Source Credibility and the Language of Expert Testimony1

In an examination of the language used by expert witnesses during actual courtroom testimony, it was expected that experts who exhibited content themes related to their credentials or experience (expertise) and to objectivity (trustworthiness) would be perceived as being more credible. Forty‐three segments of expert testimony were taken from actual court transcripts and content analyzed. Two‐factor analytically derived factors predicted expert witness membership into low‐ and high‐credibility groups, defined a priori by credibility judgments of undergraduate raters (n = 348). These factors were (a) the use of passive voice and (b) the witnesses' background and qualifications. Further analyses revealed that perceptions of expert witness credibility were also a function of the usage of words that connote power (an expert's official status, degree of prominence and/or recognition) or negative (suffering or damage). Results are discussed in terms of dimensions of source credibility and their parallels to past research in persuasion.