The studies sought to determine the accuracy of jurors in detecting deception; the effects of variations in the mode of presentation of a trial, e.g., televised or transcripts, on jurors' ability to detect deception; and what sources of information facilitate a juror's ability to distinguish between deceitful and truthful testimony. The first study used Ekman and Friesen's deception-inducing techniques while altering the questions asked of college student interviewees and using videotapes in a fashion similar to the courtroom. The second study extended the scope of the first study, employing procedures that permitted introduction of a live condition. Results suggested that attributions of truthfulness and deceitfulness, which jurors must frequently make to weigh testimony and reach decisions, may be of questionable validity. In general, jurors probably have difficulty assessing veracity of witnesses. Delegating to a jury the responsibility of weighing witness credibility should be approached cautiously. Concerning the use of videotaped materials in courtroom trials, findings indicate that the effects on judgmental accuracy of a juror's presence during testimony -- that is, seeing and hearing it live as opposed to observing the testimony on videotape, are insignificant. Individuals are not very accurate in detecting deception regardless of whether they observe the source live or on videotape. Similarly, judgments of witness veracity are not influenced by the use of color as opposed to black-and-white equipment. Findings support the generalization that observers who attempt to detect deception by strangers can do so with little more than chance accuracy. Eight footnotes, 10 tables, and 32 references are included.