Email Print Share

News Release 95-71

NSF Study Yields Insights into Impact of Expert Testimony

October 12, 1995

This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date; please see current contact information at media contacts.

Jurors' perceptions of expert testimony depend heavily on whether the expert is paid or highly credentialed -- or both according to NSF-funded research on the effects of science and technology testimony in the legal system. The effect of these factors is magnified when the testimony is complex.

"The U.S. legal system in this age of technology increasingly depends on testimony by science and technology experts, particularly in civil litigation," said legal scholar Joan Hall, a member of the research team. "That raises some important questions, such as whether peripheral factors influence jurors more than facts and testimony."

Princeton University psychologist Joel Cooper led the research project which combined focus groups and experiments to determine the effects of expert science and technology testimony in the legal system. The research specifically targeted product liability cases.

Among the studies' most interesting findings:

  • When testimony was given in complex language, jurors were more likely to form judgments based on the credentials of the expert rather than the validity of the testimony.
  • Experts who are paid highly, and who jurors assumed testified frequently, were considered hired guns and were regarded less favorably, regardless of their testimony.
  • In medical liability cases, jurors' decisions were affected by their own or others' past medical experiences and by whether the defendant was an individual or a corporation.
  • A court appointed expert did not automatically convince or influence jurors more than experts called by the defense or prosecution.

According to Hall, the most effective expert witness was one with strong credentials who used simple language. However, the addition of pay complicated the findings. An expert who was paid very highly and had strong credentials was not always an effective witness, from the jurors' point of view. "Perhaps jurors feel that the highly paid and high- credentialed expert is using his position to make money," said Hall.

Expert witnesses are used in 86 percent of civil cases, with an average of four experts in every trial, according to the study. "In an effort to validate the claims that are in dispute, a rising number of expert witnesses are being used in any given case, and sometimes they contradict each other," Hall pointed out. "How is a juror to determine which expert is correct, when each claims to have the answer and the juror is unfamiliar with the issue?"

Based on this research at least, jurors use peripheral factors, in addition to the testimony itself, to make their judgments.

According to William P. Butz, NSF's division director for social, behavioral and economic research, the findings have implications for new technologies in this country. "U.S. industry may be less likely to develop or market major innovations, because of the risk that they will not be able to convince juries with expert testimony," he said.


Media Contacts
Mary E. Hanson, NSF, (703) 292-8070, email:

Program Contacts
Len Lederman, NSF, (703) 306-1742, email:

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2018, its budget is $7.8 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives more than 50,000 competitive proposals for funding and makes about 12,000 new funding awards.

mail icon Get News Updates by Email 

Useful NSF Web Sites:
NSF Home Page:
NSF News:
For the News Media:
Science and Engineering Statistics:
Awards Searches: