Abstract : One of the important forensic pathology aspects is the establishment of the time since a death has occurred i.e. post-mortem interval (PMI). It gives the police a start to their investigation and help in dealing more professionally with the evidence available. The objective of the present was just to measure the yield of total RNA and cDNA at different post mortem intervals using most RNA extraction techniques in the heart tissue of Wister rats. A total of 36 female Wister rats (250–300 g, aged 12 weeks) were included in this study, with the exclusion of male rats. The standard and recommended laboratory conditions were provided to the animals. The autopsy of heart tissue was taken at 0, 16, 24, 30, 42 and 48 hours’ time. Total RNA yield was measured by Nanodrop and cDNA through real-time PCR. From the findings of the present study, we can conclude that post mortem heart tissue gives an acceptable yield of RNA and cDNA for further downstream applications