Keith L. Monson

Characterization of the Caucasian Haplogroups Present in the SWGDAM Forensic mtDNA Dataset for 1771 Human Control Region Sequences

Currently, the Scientific Working Group on DNA Analysis Methods (SWGDAM) mtDNA dataset is used to infer the relative rarity of mtDNA profiles (i.e., haplotypes) obtained from evidence samples and for identification of missing persons. The Caucasian haplogroup patterns in this forensic dataset have been characterized using phylogenetic methods. The assessment reveals that the dataset is relevant and representative of U.S. and European Caucasians. The comparisons carried out were both the observation of variable sites within the control region (CR) and the selection of a subset of these sites, which partition the variation within human mtDNA control region sequences into clusters (i.e., haplogroups). The aligned sequence matrix was analyzed to determine both single nucleotide polymorphisms (SNPs) in a phylogenetic context, as well as to check and standardize haplogroup designations with a focus on determining the characters that define these groups. To evaluate the dataset for forensic utility, the haplogroup identifications and frequencies were compared with those reported from other published studies.

Accuracy of standard craniometric measurements using multiple data formats

UNLABELLED With continuing advancements in biomedical imaging technologies, anthropologists are increasingly making use of data derived from indirect measurement and analysis of skeletal material. To that end, the purpose of this study was to test the reliability of 26 standard craniometric measurements routinely utilized in forensic casework across several different imaging technologies. Measurements from five crania of known individuals were collected in duplicate by two anthropologists via computed tomography (CT) scans and three-dimensional (3D) laser scans of the known skulls. The laser scans were also used to create prototype models of the known skulls. These prototypes were, themselves, laser-scanned, and measurements were also collected from the prototypes and the laser scans of the prototypes. Measurement sets from each technology were then compared with one another using the previously collected osteometric measurements taken on the crania themselves as the ground truth. RESULT indicate that, while the majority of measurements showed no significant differences across data formats, a handful were found to be problematic for particular technologies. For instance, measurements taken in a supero-inferior direction (e.g., BBH, OBH) from CT scans were prone to greater deviation from direct measurements of the cranium than other technologies, especially for CT scans taken at 5 mm thickness and increment. Also, several measurements defined by Type 1 landmarks, particularly those occurring at complicated or indistinct suture junctures (e.g., ASB, ZMB), were found to have high variance across all technologies while measurements based on Type 3 landmarks proved to be highly reproducible. This is contrary to measurements taken directly on crania, in which measures defined by Type 1 landmarks are typically the most reliable, likely attributable to diminished or totally obscured suture definition in the scan data. If medical imaging data are to be increasingly utilized in anthropological studies, it may be prudent to bear in mind that the reliability of measurements taken on an actual skull may not be the same as for measurements taken from medical scans.

Assessment of presentation methods for ReFace computerized facial approximations.

Facial approximations (whether clay sculptures, sketches, or computer-generated) can be presented to the public in a variety of layouts, but there are currently no clear indicators as to what style of presentation is most effective at eliciting recognition. The primary purpose of this study is to determine which of five presentation methods produces the most favorable recognition results. A secondary goal of the research is to evaluate a new method for assessing the accuracy of facial approximations. Previous studies have evaluated facial approximation effectiveness using standards similar to studies of eyewitness identification in which a single, definitive choice must be made by the research participant. These criteria seem inappropriate given that facial approximation is strictly an investigative tool to help narrow the search for potential matching candidates in the process of identification. Results from the study showed a higher performance for methods utilizing more than one image of the approximation, but which specific method performed best varied among approximation subjects. Also, results for all five presentation methods showed that, when given the opportunity to select more than one approximation, participants were consistently better at identifying the correct approximation as one of a few possible matches to the missing person than they were at singling out the correct approximation. This suggests that facial approximations have perhaps been undervalued as investigative tools in previous research.

Initial progress in the recording of crime scene simulations using 3D laser structured light imagery techniques for law enforcement and forensic applications

