Time since death is extremely important topic of study in Forensic medicine. Time of death is a question almost invariably asked by investigating authorities to link the criminals with the crimes. Determining the time since death has always been a topic of keen interest amongst the forensic pathologists from its inception till date. Many workers in forensic medicine have tried to investigate to determine the time of death on the basis of post mortem findings. From the ancient era, the triad: Algor mortis, Rigor mortis and Liver mortis has been the basis for ascertaining the time since death collectively. Till date it is still the important and most fascinating criteria to ascertain the time since death. This assessment covers the importance of the time since death from rigor mortis in forensic science.