In forensic medicine, there is an undefined data background for the phenomenon of re-establishment of rigor mortis after mechanical loosening, a method used in establishing time since death in forensic casework that is thought to occur up to 8 h post-mortem. Nevertheless, the method is widely described in textbooks on forensic medicine. We examined 314 joints (elbow and knee) of 79 deceased at defined time points up to 21 h post-mortem (hpm). Data were analysed using a random intercept model. Here, we show that re-establishment occurred in 38.5% of joints at 7.5 to 19 hpm. Therefore, the maximum time span for the re-establishment of rigor mortis appears to be 2.5-fold longer than thought so far. These findings have major impact on the estimation of time since death in forensic casework.