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Michael W. Kenyhercz, PhD Alexandra R. Klales, PhD Christopher W. Rainwater, MS Sara Fredette, BS z The Optimized Summed Scored Attributes Method for the Classification of American Blacks and Whites: A Validation Study Ancestry is difficult to estimate in forensic contexts Pervasive use of non-metric traits in forensic anthropology today Hefner & Ousley (2014) • Developed the OSSA method (Optimized Summed Scored Attributes) • 6 non-metric traits (Figure 1) ordinally scored each trait score is converted to a binary score and then all traits are summed • Summed scores ≤ 3 are classified as Black and summed scores ≥ 4 as White • Method currently being used in forensic casework Discussion & Conclusions Table 1. Sample demographics by institution. Sample Methods 1 Introduction Modern sample trait frequencies (DAFS, OCME) show more overlap than the older HTH sample Adjusting sectioning point to 4 increases total correct classifications Appears to reduce a White classification bias Possible explanations: Secular change Increased admixture Suggestions for application to modern forensic cases: Adjust sectioning point to 4 Be familiar with the trait definitions and scores Remain cognizant of range of human variation Test the validity and reliability of the OSSA Method Determine if a new sectioning point is more appropriate for modern forensic cases Research Goals 274 crania of American Black and White individuals (Table 1) • Historic: Hamann-Todd collection (n=208) • Modern: positively identified forensic cases from the Dept. Applied Forensic Sciences at Mercyhurst University (n=28) and the New York City Office of the Chief Medical Examiner (n=38) Sexes pooled in accordance with Hefner & Ousley (2014) Six traits were scored based on the figures and descriptions from Hefner (2009) Trait frequencies tabulated Classification accuracy tested using OSSA Heuristic adjustment of cut-off scores to maximize classification accuracy for the current sample Results Ancestry/Sex Group HTH DAFS OCME Total Black Females (BF) 52 5 4 61 White Females (WF) 54 7 9 70 Black Males (BM) 50 0 6 56 White Males (WM) 52 16 19 87 Figure 1. Six traits from Hefner (2009) used in the OSSA Method developed by Hefner and Ousley (2014). Results continued Sample Sectioning Point % Correct Black % Correct White Total Correct Classification (%) HTH 3 50.5 85.0 68.3 DAFS 3 20.0 82.6 71.4 OCME 3 70.0 96.4 89.5 HTH 4 80.2 69.2 77.9 DAFS 4 60.0 95.7 92.6 OCME 4 90.0 96.4 94.7 ANS INA IOB 1 2 3 1 2 3 4 5 1 2 3 B W B W B W B W B W B W B W B W B W B W B W HTH 17.8 7.5 54.5 49.5 27.7 43.0 10.9 1.9 27.7 5.6 40.6 27.1 15.8 48.6 4.9 16.8 15.8 43.9 34.6 39.3 48.5 16.8 DAFS 0.0 0.0 100 15.0 0.0 85.0 25.0 0.0 25.0 0.0 25.0 10.0 25.0 50.0 0.0 40.0 25.0 30.0 25.0 65.0 50.0 5.0 OCME 54.5 12.9 27.3 35.5 18.2 51.6 18.2 0.0 18.2 0.0 45.5 3.2 18.2 41.9 0.0 54.8 9.1 41.9 36.4 54.8 54.5 3.2 NAW NBC PBD 1 2 3 0 1 2 3 4 0 1 B W B W B W B W B W B W B W B W B W B W HTH 2.0 27.1 51.5 58.9 46.5 14.0 7.9 0.9 17.8 13.1 5.9 0.0 26.7 52.3 41.6 33.6 49.5 62.6 50.5 37.4 DAFS 0.0 50.0 75.0 50.0 25.0 0.0 0.0 0.0 0.0 0.0 25.0 20.0 50.0 55.0 25.0 25.0 75.0 90.0 25.0 10.0 OCME 18.2 58.1 54.5 41.9 27.3 0.0 72.7 0.0 9.1 12.9 0.0 3.2 9.1 61.3 9.1 22.6 81.8 96.8 18.2 3.2 Figure 2. Distribution of OSSA scores by ancestry with each group’s mean shown as a vertical checkered line. Table 2. Trait frequencies by ancestry and sample. OSSA score distributions higher than reported by Hefner & Ousley (2014) (Figure 2) Adjusting sectioning point to 4 increases total correct classification in each sample (Table 3) Table 3. Correct classifications for each sample using the suggested (3) and adjusted (4) sectioning points. z Acknowledgements Thanks go to Dr. Dennis Dirkmaat of Mercyhurst University and Lyman Jellema of the Cleveland Museum of Natural History for access to the collections used in this research. Thanks also go to Dr. Joseph Hefner for comments on this research. For a full list of references or a copy of the poster, contact: [email protected]
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