A validation study for duct tape end matches

Fracture matches are considered to be the strongest association achievable in forensic examinations of glass, metal, wood, plastic, paint, tape, and other trace evidence. Despite being fairly routine examinations, few publications exist to support their admissibility in court. This study was designed, using duct tape as the fractured medium, to determine the validity and error rate associated with conducting end match (fracture match) examinations on this material. Five test designs, which varied either the source roll of tape or manner of separation (torn or cut) from the roll, were administered to four analysts with instructions to examine the assigned test sets for end matches. If an end match was not identified by the initial analyst, the entire test set was independently evaluated by the remaining three analysts. Results indicated that while tape grade did not hinder end match identification, the manner of separation could affect results.     

A validation study for vinyl electrical tape end matches

Fracture matches are considered the strongest conclusion in the forensic examination of rigid materials, such as glass, metal, and paint. However, publications that support the fracture matching of polymeric films, such as tape backings, are limited. This study was designed to determine the validity and error rate associated with conducting end-match (fracture match) examinations on vinyl electrical tape. Test designs varied the source roll of tape, test preparer, or mode of separation from the roll. Results indicated that each affected the resulting severed tape ends. The analysts examining the end matches also had an effect on the results. Eight end matches in the study were not identified by the initial analysts and were considered inconclusive. One end match was misidentified, resulting in one false positive and an error rate of 0.049%. These results support a comprehensive physical and chemical tape comparison regardless of indications of an end match.     

Evidentiary Standards for Forensic Anthropology*

Abstract: As issues of professional standards and error rates continue to be addressed in the courts, forensic anthropologists should be proactive by developing and adhering to professional standards of best practice. There has been recent increased awareness and interest in critically assessing some of the techniques used by forensic anthropologists, but issues such as validation, error rates, and professional standards have seldom been addressed. Here we explore the legal impetus for this trend and identify areas where we can improve regarding these issues. We also discuss the recent formation of a Scientific Working Group for Forensic Anthropology (SWGANTH), which was created with the purposes of encouraging discourse among anthropologists and developing and disseminating consensus guidelines for the practice of forensic anthropology. We believe it is possible and advisable for anthropologists to seek and espouse research and methodological techniques that meet higher standards to ensure quality and consistency in our field.     

Metric assessment of the "mastoid triangle" for sex determination: a validation study

Recently, a metric approach to skeletal sex determination was published by Paiva and Segre which is based on the summation of two triangular areas defined by three distinct craniometric landmarks: Porion, Mastoidale, and Asterion. According to the authors, values for the total triangle > or =1447.40 mm(2) are characteristic for male crania, while values < or =1260.36 mm(2) are indicative of female skulls (95% confidence). In order to evaluate the method's validity, two sex- and age-documented samples of different provenience were analyzed (N=197). The results show that while the indicated measurements display significant sex differences, the technique is of little practical meaning where a single individual must be independently classified. It is hypothesized that differences in the expression of sexual dimorphism as well as a population-specific variability of the asterion location undermine the value of the mastoid triangle as a sex determinant.     

Estimating the timing of long bone fractures: correlation between the postmortem interval, bone moisture content, and blunt force trauma fracture characteristics*

There is very limited knowledge about how long perimortem fracture characteristics persist into the postmortem interval (PMI). Therefore, in this study, 60 porcine long bones were exposed to natural taphonomic conditions and fractured with a steel bone breaking apparatus every 28 days throughout a 141-day period. Differences between macroscopic blunt force trauma fracture characteristics (fracture angle, surface morphology, and outline) were examined to determine if they varied over time or in relationship to bone moisture content (ash weight) and overall assessment. There are significant relationships between (1) PMI and percent ash weight (%AW), fracture surface, and fracture angle and (2) %AW and fracture surface and fracture angle. Bone moisture content correlates significantly with fracture morphology and other characteristics commonly used by forensic anthropologists to determine the timing of traumatic injuries. However, fracture characteristics normally associated with perimortem trauma can persist long into the PMI.     

