The mock jurors, 128 university students, watched 2 eyewitness videotapes relating to the robbery of a convenience store and murder of a store clerk. One eyewitness was hesitant and vacillating in his testimony, while the other was confident of his identification and answered all questions in a straightforward manner. The same male portrayed both witnesses. Subjects subsequently watched tapes of a psychologist giving general and very detailed expert testimony and completed an 11-item questionnaire. The results showed that jurors continued to use eyewitness confidence as a guide to assessing eyewitness accuracy after viewing expert psychological testimony. Expert testimony reduced belief in the eyewitness more in the low-confidence than in the high-confidence condition. Expert testimony influenced jurors' specific beliefs concerning the case at hand, as well as the subjects' general beliefs concerning the accuracy of eyewitnesses. The study also found significant differences between the effects of general and specific expert testimony. Tables and approximately 40 references. (Author abstract modified)