Angi M. Christensen

The Impact of Daubert: Implications for Testimony and Research in Forensic Anthropology (and the Use of Frontal Sinuses in Personal Identification)

This paper emphasizes the need for objectivity and standardized methodologies in the forensic sciences, particularly physical anthropology. To this end, a review of important events in scientific evidence admissibility law, particularly the standards set in the case of Daubert v. Merrell-Dow Pharmaceuticals, Inc., 1993, is presented. The method of confirming a putative identification by visual comparison of antemortem and postmortem frontal sinus radiographs is examined in light of current admissibility standards. The technique is revealed to have a number of shortcomings, including a lack of empirical testing, no estimates of potential error rates, no standards controlling the techniques operation, and no objective determination standards. These shortcomings may, in some instances, prevent resulting conclusions from being admissible evidence. It is suggested that some methods (including frontal sinus comparison) may require more rigorous testing in order to meet these new and stricter standards.

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.

Testing the Reliability of Frontal Sinuses in Positive Identification

The use of frontal sinus radiographs in positive identification has become an increasingly applied and accepted technique among forensic anthropologists, radiologists, and pathologists. From an evidentiary standpoint, however, it is important to know whether frontal sinus radiographs are a reliable method for confirming or rejecting an identification, and standardized methods should be applied when making comparisons. The purpose of the following study is to develop an objective, standardized comparison method, and investigate the reliability of that method. Elliptic Fourier analysis (EFA) was used to assess the variation in 808 outlines of frontal sinuses by calculating likelihood ratios and posterior probabilities from EFA coefficients. Results show that using EFA coefficient comparison to estimate the probability of a correct identification is a reliable technique, and EFA comparison of frontal sinus outlines is recommended when it may be necessary to provide quantitative substantiation for a forensic identification based on these structures.

Validation of X-Ray Fluorescence Spectrometry for Determining Osseous or Dental Origin of Unknown Material*

Abstract:  Forensic anthropological examinations typically involve the analysis of human skeletal remains, but in cases where samples are very small and/or physically compromised, it may first be necessary to determine whether the material is even osseous or dental in origin. X‐ray fluorescence spectrometry (XRF) is a technique that reveals the elemental composition of materials and is hypothesized to have utility in such cases. XRF analysis was conducted on a variety of tissues and materials in unaltered and altered (damaged) states. With few exceptions, osseous and dental tissues in unaltered and altered conditions contained characteristic levels of calcium and phosphorus, while other materials did not. Materials could be accurately identified as osseous or dental in origin based on the calcium and phosphorus levels identified by XRF, and we therefore conclude that XRF analysis is a valid and effective means of determining osseous or dental origin of unknown material.

Factors influencing osteological changes in the hands and fingers of rock climbers

This study examines the osteological changes in the hands and fingers of rock climbers that result from intense, long‐term mechanical stress placed on these bones. Specifically, it examines whether rock climbing leads to metacarpal and phalange modelling in the form of increased cortical thickness as well as joint changes associated with osteoarthritis. This study also attempts to identify specific climbing‐related factors that may influence these changes, including climbing intensity and frequency of different styles of climbing. Radiographs of both hands were taken for each participant and were scored for radiographic signs of osteoarthritis using an atlas method. Total width and medullary width were measured directly on radiographs using digital calipers and used to calculate cross‐sectional area and second moment of area based on a ring model. We compared 27 recreational rock climbers and 35 non‐climbers for four measures of bone strength and dimensions (cross‐sectional area, second moment of area, total width and medullary width) and osteoarthritis. A chi‐squared test for independence was used to compare climber and non‐climber osteoarthritis scores. For each measure of bone strength climbers and non‐climbers were compared using a manova test. Significant manova tests were followed by principal components analysis (PCA) and individual anova tests performed on principal components with eigenvalues greater than one. A second PCA was performed on the climber subsample and the first principal component was then used as the dependent variable in linear regression variable selection procedures to determine which climbing‐related variables affect bone thickness. The results suggest that climbers are not at an increased risk of developing osteoarthritis compared with non‐climbers. Climbers, however, do have greater cross‐sectional area as well as second moment of area. Greater total width, but not meduallary width, indicates that additional bone is deposited subperiosteally. The strength of the finger and hand bones are correlated with styles of climbing that emphasize athletic difficulty. Significant predictors include the highest levels achieved in bouldering and sport climbing.