Assessment of intra- and intercostal variation in rib histomorphometry: its impact on evidentiary examination

Rib histological age estimation requires the evaluation of the middle third of the sixth rib. Human ribs have thin cortices and, when recovered, are often fragmented or absent, making it difficult to identify a specific midthoracic rib. This research explores the amount of microstructure variation in the middle third of the midthoracic ribs and determines whether the sixth rib age prediction equation can be applied to non-sixth ribs with similar accuracy. The amount of variability must be evaluated in order to meet the criterion for evidentiary examination. The sample consists of 120 cortical bone cross-sections from the middle third of ribs 3-8 removed from 20 cadavers. For each rib, osteon population densities (OPDs) and associated age estimates were calculated. The results demonstrate that non-sixth ribs can provide similar OPD values compared with those of the sixth ribs; however, individual variation proved to be significantly associated with bias, suggesting that individual factors influence the magnitude and direction of bias in non-sixth rib OPD values. This demonstrates the importance of evaluating multiple cross-sections (both intra- and inter-rib) to estimate age due to the normal remodeling variation within individuals.     

Physical Matching of Metals: Grain Orientation Association at Fracture Edge

The objective of this study was to examine whether surface crystal orientation can be used to associate or differentiate metal fracture fragments. The orientations of individual crystals and crystals across the fracture plane were measured on polished steel and iron alloy surfaces using Electron Backscattered Diffraction/ Orientation Imaging Microscopy (EBSD/OIM). This investigation examined crystallographic characteristics within a metal. This study showed that for transgranular fracture, it is feasible that pieces of grains could be associated across the fracture surface with the difference in orientation between grains (misorientation) along a length sequence of grain orientations on one side of the fracture surface to associate the other side of a fracture surface. Regarding pair comparisons of crystals on fracture surfaces, it was estimated that the probability for an ordered sequence of six distinct oriented grains along a fracture surface to occur again is about 1 in 4.82 (10)³⁰ or 2.07 (10)⁻³¹.     

Frozen human bone: a microscopic investigation

The taphonomic effects of prolonged extreme cold and freezing on human bone have received little research attention. Questions of specific interest include whether previously frozen bone can be identified and whether freezing alters the structural integrity enough to prevent histological aging. There is no evidence from previous studies that freezing damages the structural integrity, and to date no research investigating the freezing process on bone microstructure has been undertaken. This research attempts to distinguish histologically previously frozen bone from nonfrozen bone by identifying patterned defects. To determine the effects of freezing in bone microstructure using light and scanning electron microscopy (SEM), several human bone sections were subjected to prolonged freezing and allowed to thaw before thin sectioning. Light microscopy failed to demonstrate statistically significant differences between frozen and nonfrozen specimens. SEM analysis revealed fractures, although these lacked pattern and did not occur systematically throughout the section. Evidence of microstructural changes caused by liquid expansion, however, was remarkable but did not alter the structural integrity of the microstructure. The results of this study suggest that freezing does not alter the process of histomorphological analysis.     

The use of material culture to establish the ethnic identity of victims in genocide investigations: a validation study from the American Southwest*

Successful prosecution of genocide requires that the victims constitute one of four protected groups: national, religious, ethnic, or racial. Establishing victim identity in prior trials has relied on positive identification of decedents, been largely presumptive, or was based on untested methodology. This report details a validation study of one untested method: the use of material culture in establishing ethnic identity. Classes of clothing and personal effects were scored on 3,430 individuals of known Hispanic or White ancestry from autopsy records in New Mexico. Significant differences were seen in evidence of language, nationality, and religious affiliation between the two groups, as well as clothing types and currency. Predictive models used to estimate ethnic identity in random, blind subsets produced an overall accuracy of 81.5% and estimates of 61-98% in specific subsets. Results suggest material culture, when present, can provide reliable evidence of ethnic affinity in genocide investigations.     

Taphonomic changes to blunt force trauma: a preliminary study

This study examines the effects of taphonomic processes on blunt force trauma (BFT) through an experimental study involving pig heads. Of particular concern is the possibility that taphonomic changes can create pseudo-trauma and/or conceal evidence of actual trauma. BFT was inflicted on 10 pig skulls using a hammer. The skulls were subsequently exposed to the environment for 12 months. Seven taphonomic changes were evaluated: the freeze-thaw cycle; rodent gnawing; carnivore scavenging; presence/weight of soil; presence/weight of rain and snow; movement/displacement of bones; and discoloration due to sun bleaching and grass staining. Taphonomic effects varied between cancellous, compact, fresh, and degreased bone. Freezing and thawing, exposure to rain and snow, movement of the skulls, and soil erosion altered and, in some cases disguised, pre-existing trauma. Rodent and carnivore activity did not obliterate evidence of BFT. Recommendations for evaluating BFT on remains affected by taphonomic processes are presented. As each taphonomic process outlined by this study has the potential to disguise antemortem injury, the authors propose that one must carefully examine large, circular openings in the skull that may represent the remnant evidence of BFT.     

