This study just appeared in the journal Psychological Science:
The degree of punishment assigned to criminals is of pivotal importance for the maintenance of social order and cooperation. Nonetheless, the amount of punishment assigned to transgressors can be affected by factors other than the content of the transgressions. We propose that sleep deprivation in judges increases the severity of their sentences. We took advantage of the natural quasi-manipulation of sleep deprivation during the shift to daylight saving time in the spring and analyzed archival data from judicial punishment handed out in the U.S. federal courts. The results supported our hypothesis: Judges doled out longer sentences when they were sleep deprived.
The Monday after the shift to day light savings time is associated with about 40 minutes of lost sleep. Other studies have found an increased number of car accidents on that day. The authors of this study report that sentences are 5% longer than those on comparison Mondays.
An interesting result, although I do have some skepticism about how well confounding variables can be controlled statistically.