Post-mortem interval (PMI) is a major component of investigation in forensic science. It is one of the fundamental tasks for forensic pathologist when a body is found. According to criminal law point of view, a correct estimation of the PMI allows authentication of witness statements, thus restrict the number of suspects. Accurate PMI estimation is difficult because of intrinsic and extrinsic factors. Analysis of the biochemical changes in glucose and electrolytes for PMI estimation has made significant progress. Molecular ways in which measurable or quantifiable technique for degradation of nucleic acid molecule such as DNA and RNA, may be the good indicator for PMI. Several studies have tried to determine changes in molecular markers to provide more useful information for PMI. The studies demonstrated mixed results that showed the influence of ante and post-mortem factors on nucleic acid degradation. More studies would be required in order to standardize on human cases under standard parameters. Thus, molecular aspects of forensic involves this application of omicsin medical sciences to investigate cause of death and its process at the genetic basis and biological molecular level.