In many criminal investigations, valuable information regarding the physical appearance of suspected perpetrators or the time and order of events that transpired are provided by eyewitness accounts. However, the information obtained from eyewitnesses is often constrained by human recollection or subjective accounts and provides a biased description of the perpetrator's appearance or an inaccurate time line of events. Additionally, in numerous situations eyewitness accounts may not be available. An increasing reliance therefore is placed on the biological evidence recovered during criminal investigations to act as a silent witness, providing unbiased and scientific information that may aid in the resolution of criminal investigations. While the current capabilities of operational forensic crime laboratories include analytical methods to allow for a determination of the origin of a biological stain and for the recovery of a genetic profile of the donor, the sensitivity of such methods is not always sufficient to accommodate the limited amounts of biological material often recovered in forensic casework, Therefore, it is critical that continual advancements in the analysis of low template samples be made. In this report, we have sought to identify novel protein, RNA and DNA biomarkers that, in combination with enhanced profiling strategies, would allow for a determination of the time since deposition, the body fluid of origin and the genetic profile of the donor ("genetic eyewitness") of forensic low template specimens. First, we have developed a novel strategy for the determination of the time since deposition of dried bloodstains using spectrophotometric analysis of hemoglobin. An examination of the Soret band (λmax = 414nm) in aged bloodstains has revealed a previously unidentified hypsochromic shift as the age of the stain increases. The extent of this shift permits a distinction to be made between stains that differ in age by only minutes, hours, days and months thus providing the highest resolution of any previously developed method. We also demonstrate that it may be possible to utilize a decline in enzyme activity to determine the age of a forensic biological stain. Second, we demonstrate that the differential expression of a panel of nine miRNAs allows for the identification of the body fluid origin of forensic biological stains using as little as 50pg of total RNA. This is the highest reported sensitivity of any RNA-based approach and this assay has demonstrated a high degree of specificity for each body fluid tested. The final task of this work was to identify novel DNA biomarkers and to develop enhanced profiling strategies to allow for greater sensitivity and reliability in the genetic profiling of low template samples. We demonstrate that the use of laser capture micro-dissection and enhanced amplification strategies resulted in the ability to obtain genetic profiles from as few as 2-5 epithelial cells and 5-10 sperm cells with greater reproducibility than previously reported studies. The use of a novel whole genome amplification method provided the ability to not only increase the quantity of genetic material obtained from micro-dissected cells but also the ability to recover additional genetic information from individual samples using novel DNA biomarkers. The novel biomarkers and profiling strategies described in this report provide the basis for the establishment of a molecular "genetic eyewitness" from low template forensic samples and demonstrate the future potential for routine and reliable analysis of trace amounts of genetic material recovered from low template biological evidence.
Doctor of Philosophy (Ph.D.)
College of Medicine
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Hanson, Erin, "The Development of a "Genetic Eyewitness" Profiling System For Low Template Forensic Specimens: Identification of Novel Protein, RNA, and DNA Biomarkers" (2008). Electronic Theses and Dissertations. 6146.