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Assessing significant factors that can influence physical fit examinations - Part I. Physical fits of torn and cut duct tapes

NCJ Number
Forensic Science International Volume: 343 Dated: February 2023 Pages: 111567
Date Published
February 2023

In this examination of the assessment of significant factors that can influence the examination of physical fits of torn and cut duct tapes 1) the proposed 3-step method provides consistent and transparent documentation; 2) the defined comparison criteria offer insight into a given fit/non-fit decision; and 3) statistical assessment demonstrates which factors contribute most to quality of fit.



This study expands upon a previously developed method that quantifies the similarity of the compared tape edges by systematically studying the effect of several separation methods and tape grades on the quality of a fit. Analysts examined more than 3300 pairs of hand-torn or scissor-cut duct tapes from three different tape grades while they were kept blind from the ground truth to minimize bias. The samples were examined following a three-step methodology: 1) qualitative assessment of the overall edge alignment and description of edge pattern, 2) macroscopic evaluation of the edges’ features, 3) bin by bin subunit assessment of tape edges and estimation of the edge similarity score. A report template was designed to maintain records of the decision-making process. In the second and third steps, eight comparison features were defined and documented using auto-populated cell options. Generally, misidentification rates were low, with no false positives reported. Coinciding with previous research, low scores (under 20%) provided the most support for a non-fit conclusion, while high scores (80% or higher) supported a fit conclusion. A statistical analysis of the separation method and quality of tape revealed a potential interaction between these factors and showed that they significantly impact the edge scores for true fitting pairs, but not the true non-fits’ scores. The developed comparison and documentation criteria can assist practitioners with a more straightforward, consistent, and transparent interpretation and reporting approach.  (Published abstract provided)

Date Published: February 1, 2023