Comparing Genetic Variation among Latin American Immigrants: Implications for Forensic Casework in the Arizona- and Texas-Mexico Borderlands.

The humanitarian crisis on the US-Mexico border is a long-standing and evolving crisis in which nearly 8,000 deaths have been reported in the last two decades. These deaths are largely distributed across the Arizona-Mexico and Texas-Mexico border regions, where demographic trends for immigrants attempting to cross into the United States have shifted dramatically. The demographic change and volume of immigrants seeking shelter in the United States present new challenges for the forensic practitioners entrusted with the identification of individuals who lose their lives during the final segment of their journey. Within this border context, this study investigated how genetic variation inferred from forensically significant microsatellites can provide valuable information on regions of origin for unidentified remains at the group level. To explore how to mobilize these genetic data to inform identification strategies, the authors conducted a comparative genetic analysis of identified and unidentified immigrant cases from the Arizona- and Texas-Mexico contexts, as well as 27 other Latin American groups. Allele frequencies were utilized to calculate FST, and relationships were visually depicted in a multidimensional scaling plot. A Spearman correlation coefficient analysis assessed the strength and significance of population relationships, and an agglomerative clustering analysis assessed population clusters. Results indicate that Arizona-Mexico immigrants have the strongest relationship (>80%) with groups from El Salvador, Guatemala, Mexico, and an indigenous group from southern Mexico. Texas-Mexico immigrants have the strongest relationships (>80%) with groups from Belize, Colombia, Costa Rica, El Salvador, Guatemala, Honduras, and Nicaragua. These findings agree with, and are discussed in comparison with, previously reported demographic trends, population genetics research, and population history analyses. The authors emphasize the utility and necessity of coupling genetic variation research with a nuanced anthropological perspective for identification processes in the US-Mexico border context.

Use of craniometric data to facilitate migrant identifications at the United States/Mexico border.

OBJECTIVES: Thousands of migrants have died along the United States/Mexico border and many remain unidentified. The purpose of this research is to test whether estimations of population affinity, derived from craniometric data, can facilitate identification of migrant remains and provide a geographic region of origin rather than the broad label Hispanic. The appropriateness of current forensic reference data will also be assessed. METHODS: A case study combined with craniometric data from positively identified and unidentified migrants from the Pima County Office of the Medical Examiner (n = 489) in Arizona and operation identification (n = 201) in Texas were compared to skeletal data representing Guatemalan (n = 87) and Mexican (n = 65) Mayans. Biological distance and discriminant function analyses were used to assess overall population relationships and classificatory models for forensic anthropological application. RESULTS: The majority of evidence indicates that estimations of population affinity can assist in the facilitation identification of migrant remains, even when a broad classification is used. Biological distances among the groups suggest that positively identified Guatemalan and Mexican migrants are similar to one another but differ from Guatemalan and Mexican Mayans. CONCLUSIONS: Population affinity estimations can aid migrant identification, and current reference data used in forensic anthropological practice should be replaced with data from positive identifications. Estimates of geographic origin may be more useful than the broad generic term Hispanic for narrowing down the search for a missing person, but more data and research is needed to achieve this goal. Although, the utility of geographic origin estimates relies on transnational data centralization and sharing, which is not always the case.

Identifying migrant remains in South Texas: policy and practice.

In 2012, Texas surpassed Arizona in migrant deaths. The majority of deaths occurred in the Rio Grande Valley, specifically in Brooks County, Texas. Brooks County is one of the poorest in the state and was overwhelmed with deaths, without appropriate resources to follow the state laws pertaining to the investigation of unidentified human remains. Until 2013, most remains that were not immediately identified were buried without collecting DNA samples and the location of burials was not recorded. Our paper outlines the difficulties searching for these burials, the struggles of the families of the missing, and the collaborative approaches to facilitating identifications in South Texas. Community outreach combined with geophysical surveys guide which cemeteries are in need of exhumations. Once cemeteries are surveyed, archaeological methods are employed to exhume remains and document burials. Remains are taken to the Forensic Anthropology Center at Texas State for processing, analysis, and identification efforts. Undergraduate and graduate students clean remains and wash clothing and personal effects. After skeletal analysis, all information regarding the remains, including photographs of personal effects, are uploaded to the National Missing and Unidentified Persons System (NamUs) and a DNA sample is submitted to the University of North Texas for inclusion in the Combined DNA Index System (CODIS) DNA database. However, CODIS lacks DNA family reference samples from many families of the missing due to families living outside the US or because they do not feel comfortable providing a DNA sample in the presence of law enforcement. Therefore, it is necessary to work with non-governmental organizations who specialize in collecting missing persons reports and DNA samples from the families of the missing. Working collaboratively with multiple agencies, identification of migrant remains is possible.

