Stephen P. Nawrocki

Using Accumulated Degree-Days to Estimate the Postmortem Interval from Decomposed Human Remains

Forensic anthropologists often rely on the state of decomposition to estimate the postmortem interval (PMI) in a human remains case. The state of decomposition can provide much information about the PMI, especially when decomposition is treated as a semi-continuous variable and used in conjunction with accumulated-degree-days (ADD). This preliminary study demonstrates a supplemental method of determining the PMI based on scoring decomposition using a point-based system and taking into account temperatures in which the remains were exposed. This project was designed to examine the ways that forensic anthropologists could improve their PMI estimates based on decomposition by using a more quantitative approach. A total of 68 human remains cases with a known date of death were scored for decomposition and a regression equation was calculated to predict ADD from decomposition score. ADD accounts for approximately 80% of the variation in decomposition. This study indicates that decomposition is best modeled as dependent on accumulated temperature, not just time.

Reconsidering the auricular surface as an indicator of age at death.

Using standards established by Lovejoy et al. to estimate age at death from auricular surface morphology, 266 individuals of documented age, sex, and ancestry from the Terry and Bass Donated Collections were scored. Analysis of covariance (ANCOVA) indicates that for the factors that could be controlled, age is the sole influence on auricular surface morphology. Ancestry and sex had no significant effect on auricular phase expression. No evidence of secular changes was detected when comparing the Terry Collection (early 20th century) to the Bass Collection (later 20th century). Pearson correlations reveal that several of the subcomponents of the auricular surface (superior and inferior demifaces, left and right sides, transverse organization, texture) correspond with age equally well, although a combined scoring of all features performs slightly better than any one indicator taken alone. Not surprisingly, only 33% of the sample was correctly aged when using the 5-year age ranges provided by Lovejoy et al., suggesting that the published ranges are much too narrow to be used in forensic contexts. To assess the variation in age per phase, standard descriptive statistics and error ranges were calculated and can be employed by forensic anthropologists when estimating the age of an unidentified decedent. Because the mean ages of some of the eight phases did not differ significantly from one another, a modified six-phase system is presented. The auricular surface performs as well as any other single skeletal indicator of adult age. This research suggests that a statistically-informed approach should be taken in order to fully understand the drawbacks and limitations of any aging method.

Variation in midfacial tissue thickness of African-American children.

Forensic anthropologists use facial reconstruction to develop a likeness of an unknown individual in order to generate public interest that may lead to a positive identification. Tissue thicknesses of the face from living persons or cadavers are an essential part of the reconstruction method. The purpose of this study is to add to the growing database of tissue thicknesses along the facial midline of African-American children and to begin to examine the possibility of geographic differences between children of the same ancestral group. Results indicate that significant differences do not exist between males and females or between African-American females from the Midwest and Southeast U.S. Only age was determined to have a significant effect on mean tissue thickness variation, in our sample, with the majority of change occurring in the facial region.

Application of FORDISC 3.0 to explore differences among crania of North American and South African blacks and whites.

Using discriminant function analysis, classification accuracies for ancestry and sex in white and black South Africans were compared using North American (FDB), African groups in Howells (HDB), and South African (SADB) databases in FORDISC 3.0. (FD3). Twenty‐four standard linear measures were collected from a total of 86 black and 101 white crania obtained from the Pretoria Bone Collection. White and black South Africans classified 73% correctly in FDB, 55% correctly in HDB, and 71% correctly in SADB. The percentage of atypical cases was higher with FDB than SADB. In all three databases, misclassification occurred more with sex than ancestry revealing differences in sexual dimorphism between population groups. Broad ancestral differences may explain low misclassification rates for ancestry. FD3, with a modern South African reference sample, can assist South African anthropologists to standardize methodology and to justify procedures for estimating ancestry.

Obtaining fingerprints from mummified fingers: a method for tissue rehydration adapted from the archeological literature.

Our laboratory was asked to help with the rehydration of mummified human fingertips that had been removed from a recently deceased, unidentified female. Using a solution that was found in the archeological literature, we were able to successfully rehydrate dermal tissues to the extent that fingerprints could be taken. We believe that this solution, which until now has not been described in the forensic literature, is effective, affordable, and relatively easy to produce and use.

