Serial homicide offenders and the lunar cycle

The purpose of this research is to establish whether there are factors that contribute to the predatory activation of serial homicide offenders (SHOs) in relation to the lunar cycles. In order to move the discussion away from the media fascination with SHOs and the perpetuation of myths regarding the lunar cycle, we used a quasi-Poisson log-linear regression model based on 9976 homicides that occurred between 1 January 1960 and 30 November 2016. The results indicate that lunar phase does not influence the frequency of homicides (p = 0.997), with rate ratios across Moon phases ranging narrowly around 1.00 (e.g., full moon RR = 1.03; 95% CI: 0.66-1.63). Likewise, other variables related to the lunar cycle, such as the Moon´s distance from Earth, seasonal variation, and the percentage of the Moon´s illuminated surface, were not statistically significant predictors of homicide. In contrast, the age of the victims showed a strong and significant relationship, with persons aged 15-64 being 8.71 times more likely to be homicide victims than others (p < 2e-16). In general, these findings, obtained over a 56-year observation period, provide no statistical evidence of a relationship between the lunar cycle and SHO criminal activity. The large sample size and extended temporal coverage enhance the generalizability of these conclusions.