Demographic change and forensic identification: problems in metric identification of Hispanic skeletons.

The United States (U.S.) population structure is currently in a state of flux with one of the most profound changes being the increasing number of people referred to as Hispanic. In the U.S., much of the identification criteria for a biological profile are based on American Black and White individuals from anatomical collections. Using metric data from the Forensic Anthropology Data Bank (FDB), this paper will attempt to explore several issues that forensic anthropologists face when confronted with Hispanic remains. These will involve estimation of sex, height, and ancestry, the initial components of a biological profile. Discriminant function analyses indicate that American White criteria provide poor estimations of sex when applied to Hispanics and that ancestry estimation of Hispanic crania is difficult. Additionally, a new linear regression equation is presented that estimates stature for Hispanic individuals, although population specific criteria are still needed for Hispanic individuals from diverse geographical origins.

Craniofacial asymmetry as a marker of socioeconomic status among undocumented Mexican immigrants in the United States.

This study examines levels of fluctuating asymmetry (FA) in Mexican residents, U.S. residents, and undocumented border crossers (UBCs) from Mexico to the United States. Craniofacial structures develop symmetrically under ideal circumstances; however, during periods of developmental stress random deviations from perfect symmetry, or FA, can occur. It is hypothesized that the UBC sample would represent individuals of a lower socioeconomic status (SES) who experienced higher stress levels during development, and that these individuals would consequently have higher levels of FA. Three-dimensional cranial landmarks were collected from 509 individuals representing the three resident groups. Geometric morphometric methods were used to calculate an FA score for each individual. The FA score provides a distance measure that is a scalar measure of the magnitude of FA in each individual. The results show that the difference in the means of the FA scores between UBCs and U.S. residents is 0.43 (p = 0.02), with UBCs showing significantly higher levels of FA compared to U.S. residents. Moreover, Mexican residents' FA levels are intermediate between and not significantly different from the other two samples. These results suggest that levels of FA may prove useful for reconstructing individuals' social and economic circumstances, and that craniofacial asymmetry provides a suitable biological marker for analyzing differences in SES among different groups.

Migrant deaths at the Arizona-Mexico border: Spatial trends of a mass disaster.

Geographic Information Science (GIScience) technology has been used to document, investigate, and predict patterns that may be of utility in both forensic academic research and applied practice. In examining spatial and temporal trends of the mass disaster that is occurring along the U.S.-Mexico border, other researchers have highlighted predictive patterns for search and recovery efforts as well as water station placement. The purpose of this paper is to use previously collected spatial data of migrant deaths from Arizona to address issues of data uncertainty and data accuracy that affect our understanding of this phenomenon, including local and federal policies that impact the U.S.-Mexico border. The main objective of our study was to explore how the locations of migrant deaths have varied over time. Our results confirm patterns such as a lack of relationship between Border Patrol apprehensions and migrant deaths, as well as highlight new patterns such as the increased positional accuracy of migrant deaths recorded closer to the border. This paper highlights the importance of using positionally accurate data to detect spatio-temporal trends in forensic investigations of mass disasters: without qualitative and quantitative information concerning the accuracy of the data collected, the reliability of the results obtained remains questionable. We conclude by providing a set of guidelines for standardizing the collection and documentation of migrant remains at the U.S.-Mexico border.

A Longitudinal Study on Human Outdoor Decomposition in Central Texas.

