Investigation into DNA recovered from human teeth for forensic applications

• Main Author: Haikney, Tarryn
• Other Authors: Heathfield, Laura
• Format: Dissertation
• Language: English
• Published: Faculty of Health Sciences 2020
• Subjects: Forensic Medicine and Toxicology
• Online Access: http://hdl.handle.net/11427/32223

In South Africa, there is a burden of unidentified deceased individuals in forensic mortuaries. When human remains are severely compromised, hard tissues may provide the only DNA source for identification. The QIAamp® DNA Investigator Kit is used in forensic laboratories worldwide, including in South Africa, to extract DNA for identification purposes. However, in local forensic casework, the DNA recovered from teeth is often of insufficient quantity and quality for generating a DNA profile. The phenol-chloroform DNA extraction method has demonstrated improved, yet inconsistent results, when used on hard tissues. Therefore, this study assessed DNA recovery from 52 human control teeth from three deceased individuals, using an optimised phenol-chloroform method. This method involved an overnight demineralisation, two additions of phenol/chloroform/isoamyl alcohol (25:24:1) and an ethanol precipitation, as used by the Australian Federal Police. Quantitative PCR (Quantifiler™ Trio DNA Quantification Kit) and DNA profiling (PowerPlex® ESI 16 System) were then used to assess DNA quantity and quality. Results were compared to those obtained from the same teeth but extracted using the QIAamp® DNA Investigator Kit. The phenol-chloroform method recovered DNA with significantly higher yields (p = 0.0454) and significantly less degradation (p < 0.0001). Despite this improvement, there was no significant difference in DNA profiling success. This study also did a preliminary analysis of other factors affecting results and suggested that premolars might be the best tooth type with regards to DNA quantity, quality and profiling. Furthermore, dental disease and jawbone had a significant impact on results from teeth. Lastly, the phenol-chloroform method was applied to six teeth from a marine decomposition case to assess its performance in a local forensic setting. DNA metrics were particularly poor in this casework example, highlighting how different forensic and control environments are and the need for further optimisation. Overall, this study supports the use of the phenol-chloroform method and has provided a preliminary suggestion of the best tooth type, jawbone and tooth condition for DNA analysis for forensic human identification.