Estimation of postmortem interval is very important in forensic medicine. It aids to know the clue of the crime , aids the the police in their work and to find the suspected assailant. There are multiple methods that are used for this purpose, there are the classical method as algor mortis, hypostasis ,rigor mortis and putrefaction. Great advances has occured in biochemical changes that occur after death as multiple markers had been found to correlate with the time passed after death . DNA and RNA has agreat role in this field helping in estimating the time passed since death by different changes that occure after death