The development of a methodology that estimates the postmortem interval (PMI) from stages of decomposition is a goal for which forensic practitioners strive. A proposed equation (Megyesi et al. 2005) that utilizes total body score (TBS) and accumulated degree days (ADD) was tested using longitudinal data collected from human remains donated to the Forensic Anthropology Research Facility (FARF) at Texas State University-San Marcos. Exact binomial tests examined the rate of the equation to successfully predict ADD. Statistically significant differences were found between ADD estimated by the equation and the observed value for decomposition stage. Differences remained significant after carnivore scavenged donations were removed from analysis. Low success rates for the equation to predict ADD from TBS and the wide standard errors demonstrate the need to re-evaluate the use of this equation and methodology for PMI estimation in different environments; rather, multivariate methods and equations should be derived that are environmentally specific.

Postcranial sex estimation criteria for Mexican Hispanics.

Population-specific reference data are necessary for sex estimation in forensic anthropological practice. Currently, there are no population-specific data for Hispanics equivalent to data available for American Blacks and Whites. Individuals of Mexican origin represent the largest group of Hispanics in the United States (Spradley and Jantz. 2011. J Forensic Sci;56:289). This paper presents new population-specific sex estimation criteria for postcranial measurements for Mexican Hispanics. Metric data come from positively identified border-crossing fatalities at the Pima County Office of the Medical Examiner and documented cemetery collections curated at Universidad Nacional Autónoma de México and Universidad Autónoma de Yucatán. Stepwise variable selection procedures and discriminant function analyses were utilized to generate classification functions for postcrania. Sectioning points were also created for select measurements. Both the cross-validated classification rates and sectioning points achieved accuracy rates as high as 95% and 92%, respectively. These new criteria will improve sex estimation for US Mexico border crossers and Hispanics in the US.

Postcranial sex estimation of individuals considered Hispanic.

When forensic anthropologists estimate the sex of Hispanic skeletal remains using nonpopulation specific metric methods, initial observations cause males to frequently misclassify as female. To help improve these methods, this research uses postcranial measurements from United States-Mexico border migrant fatalities at the Pima County Office of the Medical Examiner in Tucson, Arizona, as well as Hispanic individuals from the Forensic Anthropology Data Bank. Using a total of 114 males and 28 females, sectioning points and discriminant functions provide classification rates as high as 89.43% for Hispanic individuals. A test sample assessed the reliability of these techniques resulting in accuracy up to 99.65%. The clavicle maximum length measurement provides the best univariate estimate of sex, while the radius provides the best multivariate estimated of sex. The results of this research highlight the need for population specific data in the creation of a biological profile, especially when working with individuals considered Hispanic.

Analysis of bone healing in a postoperative patient: skeletal evidence of medical neglect and human rights violations.

This study highlights complexities associated with postsurgical trauma interpretation of a 76-year-old female patient from a psychiatric institution in Mexico. The skeletal analysis identified complications from an unsuccessful surgical operation for an intertrochanteric fracture of the femur. An improperly placed surgical plate resulted in nonunion due to limited contact between fracture margins. However, it is unclear whether this resulted from surgical complications, ineffective postoperative care, or from the decedent's limited ability to follow postoperative care instructions. Additionally, failure of the plate resulted in degenerative changes to the acetabulum. These complications, associated with degenerative changes to upper limb joints, suggest significant mobility issues. The pattern of antemortem trauma and contextual information support a conclusion of postoperative medical neglect, a documented problem in psychiatric institutions in Latin America. This study provides insight into the relevance of detailed trauma assessment of skeletal remains in cases where neglect and human rights violations are suspected.

Estimating sex of the human skeleton based on metrics of the sternum.

Estimating the sex of skeletal remains is critical in creating the biological profile of an adult individual. Previous research has shown that analyzing the sternum may lead to an accurate estimation of sex based on studies performed on various populations around the globe, such as Indian, European, African, Canadian and North American. The motivation of the current study is to develop classification functions and sectioning points for use in forensic investigations in the United States. The majority of previously published methods are population specific, meaning the data would not prove useful in the United States. For this study, sternal measurements were collected from the William M. Bass Donated Skeletal Collection located at The University of Tennessee, Knoxville following the metric definitions provided by Schwartz and Bass. This collection consists of recent skeletal remains with known age at death, ancestry and sex. Material for the present study consisted of 410 human sterna: 285 male (256 American White/29 American Black) and 125 female (120 American White/5 American Black). Previous studies analyze the applicability of Hyrtl's law in the estimation of sex. This law follows that the mesosternum is greater than twice the length of the manubrium in males and in females the length of the manubrium is greater than half the length of the mesosternum. In this study, comparisons of the proportion of the length of the manubrium to the length of the mesosternum were performed to determine if Hrytl's law is applicable in an American population. Comparisons of these measurements between individuals identified as American Black and American White were analyzed to determine whether this method could be used on both population groups. Further, discriminant function analysis was used to estimate sex and provide a population specific classification function for use in the United States. The discriminate function analysis produced an overall cross-validation classification rate of 84.12% for sex estimation. The cross-validation classification rate for males and females was 80.00% and 88.24%, respectively.

