys the highest ratings in both quality of legal service and quality of ethical standards by Martindale-Hubbell, an independent service which rates legal professionals.  Tom Frenkel may be contacted at FMGR, 2001 West Main Street, P.O. Box 1570, Carbondale, Illinois, USA, 62903-1570.  Phone: (618) 529-3000, email:  This magazine is proud to feature Mr. Frenkel's commentary, as a contributing writer.  This column is featured for the interest of our readers, but does not constitute legal advice; nor does any attorney-client relationship arise through its publication.