Kumho, Daubert, and the nature of scientific inquiry: implications for forensic anthropology

In the last 15 years, the US Supreme Court has implemented major changes concerning the admittance of expert testimony. In 1993, Daubert v. Merrell Dow Pharmaceuticals superseded the Frye ruling in federal courts and established judges, not the scientific community, as the gatekeepers regarding the credibility of scientific evidence. In 1999, a lesser-known but equally important decision, Kumho Tire v. Carmichael, ruled that technical expert testimony needed to employ the same rigor as outlined in Daubert, but experts can develop theories based on observations and apply such theories to the case before the court. Anthropology has never been defined as a hard science. Yet, many recent publications have modified existing techniques to meet the Daubert criteria, while none have discussed the significance of Kumho to anthropological testimony. This paper examines the impact of Daubert and Kumho on forensic anthropology and illustrates areas of anthropological testimony best admitted under Kumho's guidance.     

Comparison of handmarks in manual strangulation: an experimental study

A police case with a strangulated woman with fingermarks on the neck and two suspects identifying each other as the perpetrator set off a laboratory experiment. Twenty-one males participated in the study. Blue paint was applied to their fingers, after which they grasped a neck dummy and pressed hard as if strangulating someone. The imprint was removed from the dummy, and their hands were photographed. Five imprints were randomly chosen and superimposed on the hand photographs in blind trials. In no cases did we match an imprint to the correct hand. However, in four cases we matched the imprint with several hands, one of which was the correct one. This means we were able to exclude nonmatches in 4/5 cases. Overall, matching of hands and fingermarks is difficult and inconclusive. Objective criteria for matching are difficult to establish, and matching is probably best suited for cases with specific anatomical features.     

The effects of corrosive substances on human bone, teeth, hair, nails, and soft tissue

Abstract: This research investigates the effects of household chemicals on human tissues. Five different human tissues (bone, tooth, hair, fingernails, and skin/muscle/fat) were immersed into six different corrosive agents. These agents consisted of hydrochloric acid, sulfuric acid, lye, bleach, organic septic cleaner, and Coca‐Cola^® soda. Tap water was used as a control. Tissue samples were cut to consistent sizes and submerged in the corrosive liquids. Over time, the appearance, consistency, and weight were documented. Hydrochloric acid was the most destructive agent in this study, consuming most tissues within 24 h. Sulfuric acid was the second most destructive agent in this study. Bleach, lye, and cola had no structural effects on the hard tissues of the body, but did alter the appearance or integrity of the hair, nails, or flesh in some way. The organic septic cleaner and tap water had no effect on any of the human tissue tested during the timeframe of the study.     

Survival of Atherosclerotic Calcifications in Skeletonized Material: Forensic and Pathological Implications

Atherosclerosis is a chronic inflammatory disease creating calcifying plaques in the arterial walls. Because its paleopathological diagnosis remains little studied on skeletal remains, its impact on forensic and archeological data is completely underestimated. Here, 24 skeletal remains from the Milano Cemetery Skeletal Collection have been studied to evaluate the chance of atherosclerotic calcification survival, retrieval, and identification. Through direct comparison with a known autopsy collection and literature, the identification and categorization of several types of calcifications were performed. Clothing elements such as tights or socks played a definitive role in the preservation of the calcifications; hence they are more likely to be found in forensic cases than in archeological ones. Therefore, vascular calcifications are possible to collect and identify in skeletal remains if sufficient care is given to their recovery. Consequently and as markers of the disease, such identification can provide valuable pathological information for forensic and archeological cases.     

Determination of Sex: Interest of Frontal Sinus 3D Reconstructions

Frontal sinuses (FSs) have been studied in radiology, anthropology, and forensic anthropology. This study aimed to determine whether it was possible to predict the age and sex of an individual using FS volume. Sixty‐nine anonymized CT scans were imported to MIMICS 10.01^® software (Materialise N.V.), and each FS volume was calculated in mm³. There was an absence of significant difference between right and left FS volume (p = 0.173) and an absence of correlation between age and FS volume (Pearson's test; p = 0.705). Sexual dimorphism was significantly different (p = 0.001). However, the most discriminant datum for determining sex was found to be the total FS volume (sum of an individual's right and left FS volumes) with linear discriminant Fisher's function coefficients of ?2.759 for the male group and ?1.275 for the female group. With this model, 72.5% of our sample was correctly classified according to sex.     

