Abstract：
Forensic toolmark examiners compare marks between those observed on an item/surface and those made by a reference implement, such as a particular tool or weapon, to provide an opinion of the likelihood of common origin. It is widely accepted that such comparison opinions need to be underpinned by empirical research, and this study aimed to add to the knowledge base relied upon when developing and comparing saw marks in bone, a substrate encountered in body dismemberment cases. Porcine bones were used as a human proxy; they were either fresh with residual soft tissue and bodily fluids present (\'wet\') to replicate dismembered bones shortly post-mortem, or processed to remove soft tissue and moisture content (\'dry\') to represent cases of dismemberment after an extended period of decomposition and exposure. The bones were cut using one implement of each of five classes: hand saw, mitre saw, reciprocating saw, oscillating saw, and serrated knife. They were cut, either completely through (except for serrated knife), giving two surfaces per cut to examine, or to a depth up to 3 mm (false starts). Five replicates per combination of bone condition, saw, and cut type gave 130 bone samples. These were then cleaned and cast using Isomark Silicone Polymer Compound or Mikrosil, giving 260 cast samples. All bone and cast samples were photographed, examined for various class characteristic markers, and specific markers measured. No significant differences between Isomark and Mikrosil casts were observed when compared side-by-side, demonstrating suitability of both materials for casting of saw marks on bone. Although saw marks presented more class characteristic markers on dry than wet bones, calculations of tooth distances and measurements of kerf width (KW) from marks did not significantly differ between bone conditions, with exception of the reciprocating saw that produced false start marks with significantly larger minimum KW on wet than dry samples. Further analysis supported that tooth distances on marks made by hand and oscillating saws are sufficiently accurate for the determination of saw teeth per inch (TPI). However, one tooth distance on marks made by reciprocating saws did not accurately represent TPI. Finally, examination of presence or absence of class characteristic markers on each saw mark demonstrated consistent variation between saw classes. These results enabled the development of exclusion-based decision trees, and a reference database (available on request), for use by toolmark examiners in their evaluation of saw types based on class characteristic markers observed in cut bone.
摘要：
法医工具标记审查员将在物品/表面上观察到的标记与参考工具所做的标记进行比较，例如特定的工具或武器，提供共同起源的可能性的意见。人们普遍认为，这种比较意见需要以实证研究为基础，这项研究旨在增加在开发和比较骨骼中的锯痕时所依赖的知识库，身体肢解病例中遇到的基质。猪骨被用作人类代理;它们要么是新鲜的，有残留的软组织和体液存在（“湿”）以在死后不久复制肢解的骨头，或处理以去除软组织和水分含量（“干”），以代表长时间分解和暴露后肢解的情况。使用五个类别中的每一个工具切割骨头：手锯，Mitresaw,往复锯,摆动锯,锯齿刀。他们被割伤了,要么完全通过（锯齿刀除外），给每个切口两个表面进行检查，或深度达3毫米（假开始）。每种骨骼状况的组合重复五次，锯,切割类型给出了130个骨骼样本。然后将它们清洁并使用isomark有机硅聚合物化合物或Mikrosil浇铸，给出260个铸造样品。所有的骨头和石膏样本都被拍照,检查各种类别的特征标记，和测量的特定标记。并排比较时，未观察到Isomark和Mikrosil铸型之间的显着差异，证明两种材料在骨骼上铸造锯痕的适用性。尽管锯痕在干骨上比在湿骨上表现出更多的类别特征标记，根据标记计算牙齿距离和测量切口宽度（KW）在骨骼条件之间没有显着差异，除了往复锯产生假起始标记外，湿样品的最小KW明显大于干样品。进一步的分析支持，由手锯和摆动锯制成的标记上的齿距对于确定每英寸锯齿（TPI）足够准确。然而,往复锯标记上的一个齿距不能准确表示TPI。最后,检查每个锯标记上是否存在类别特征标记，表明锯类别之间存在一致的差异。这些结果使得基于排除的决策树的开发成为可能，和一个参考数据库（可根据要求提供），供工具标记检查者根据在切割骨中观察到的类别特征标记评估锯类型时使用。
