Many biological evidences that submitted to forensic laboratories are not convenient for DNA analysis. Because of they are not collected and packaged correctly and not stored in the appropriate environment. For this reason, DNA test and many other non-DNA tests cannot be performed . In order to protect blood evidence, should be known the reason of the deterioration. For this intention, we investigated the kind of microorganisms which decay the evidences, the effect of temperature, effect of package types and resistance of biological evidence to putrefaction. We aimed to determine the best condition for evidence safety. In our study, evidence modules were prepared using five different grounds, three different temperatures, two different time durations and three different package types. After the waiting periods, packages were opened and microbiological analyzed. At the end of microbiological analyzes, it determined that, as the waiting time of packages increases, microbial reproduction increases. The most decaying was seen on blood drips on the wall. After wall, respectively wood, sponge, fabric and knife are decaying by microorganism. The most putrefaction is seen at 40C, the least putrefaction is seen in the room conditions. Paper envelopes and cloth bags have been found to be better for protecting evidences. However, evidences that were completely dry were found to be better preserved in nylon bags.
Key words: Evidence, microorganism, blood, putrefaction, crime scene