Representation of crime scenes as virtual reality 3D computer displays promises to become a useful and important tool for law enforcement evaluation and analysis, forensic identification and pathological study and archival presentation during court proceedings. Use of these methods for assessment of evidentiary materials demands complete accuracy of reproduction of the original scene, both in data collection and in its eventual virtual reality representation. The recording of spatially accurate information as soon as possible after first arrival of law enforcement personnel is advantageous for unstable or hazardous crime scenes and reduces the possibility that either inadvertent measurement error or deliberate falsification may occur or be alleged concerning processing of a scene. Detailed measurements and multimedia archiving of critical surface topographical details in a calibrated, uniform, consistent and standardized quantitative 3D coordinate method are needed. These methods would afford professional personnel in initial contact with a crime scene the means for remote, non-contacting, immediate, thorough and unequivocal documentation of the contents of the scene. Measurements of the relative and absolute global positions of object sand victims, and their dispositions within the scene before their relocation and detailed examination, could be made. Resolution must be sufficient to map both small and large objects. Equipment must be able to map regions at varied resolution as collected from different perspectives. Progress is presented in devising methods for collecting and archiving 3D spatial numerical data from crime scenes, sufficient for law enforcement needs, by remote laser structured light and video imagery. Two types of simulation studies were done. One study evaluated the potential of 3D topographic mapping and 3D telepresence using a robotic platform for explosive ordnance disassembly. The second study involved using the laser mapping system on a fixed optical bench with simulated crime scene models of the people and furniture to assess feasibility, requirements and utility of such a system for crime scene documentation and analysis.

Timing and Appearance of Postmortem Root Banding in Nonhuman Mammals

A study was undertaken using nonhuman mammal specimens to better understand environmental influences on postmortem hair root band (PMRB) formation and to see whether PMRBs would occur in nonhuman mammal hairs in a similar fashion to human hairs. Carcasses from surrounding roadways were the primary source of specimens for this study, augmented by donated deceased domestic pets. Sections of pelt from each specimen were placed in controlled environmental conditions while the remainder of the carcass was left in a secure outdoor setting. Hair samples were collected daily from outdoor and control specimens and examined for evidence of PMRBs. Several environmental factors were also recorded on a daily basis. Results demonstrate PMRBs can occur in nonhuman mammal hairs, and they have microscopic characteristics similar to human PMRBs. Factors found to correlate with PMRB formation include postmortem interval, temperature, pH, and the formation and subsequent volatilization of ammonia from the surrounding tissue.

Recognition of computerized facial approximations by familiar assessors

Studies testing the effectiveness of facial approximations typically involve groups of participants who are unfamiliar with the approximated individual(s). This limitation requires the use of photograph arrays including a picture of the subject for comparison to the facial approximation. While this practice is often necessary due to the difficulty in obtaining a group of assessors who are familiar with the approximated subject, it may not accurately simulate the thought process of the target audience (friends and family members) in comparing a mental image of the approximated subject to the facial approximation. As part of a larger process to evaluate the effectiveness and best implementation of the ReFace facial approximation software program, the rare opportunity arose to conduct a recognition study using assessors who were personally acquainted with the subjects of the approximations. ReFace facial approximations were generated based on preexisting medical scans, and co-workers of the scan donors were tested on whether they could accurately pick out the approximation of their colleague from arrays of facial approximations. Results from the study demonstrated an overall poor recognition performance (i.e., where a single choice within a pool is not enforced) for individuals who were familiar with the approximated subjects. Out of 220 recognition tests only 10.5% resulted in the assessor selecting the correct approximation (or correctly choosing not to make a selection when the array consisted only of foils), an outcome that was not significantly different from the 9% random chance rate. When allowed to select multiple approximations the assessors felt resembled the target individual, the overall sensitivity for ReFace approximations was 16.0% and the overall specificity was 81.8%. These results differ markedly from the results of a previous study using assessors who were unfamiliar with the approximated subjects. Some possible explanations for this disparity in performance were examined, and it was ultimately concluded that ReFace facial approximations may have limited effectiveness if used in the traditional way. However, some promising alternative uses are explored that may expand the utility of facial approximations for aiding in the identification of unknown human remains.

Stature estimation using measurements of the cranium for populations in the United States

Stature estimation is an important component of the biological profile. Human crania are sometimes recovered in the absence of other skeletal material in forensic casework, and stature estimation equations using cranial measurements have not been developed for populations in the United States. Both simple and multiple regression equations for estimating stature were developed from standard cranial measurements taken from both a cranial CT dataset and the Forensic Data Bank, and the resulting equations were tested using a separate dataset. A weak to moderate correlation with stature was found for some of the measurements tested. Tests of the sex- and ancestry-specific equations and pooled sex equations produced accurate estimated stature ranges for most of the individuals in the test dataset, but large 95% confidence intervals (±14-16cm) for these equations can produce only an imprecise estimated stature range for an unidentified individual. Pooled ancestry equations also produced accurate estimated stature ranges for many of the individuals in the test dataset, but with even larger 95% confidence intervals (±18-20cm). The results of this study indicate that stature can be estimated using cranial measurements, but the resulting 95% confidence intervals produce stature ranges that are too broad to use in most forensic casework.