A TAPHONOMIC ANALYSIS OF HUMAN CREMAINS FROM THE FOX HOLLOW FARM SERIAL HOMICIDE SITE

Publisher Summary The Fox Hollow Farm assemblage presented numerous difficulties for the forensic anthropologists involved in the recovery and analysis. The study examined in this chapter is conducted to help shed light on the behavioral (assailant-induced) and environmental factors that altered the remains in the postmortem interval. The goal is to determine whether the physical characteristics of the cremains could indicate if at least some of the victims were burned in a fleshed or dry state even though the fragments had been transported and buried subsequent to burning. Fox Hollow remains are compared to five other samples of burned bones, at least four of which were known to have been burned or cremated in a fleshed state. These five samples experienced different postburning histories, including plowing, excavation, commercial pulverizing, and anatomical study. Some were collected quickly after death, while others had been buried. The Fox Hollow remains do display fractures that are associated with burning of fresh or fleshed remains, including deep transverse, longitudinal and curvilinear fractures, delamination, and warping. However, the occurrence of the fracture types in the Fox Hollow sample is considerably lower than that displayed by most of the other samples. By itself, this evidence would seem to suggest that a larger number of Fox Hollow victims were burned in a dry state than in a fleshed state.

Human Skeletal Variation and Forensic Anthropology

Abstract Forensic anthropology, as a branch of human biology, is grounded in the study of human anatomical and physiological variability. However, because forensic practitioners use variability primarily to make predictions about unidentified individuals, we frequently forget the broader goals of anthropological research. Our experimental models and statistical tests are commonly subpar, with poor sampling strategies, overreliance on univariate and bivariate techniques, and an underappreciation of interactions. We should strive to clearly articulate the variance equations that underlie our work and return to basic hypothesis-testing techniques, which will help to inject more rigor into our studies of human skeletal variability. Forensic anthropologists are, at their core, human biologists: they study the nature and degree of variation in the human body. This focus on variability—as seen across the life span, between populations, and across evolutionary time—is distinctive and inherited from deep anthropological roots. Few scientific fields that are concerned with humans have made variability the central theme of their theoretical paradigms. For example, clinical medicine, psychiatry, and even anatomy have traditionally focused on “average” or modal expressions of traits as seen in western industrialized societies, only recently recognizing the importance of global variability in a way that was central to anthropological thought from the fields conception in the 19th century.

Using Elliptical Fourier Analysis to Interpret Complex Morphological Features in Global Populations

Elliptical Fourier analysis (EFA) can be used to describe complex skeletal features in ways that are remarkably similar to how analysts tend to see them with the naked eye. EFA disassembles the shape of a feature and distills it down to its basic subcomponents irrespective of variation in size. The analyst can then examine each subcomponent to determine how independent variables such as sex and ancestry affect the skeletal feature. Analysis of four cranial and pelvic features in a global sample of identified individuals illustrates the utility and application of EFA in forensic anthropology. These studies underscore the importance of environment and geography in human skeletal variation and the overwhelming preponderance of unexplained variability that is usually underestimated by osteologists.

Chapter 13 – A Taphonomic Analysis of Human Cremains from the Fox Hollow Farm Serial Homicide Site

The Fox Hollow Farm assemblage presented numerous difficulties for the forensic anthropologists involved in the recovery and analysis. The study examined in this chapter is conducted to help shed light on the behavioural (assailant-induced) and environmental factors that altered the remains in the postmortem interval. The goal is to determine whether the physical characteristics of the cremains could indicate if at least some of the victims were burned in a fleshed or dry state even though the fragments had been transported and buried subsequent to burning. Fox Hollow remains are compared with five other samples of burned bones, at least four of which were known to have been burned or cremated in a fleshed state. These five samples experienced different postburning histories, including plowing, excavation, commercial pulverising and anatomical study. Some were collected quickly after death, while others had been buried. The Fox Hollow remains do display fractures that are associated with burning of fresh or fleshed remains, including deep transverse, longitudinal and curvilinear fractures, delamination and warping. However, the occurrence of the fracture types in the Fox Hollow sample is considerably lower than that displayed by most of the other samples. By itself, this evidence would seem to suggest that a larger number of Fox Hollow victims were burned in a dry state than in a fleshed state.