The Development and Application of Random Match Probabilities to Firearm and Toolmark Identification

The field of firearms and toolmark analysis has encountered deep scrutiny of late, stemming from a handful of voices, primarily in the law and statistical communities. While strong scrutiny is a healthy and necessary part of any scientific endeavor, much of the current criticism leveled at firearm and toolmark analysis is, at best, misinformed and, at worst, punditry. One of the most persistent criticisms stems from the view that as the field lacks quantified random match probability data (or at least a firm statistical model) with which to calculate the probability of a false match, all expert testimony concerning firearm and toolmark identification or source attribution is unreliable and should be ruled inadmissible. However, this critique does not stem from the hard work of actually obtaining data and performing the scientific research required to support or reject current findings in the literature. Although there are sound reasons (described herein) why there is currently no unifying probabilistic model for the comparison of striated and impressed toolmarks as there is in the field of forensic DNA profiling, much statistical research has been, and continues to be, done to aid the criminal justice system. This research has thus far shown that error rate estimates for the field are very low, especially when compared to other forms of judicial error. The first purpose of this paper is to point out the logical fallacies in the arguments of a small group of pundits, who advocate a particular viewpoint but cloak it as fact and research. The second purpose is to give a balanced review of the literature regarding random match probability models and statistical applications that have been carried out in forensic firearm and toolmark analysis.     

Age estimation of Korean adults by occlusal tooth wear

The aim of the present study was to evaluate the validity of the modified Kim's scoring system as a practical method of recording occlusal tooth wear and estimating age. For this purpose, 1092 pairs of maxillary and mandibular full-arch casts were randomly selected, scored, and analyzed. The results showed that the modified Kim's scoring system had excellent reliability, and that occlusal tooth wear had a positive correlation with age. Tooth wear scores of all teeth except the two lower central incisors were higher in males than in females. Calculating tables for age estimation were designed by multiple linear regression analysis. Estimated ages were within +/-5 years of actual ages in 63.5% of male subjects, and 64.0% of female subjects. The accuracy of age estimation was increased when the subjects were divided into two age groups and data were re-analyzed. Collectively, it was shown that the modified Kim's scoring system is a reliable and accurate method for age estimation, and that the data from these 1092 individuals can be used as a standard for age estimation of Korean adults.     

Role of orthopedic implants and bone morphology in the identification of human remains

When conventional methods of identification, such as visual recognition and dental comparison, cannot be used to identify a deceased person, it becomes necessary to consider alternative methods. The presence of an orthopedic implant in a body may assist identification if ante-mortem medical records are available for comparison. Another method of identification involves comparison of ante-mortem and postmortem radiographs. Eight cases are reported from Forensic Science SA where the presence of orthopedic implants and/or ante-mortem radiographs were used to try to establish identification. In six cases, positive identification was established, and in two cases with upper limb orthopedic implants, the bones remained unidentified. Manufacturers were unable to provide any information about the distribution and use of the implants that could be of use with identification, as there are no requirements in Australia for individual medical implants to be tracked. Such a system has the potential to aid postmortem identification if serial codes were etched onto implants that could then be traced to manufacturers, surgeons, and recipients of these devices.     

法医骨组织学研究

在实际检案中 ,当现场发现的骨骼残片体积较小时 ,用解剖学观察无法进行骨骼残片的法医鉴定 ,需使用骨组织学的方法进行骨骼残片的个体识别。目前 ,这是法医人类学中一门较活跃的领域 ,即法医骨组织学。法医骨组织学的内容主要包括两个方面 :(1)骨骼残片是否属于人类骨骼 ,或属于何种动物骨骼。这方面的研究包括人类骨骼的组织学特征研究及不同动物的组织学特征研究。 (2 )人类骨骼个体识别的组织学研究。这方面的研究主要包括 ,人类骨骼的组织学特征的年龄判断 ,例如股骨、胫骨、肱骨、锁骨等 ,以及使用骨组织学方法 ,进行人类骨骼的年龄评价的准确性研究。本文对上述内容进行了综述。     

A Method for Articulating and Displaying the Human Spine

Abstract:  An inexpensive and effective method for articulating a dry human spine is described. By constructing a Styrofoam™ spine tray, analysts can now accurately position and align each vertebra in correct anatomical order, allow for gaps because of missing vertebrae, and lay out the spine for documentation and photography. The spine tray provides analysts with a quick, easy, and professional quality method for aligning and orienting the human spine in the field and laboratory.