The Influence of Behavior on Freefall Injury Patterns: Possible Implications for Forensic Anthropological Investigations

Case studies of freefall injuries suggest that most falls from heights result in lower extremity, pelvic, and vertebral fractures. These injuries are largely a consequence of the fact that most falls are accidental with victims landing feet first. This study investigates whether human behavioral response affects body orientation at impact and whether the human body tends to align in a particular way as a result of physical laws. The investigation was undertaken by observing nine experimental falls of an anthropomorphic dummy from a height of 65 ft (9.8 m). In all nine falls, the dummy landed horizontally, suggesting that the human form has a tendency to align horizontally during freefall for falls greater than 50 ft (15.24 m). This has important implications for the potential use of injury patterns in the deduction of pre-fall circumstances, which are discussed here with respect to a case study of a fall victim.

The Reliability of Visually Comparing Small Frontal Sinuses

Abstract:  Several studies have investigated frontal sinus comparison for personal identification. One study addressed the statistical reliability of correct identification using automated digital methods and resulted in a 96% accuracy rate. Missed matches with the digital methods generally involved small, less featured sinuses. This study investigates the hypothesis that human examiners may be able to more accurately identify correct matches than digital methods, even when the comparisons involve small frontal sinuses. Participants were provided two sets of 28 radiographs and were instructed to identify matching radiographs and list the radiographs that did not have a corresponding match. Overall, error rates were low, with correct associations identified at a rate of 0.983. No incorrect associations (“false positives”) were made. Correct association rates were highest among participants “experienced” examining radiographs. Results support previous assertions that frontal sinus radiographs are a reliable means of personal identification even when the frontal sinuses are small.

Techniques for siding manual phalanges

Identifying the anatomical origin of skeletal elements is a basic and important part of a forensic anthropological investigation, but techniques for determining the side and ray of the phalanges are conspicuously scarce in the physical anthropology literature. Features of particular phalanges are important to aspects of archaeological and paleoanthropological studies, as well as for identification and trauma analysis in forensic cases. Correct siding of phalanges may therefore be quite critical in certain contexts. This study evaluates several siding techniques previously developed and/or described in a recent study by Case and Heilman (2000). Unlike in their study where observers were provided all phalange positional information except for side, observations in this study were undertaken with no positional information provided thus making the examinations more similar to those performed in a forensic context. Tests of phalange siding techniques were carried out on two skeletal samples: the Terry Collection at the Smithsonians National Museum of Natural History where the ray and side of phalanges are documented and phalange collections are often complete, and the Bass Collection at the University of Tennessee where phalange positional information is undocumented and where phalange collections are seldom complete. The features described by Case and Heilman were found to work quite well. In the documented (Terry) sample, there was a high rate of correct siding, up to 100% for several phalanges. In the undocumented (Bass) sample, the features could be used to side the phalanges to a reasonable degree of certainty, and certainty increased when both sides of a particular phalange were present. Finally, several other useful siding and ray identification features were identified.

The application of NIST's Fire Dynamics Simulator to the investigation of carbon monoxide exposure in the deaths of three Pittsburgh fire fighters.

A case is reported in which computer fire modeling was used to reevaluate a fire that killed three fire fighters. NISTs Fire Dynamics Simulator (FDS) was employed to model the fire in order to estimate the concentration of carbon monoxide present in the dwelling, which was the immediate cause of death of two of the fire fighters, who appear to have removed their face pieces in order to share available air. This estimate, along with an assumed respiration volume and known blood carboxyhemoglobin, was plugged into a standard equation to estimate the time of exposure. The model indicated that 27 min into the fire, the carbon monoxide concentration had already reached approximately 3600 ppm. At this concentration, and a respiration of 70 L/min, an estimated 3 to 8 min of exposure would have been required to accumulate the concentrations of carboxyhemoglobin (49, 44, and 10%) measured on the fire fighters at autopsy.

Calcium and Phosphorus Detection Using Benchtop Versus Handheld X‐ray Fluorescence Spectrometers

Elemental analysis of calcium (Ca) and phosphorus (P) has been shown to be useful in differentiating skeletal and nonskeletal material. X‐ray fluorescence spectrometry (XRF) is an attractive, nondestructive technique for forensic anthropologists, and the development of portable XRF instrumentation is promising for field applications. This study examines the performance of handheld XRF instrumentation operated in air compared to a traditional benchtop XRF device that has the ability to control the analysis atmosphere. Both instruments can be used to effectively distinguish skeletal from nonskeletal remains. However, as the measurement atmosphere affects detection levels for calcium and phosphorus, Ca/P ratios obtained from the instruments and analysis conditions were found to differ significantly, with analyses conducted in air showing significantly lower phosphorus detection. Consequently, comparison of Ca/P ratios to conclude skeletal versus nonskeletal origin must be based on data collected under similar analysis conditions.