A study examined the effect of attitude toward capital punishment on the evaluation of evidence and the determination of guilt. Subjects were 224 undergraduate students who read a description of a murder. They then received two, four, or six items of evidence relevant to the defendant's guilt. Subjects were asked to determine a verdict and indicate their certainty of that verdict, whether they were for or against capital punishment, and how certain they were of the correctness of that stance. The results supported the hypotheses that (1) persons favoring capital punishment would be significantly more certain of their attitude than those opposed to it, (2) those who found the defendant guilty would be significantly more certain of their verdict than would those who found the defendant not guilty, (3) those who received more evidence of guilt would be significantly more certain of their verdict than those receiving less evidence, and (4) given the same amount of evidence, more people favoring capital punishment would find a guilty verdict than those opposing it. The results did not support the hypothesis that people favoring capital punishment would be more certain of their verdict than would those opposing it. In light of the "death qualified" juries required by some states for capital crimes, it is significant that persons favoring capital punishment are different from those who oppose capital punishment both in the certainty with which they find their verdict and in the amount of evidence they require to find a defendant guilty. (HTH)