Seasonal variations in socially and legally unacceptable sexual behaviour

The calendar dates, over the 15-year span 1966-1980, of committed rapes by eight male recidivists and offences of sexually indecent or immoral behaviour by eight other male recidivists were gathered from the files of the Préfecture de Police, Paris, France. Each offender of the first group had committed from two to six rapes, while each offender of the second had committed from two to 16 incidences of indecent behaviour. Although the reported rapes took place during several calendar years, almost all, 18 out of 22 offences, were committed by the eight rape-recidivists during the 4-month span of July-October. Single cosinor analysis of these data revealed a circannual rhythmicity (P less than 0.03) with luminal diameter being 10 August +/- 34 days (the 95% CL). The peak time of indecent sexual behaviour, exclusive of rape, against females occurred during September with secondary peaks in February and June; such offences directed against males peaked in October. 'Bootstrap' and 'Jackknife' methods confirmed seasonality within all data sets, except for the offences of indecent behaviour.