Determination of postmortem time interval holds significance in defining the direction of a forensic investigation. The conventional methods of estimating PMI explore the early postmortem changes appear in the body including rigor mortis, livor mortis, and algor mortis. Though such techniques are widely used in PMI estimation, such methods are relatively inaccurate and offer limited practical relevance. Many biochemical and molecular techniques have been explored using the postmortem blood samples for the accurate, reliable estimation of PMI. Besides the analysis of metabolites and proteins, molecular techniques measuring the level of DNA and RNA in the postmortem blood has shown a huge potential in estimating PMI. The descendent trend of the amount of DNA postmortem has shown its correlation with the PMI. The degradation pattern of DNA can be studied by using flow cytometer, image analysis techniques, single cell gel electrophoresis (SCGE), DNA amplification assay, and other assays such as the terminal deoxynucleotidyl transferase assay. Similarly, RT-PCR-based analysis of expression pattern of mRNA, miRNA, and circRNA can also provide crucial information on the PMI. mRNA of Actb, Gapdh, Ppia, Srp72, β-actin, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) have shown potential use in PMI estimation.