In the lay judge system, which started in 2009, great variability has been observed among judgments of prison terms compared to the previous judge system. As one of the causes, this study focused on lay judges’ use of heuristics and four experiments were conducted to examine the role of heuristics in judicial judgment. The results suggested that anchoring and adjustment heuristics are used in the determination of the appropriate punishment. Even those that are apparently unrelated, reference points (anchor) that are presented in advance, had an impact on decisions about the length of prison terms.