Severity of penalty, seriousness of the charge, and mock jurors' verdicts.

It has been suggested that jurors in criminal trials are less likely to convict when the penalty is more severe or the charge is more serious. This was explained by Kerr (1975) in terms of a perceived increase in the cost of a Type I error (convicting an innocent person) that resulted in a criterion shift in the amount of evidence jurors required to vote guilty. The previous research found only weak support for the prediction regarding severity but consistent support for the predicted effect of seriousness. However, in the case materials used in these studies, more evidence was legally required to prove guilt on the more serious charges. This article presents studies in which the amount of evidence needed to prove guilt was equated for all charges. Under these circumstances, there was no effect on verdicts of seriousness of charge or severity of penalty and no evidence of a criterion shift due to either variable. There may still be reason to believe that these factors affect real juries, but this belief is not supported by the systematic evidence from mock jury studies.