Sex estimation in a modern American osteological sample using a discriminant function analysis from the calcaneus.

Reliable methods for sex estimation during the development of a biological profile are important to the forensic community in instances when the common skeletal elements used to assess sex are absent or damaged. Sex estimation from the calcaneus has potentially significant importance for the forensic community. Specifically, measurements of the calcaneus provide an additional reliable method for sex estimation via discriminant function analysis based on a North American forensic population. Research on a modern American sample was chosen in order to develop up-to-date population specific discriminant functions for sex estimation. The current study addresses this matter, building upon previous research and introduces a new measurement, posterior circumference that promises to advance the accuracy of use of this single, highly resistant bone in future instances of sex determination from partial skeletal remains. Data were collected from The William Bass Skeletal Collection, housed at The University of Tennessee. Sample size includes 320 adult individuals born between the years 1900 and 1985. The sample was comprised of 136 females and 184 males. Skeletons used for measurements were confined to those with fused diaphyses showing no signs of pathology or damage that may have altered measurements, and that also had accompanying records that included information on ancestry, age, and sex. Measurements collected and analyzed include maximum length, load-arm length, load-arm width, and posterior circumference. The sample was used to compute a discriminant function, based on all four variables, and was performed in SAS 9.1.3. The discriminant function obtained an overall cross-validated classification rate of 86.69%. Females were classified correctly in 88.64% of the cases and males were correctly classified in 84.75% of the cases. Due to the increasing heterogeneity of current populations further discussion on this topic will include the importance that the re-evaluation of past studies has on modern forensic populations. Due to secular and micro evolutionary changes among populations, the near future must include additional methods being updated, and new methods being examined, both which should cover a wide population spectrum.

Spatial patterning of vulture scavenged human remains.

This article presents the results of a pilot study on the effects of vulture modification to human remains. A donated body from the Willed Body Donation Program was placed at the Forensic Anthropology Research Facility (FARF), an outdoor human decomposition laboratory located at Texas State University-San Marcos. The effects of vulture scavenging on the timing and sequence, and the rate of skeletonization, disarticulation, and dispersal were observed via a motion sensing camera and direct observation. Using GIS (Geographic Information Systems) and GPS (Global Positioning System) technologies and spatial analytical methods, the transport of skeletal elements was mapped in order to analyze dispersal and terrain-influenced patterns of active vulture scavenging. Results showed that the initial scavenging took place 37 days after placement at FARF. This delay in scavenging differs from previous research. After the initial appearance of the vultures, the body was reduced from a fully-fleshed individual to a skeleton within only 5h. This underscores the potential for errors in postmortem interval estimations made at vulture scavenged scenes. Additionally, spatial analysis showed that skeletal elements were dispersed by vultures to lower elevations, and that the disarticulation and dispersal of the skeletal elements occurs early in the scavenging sequence.

Sex estimation in forensic anthropology: skull versus postcranial elements.

When the pelvis is unavailable, the skull is widely considered the second best indicator of sex. The goals of this research are to provide an objective hierarchy of sexing effectiveness of cranial and postcranial elements and to test the widespread notion that the skull is superior to postcranial bones. We constructed both univariate and multivariate discriminant models using data from the Forensic Anthropology Data Bank. Discriminating effectiveness was assessed by cross-validated classification, and in the case of multivariate models, Mahalanobis D(2). The results clearly indicate that most postcranial elements outperform the skull in estimating sex. It is possible to correctly sex 88-90% of individuals with joint size, up to 94% with multivariate models of the postcranial bones. The best models for the cranium do not exceed 90%. We conclude that postcranial elements are to be preferred to the cranium for estimating sex when the pelvis is unavailable.