Validation of Sherlock, a linear trajectory analysis program for use in bloodstain pattern analysis. Issue 2 (3rd April 2019)

• Record Type: Journal Article
• Authors: Orr, Amanda; Illes, Mike; Beland, Jacques; Stotesbury, Theresa
• Is Part Of: Journal. Volume 52:Issue 2(2019)
• Page Start: 78
• Page End: 94
• Publication Date: 2019-04-03
• Subjects: forensic science -- bloodstain pattern analysis -- impact pattern -- area of origin -- trajectory analysis -- Sherlock -- three-dimensional coordinates -- software validation -- open access -- tangent method; analyse des taches et patrons de sang -- aire d'origine -- analyse de trajectoire -- validation de logiciel -- libre accès -- méthode de la tangente; Chemistry, Forensic -- Periodicals; Criminal investigation -- Periodicals; Periodicals; 363.2506071
• DOI: 10.1080/00085030.2019.1577793
• Languages: English
• ISSNs: 0008-5030

Abstract

Abstract: This research validates the accuracy and efficacy of Sherlock, a recently developed program that estimates the area of origin (AO) of an impact pattern. Sherlock is an open-access, web-based software that conducts trajectory analysis by using the tangent method to estimate the area of origin. Fifty impact patterns were created at known X -, Y -, and Z -coordinates and were analyzed by upper year forensic science undergraduate students at Trent University. Individual stain data collected for each pattern were analyzed by both Sherlock and BackTrack TM /WIN. In this validation, we assess two objectives. The first evaluates the overall accuracy of the Sherlock program and the second compares the AO results between Sherlock and BackTrack TM /WIN when analyzing the same stain data. The average absolute deviation from the known using Sherlock was found to be 5.6 cm for the X -coordinate, 2.3 cm for the Y -coordinate, and 6.6 cm for the Z -coordinate. Further, when comparing the three-dimensional (3D) coordinate vector values, which considers all three coordinates as a single value, the Sherlock and known 3D AOs were shown to be similar with an average absolute deviation of 3.5 cm. Comparison between BackTrack TM /WIN and Sherlock provided statistically similar results for all comparisons ( p > 0.05 in all cases), with average absolute deviations of 0.28 cm, 0.13 cm, and 0.75 cm in the X -, Y -, and Z -coordinates, respectively. This research demonstrates that the accuracy of the Sherlock program is comparable to a previously validated AO analysis program with similar absolute deviation from the true AO for single surface impact patterns.