12 real forensic cases solved by the DNA STR-typing of skeletal remains exposed to extreme environment conditions, without the conventional bone pulverization step.

Abstract

DNA identification of human skeletal remains play a valuable role in the forensic field, especially in missing persons and mass disasters investigation. Hard tissues, such as bones and teeth, represent a very common kind of samples analyzed in forensic laboratories because often they are the only biological materials remaining. However, the major limitation in using these compact samples rely on time consuming and labor-intensive treatment of grinding them into powder before proceeding with the conventional DNA purification and extraction step. In this context, a novel DNA extraction assay, called the TBone Ex kit (DNA Chip Research Inc.), was developed to digests bone chips without powdering "as reported by Kitayama (JAMA 12:84-89, 2010)." Here, we simultaneously analyzed bone and tooth samples obtained by our police laboratory that belonged to 15 different forensic cases from Sardinia (Italy). The total of 27 samples were recovered from different scenarios and were exposed to extreme environmental factors, including sunlight, seawater, soil, fauna, vegetation and high temperature and humidity. The TBone Ex kit was used prior to the EZ2 DNA extraction kit on the EZ2 Connect Fx instrument (Qiagen), and high quality autosomal and Y-chromosome STRs profiles were obtained for the 80% of the cases, in a relatively short time frame. This study provides additional support for the use of the TBone Ex kit for digesting bone fragments/whole teeth as an effective alternative to pulverization protocols. We empirically demonstrated the effectiveness of the kit in processing multiple bone samples simultaneously, largely simplifying the DNA extraction procedure, and the good yield of recovered DNA for downstream genetic typing in highly compromised forensic real specimens. In conclusion, the results of this study appear useful for forensic laboratories, to which the various actors of the criminal justice system - such as potential jury members, judges, defense attorneys and prosecutors - require immediate feedback.