Akademik Veri Yönetim Sistemi
VIRTUAL IACFT TURKISH SPEAKERS’ DAY 2022, Kütahya, Türkiye, 31 Mart - 01 Nisan 2022, ss.54, (Özet Bildiri)
POSSIBILITY OF RELATING SOMEONE WITH A CRIME BY SECONDARY DNA TRANSFER
Yasemin Soysal1,2, Erdem Özkara1
1Dokuz Eylül University, Faculty of Medicine, Department of Forensic Medicine, İzmir
2Dokuz Eylül University Institute of Health Sciences, Department of Molecular Medicine, İzmir
Introduction: DNA on a material can be present on a surface by primary transfer of direct contact or indirect transfer without any contact. If DNA comes on an item via a second individual transfer it is called secondary transfer. Tertiary transfer is also possible if there are two intermediary steps. DNA can be transferred to crime scene by active or passive way. DNA profile which is detected on a touched object at the crime scene might have been unrelated with the crime itself. Dangers has to be considered about the risks of alternative (innocent) transfer and this situation gets attention of forensic professionals and studies have been designed to investigate the importance of secondary transfer.
Casework: Several studies conducted, in one study, Oorschot tested the potential for secondary transmission by taking a swab from the hands of the participants before and after a one-minute handshake. One of the four hands tested revealed the transfer of DNA from one person to another. This finding led the authors to conclude that secondary DNA transfer is a real possibility and may complicate the interpretation of forensic DNA evidence. In 2002, Lowe et al., in their study using more sensitive kits and methods, detected the complete DNA profile in an object that a person had never touched. In 2010, Goray demonstrated the secondary DNA transfer from biological materials by specifying the kit and method they used.
Cale et al. evaluated whether this increased sensitivity with more sensitive technological opportunities could lead to the detection of interpretable secondary DNA transfer profiles. In the study, 12 flat plastic handle knives and 12 recessed plastic handle knives were used. After two minutes of hand-to-hand contact (handshake), the participants immediately picked up the designated knives and held them for two minutes. Samples were swabbed from the blades, DNA was obtained and analyzed. When the samples were examined to determine whether the obtained DNA profile was from a single participant or more than one participant and whether there were other foreign DNA sources, it was observed that the DNA of secondary people who did not directly touch the knife was detected.
Results: Secondary DNA transfer is a concern for forensic DNA analysts because it may falsely associate someone with a crime; insert foreign DNA into a forensic sample, and may lead analysts and other forensic experts to the wrong conclusion that DNA left on an object is the result of direct contact. If the DNA found at the crime scene is not examined well, it may not lead us to find the real criminal and create a new victim.
Keywords: Secondary DNA transfer, DNA contamination, Crime scene investigation, Touch DNA, DNA analysis