Testing the Comprehensibility of Jury Instructions: California's Old and New Instructions on Circumstantial Evidence

Abstract

In 2003 and 2005 the Judicial Council of California approved new pattern civil and criminal jury instructions. This article reports on research comparing comprehension of the new civil instruction on circumstantial evidence with comprehension of the old circumstantial evidence instruction. The authors, one of whom was a member of California's Task Forces on Jury Instructions, conducted a study in which research participants were given either the new or old instruction and then asked to state whether each of 16 different scenarios described direct or circumstantial evidence. The authors conclude that the new instruction is more effective than the old one at overcoming the common understanding of "circumstantial evidence" as "weak evidence." The traditional instruction was unable to overcome prior (incorrect) knowledge, whereas the new one, which contained examples, was relatively more effective in this regard. Because even participants with the new instructions had difficulties with the concept, the authors argue that successful instructions on circumstantial evidence would emphasize the importance of strong as compared to weak evidence rather than attempting to educate jurors about the distinction between direct and circumstantial evidence.