Reliability and Reproducibility of DNA Profiling from Degraded Samples in Forensic Genetics

Forensic DNA analysis is widely used to determine kinship and the identity of evidence from the crime scene and it is especially important in the identification of human remains after different types of exposure (water, heat, etc.). Currently, there are no official recommendations for forensic scientists as to which bones and tissues are the most reliable among degraded DNA samples. Since 2014 more than 350 fragments of unidentified corpses have been examined in the Forensic Biological Department (Republic Bureau of Forensic Medicine, Kazan, Russia). Based on our experience, the most reliable and reproducible DNA profiles are obtained from lower limber bones (in 90% cases), muscles (in 85% cases) and ribs (in 80% cases). However, we discovered a new source of DNA – the odontoid process of the 2nd cervical vertebra, which contains a high amount of DNA with a better state of preservation than many other bones. According to our results, when a complete skeleton or unidentified corpse is found, it is advisable to provide bones with soft tissue remnants in the absence of deeply embedded putrefactive changes. When working at the crime scene, special attention should be paid to separating small bones and fragments from skeletal remains