Development and validation of a systematic approach for the quantitative assessment of the quality of duct tape physical fits. (February 2020)

• Record Type: Journal Article
• Authors: Prusinowski, Meghan; Brooks, Evie; Trejos, Tatiana
• Is Part Of: Forensic science international. Volume 307(2020)
• Publication Date: 2020-02
• Subjects: Physical end matching -- Fracture fits -- Similarity scores -- Error rates -- Score-based likelihood ratios; Medical jurisprudence -- Periodicals; Chemistry, Forensic -- Periodicals; Forensic Medicine -- Periodicals; Médecine légale -- Périodiques; Chimie légale -- Périodiques; Gerechtelijke geneeskunde; Gerechtelijke chemie; Gerechtelijke psychiatrie; Chemistry, Forensic; Medical jurisprudence; Electronic journals; Periodicals; Electronic journals; 614.1
• DOI: 10.1016/j.forsciint.2019.110103
• Languages: English
• ISSNs: 0379-0738

Abstract

Graphical abstract: Highlights: Similarity metrics permit quantitative assessment of quality of a duct tape fit. Systematic observations based on smallest comparison bin between every warp scrim. Scores inform the examiner's opinion and provide transparent peer-review process. Error rates reported for various tape quality, stretching, and separation methods. Abstract: Duct tape is a common type material found at crime scenes such as sexual assaults, murders, kidnappings, and bombings. During the examination of a known and questioned item, a 3D realignment along their edges is known as a physical fit and is often regarded as conclusive evidence that the items were once part of a single object. The conclusion of a fit between edges relies on the examiner's judgment to identify distinctive features across the tape ends. However, there are currently no consensus-based methodologies or standards to inform their opinions. This study developed a practical method to qualify and quantify tape end match features using edge similarity scores (ESS) and provided an empirically demonstrable basis to assess the significance of duct tape fracture fits. ESS were calculated as the proportion of observed matching sections per scrim bins across the fractured edge, providing a quantifiable criterion and means for a systematic peer review process. A set of 2280 duct tape end comparisons were analyzed for the validation study. The probative value of physical fits was evaluated through similarity metrics, error rates, and score-based likelihood ratios. The effects of separation method, stretching, and tape grade on the distribution of ESS and the overall accuracy are reported. The accuracy ranged from 84.9 % (higher quality hand-torn set) to over 99 % (low and mid-quality sets). No false positives were reported for any of the sets examined. On average, ESS higher than 80 % provided a score likelihood ratio (SLR) that supported the conclusion of a match, and ESS lower than 25 % provided an SLR supporting the conclusion of non-match.