Estimation of time since death is one of the challenges in forensic science. Autolysis triggers decomposition, which induces cellular destructive changes causing cell death. Aim: This work aimed to study mRNA expression based on the process of cell death signaling, to evaluate changes in oxidant/ antioxidant parameters and immunohistochemical postmortem changes in the rat's liver. Methodology: 35 rats were divided into 5 groups. The liver was extracted at (0, 3, 6, 12, 24) hours postmortem, to measure the mRNA expression of (FasL) and (PTEN) by quantitative PCR in addition to MDA, CAT, GPx, and immunohistochemical postmortem changes. Results: MDA began to rise noticeably after death, CAT began to decline at 3 hours, GPx declined at 6 hours. The relative expression of FasL gene in the rat's liver increased at 3, 6, 12, and 24 h. However, at 24 h pm, it suddenly decreased. Also, the relative expression of the PTEN gene is increased from 3 to 12 h and then decreased at 24 h postmortem. Regarding mRNA levels of caspase-3 and Bax, there was a time-dependent rise till 12 h and a noticeable decline at 24 h. Oppositely the relative expression of the Bcl2 gene decreased from 3 to 24 h postmortem. The relative mRNA expression of FasL, PTEN, caspase 3, and Bax showed a strong positive correlation with the early postmortem time. The relative expression of the Bcl2 gene was found to correlate negatively with the early postmortem time. Conclusion: These findings supported our preliminary theory, since FasL, PTEN, caspase 3, Bax, and Bcl2 are involved in necrobiosis signaling mechanisms. They are potential candidates to analyze the time since death in 24h or less intervals. The oxidant/antioxidant and immunohistochemical changes in the liver of rats are also important to determine the time after death. It is possible to estimate the early postmortem interval using these biochemical markers.