Current practices by forensic anthropologists in adult skeletal age estimation

When determining an age estimate from adult skeletal remains, forensic anthropologists face a series of methodological choices. These decisions, such as which skeletal region to evaluate, which methods to apply, what statistical information to use, and how to combine information from multiple methods, ultimately impacts the final reported age estimate. In this study, a questionnaire was administered to 145 forensic anthropologists, documenting current trends in adult age at death estimation procedures used throughout the field. Results indicate that the Suchey-Brooks pubic symphysis method (1990) remains the most highly favored aging technique, with cranial sutures and dental wear being the least preferred, regardless of experience. The majority of respondents stated that they vary their skeletal age estimate process case-by-case and ultimately present to officials both a narrow and broad possible age range. Overall, respondents displayed a very high degree of variation in how they generate their age estimates, and indicated that experience and expertise play a large role in skeletal age estimates.     

Analysis of age-at-death estimation through the use of pubic symphyseal data

The question of whether age parameters derived from an American population will reliably estimate age-at-death for East European skeletal populations is important since the ability to accurately estimate an individual's age-at-death hinges on what standard is used. A reference sample of identified individuals with known ages-at-death from the regions of the Former Yugoslavia (n = 861) is used to determine the age structure of victims and serves as the prior in the Bayesian analysis. Pubic symphyseal data in the manners of Todd (Am J Phys Anthropol, 3 [1920], 285; Am J Phys Anthropol, 4 [1921], 1) and Suchey-Brooks (Am J Phys Anthropol, 80 [1986], 167) were collected for n = 296 Balkan males and females and for n = 2078 American males and females. An analysis of deviance is calculated using an improvement chi-square to test for population variation in the aging processes of American and East European populations using proportional odds probit regression. When males and females are treated separately, there is a significant association among females and the population (df = 1, chi-square likelihood ratio = 15.071, p = 0.001). New age estimates for Balkan populations are provided and are based on the calculated age distribution from the Gompertz-Makeham hazard analysis and the ages-of-transition. To estimate the age-at-death for an individual, the highest posterior density regions for each symphyseal phase are provided.     

Evaluation of the Suchey-Brooks method for aging skeletons in the Balkans

This study has been carried out to examine whether the Suchey-Brooks (S&B) methods could be successfully applied in age assessment of populations from the Balkans. The known-age sample consists of 33 females and 52 males pairs of pubic bones collected from the autopsy cases. Age estimation by S&B method showed an accuracy of 89.74% in males and 72.0% in females. Statistical analysis showed a positive correlation between the actual age of the investigated individuals and age phases obtained by the S&B method, although the mean values of the sixth age category differed significantly compared with the original model. The most reliable indicators in both sexes were the relief of the symphyseal surface, lipping, symphyseal rim, and dorsal margin. The discriminating power of these indicators was the least reliable in distinguishing S&B phases 2 and 3. Based on these results, the appropriate recommendations for aging Serbian populations are made. There was a good agreement between two observers (kappa=0.726).     

A Bayesian approach to estimate skeletal age-at-death utilizing dental wear

In the forensic context, teeth are often recovered in mass disasters, armed conflicts, and mass graves associated with human rights violations. Therefore, for victim identification, techniques utilizing the dentition to estimate the first parameters of identity (e.g., age) can be critical. This analysis was undertaken to apply a Bayesian statistical method, transition analysis, based on the Gompertz-Makeham (GM) hazard model, to estimate individual ages-at-death for Balkan populations utilizing dental wear. Dental wear phases were scored following Smith's eight-phase ordinal scoring method and chart. To estimate age, probability density functions for the posterior distributions of age for each tooth phase are calculated. Transition analysis was utilized to generate a mean age-of-transition from one dental wear phase to the next. The age estimates are based on the calculated age distribution from the GM hazard analysis and the ages-of-transition. To estimate the age-at-death for an individual, the highest posterior density region for each phase is calculated. By using a Bayesian statistical approach to estimate age, the population's age distribution is taken into account. Therefore, the age estimates are reliable for the Balkan populations, regardless of population or sex differences. The results showed that a vast amount of interpersonal variation in dental wear exists within the current sample and that this method may be most useful for classifying unknown individuals into broad age cohorts rather than small age ranges.     

Age estimation from the human os coxa: a test on a documented Italian collection*

Current standards for age at death estimation from the pelvis are based on Americans of European and African ancestry. Our limited understanding of population variability hampers our efforts to apply these techniques to the various skeletal populations around the world, especially in global forensic contexts. However, documented skeletal samples are rare, limiting our ability to test our techniques. This study tested the Suchey-Brooks pubic symphysis aging method and the auricular surface method originally developed by Lovejoy et al. on a large sample (n = 404) of known sex and age from the Sassari Collection, housed at the Museum of Anthropology at the University of Bologna, Italy. The results indicate that for both methods, bias and inaccuracy increased with age and actual age tended to be underestimated over the age of 40. The auricular surface method performed slightly better, exhibiting slightly lower levels of bias and inaccuracy, especially for males.     

A Test of Hartnett's Revisions to the Pubic Symphysis and Fourth Rib Methods on a Modern Sample

Estimating age at death is one of the most important aspects of creating a biological profile. Most adult age estimation methods were developed on North American skeletal collections from the early to mid‐20th century, and their applicability to modern populations has been questioned. In 2010, Hartnett used a modern skeletal collection from the Maricopia County Forensic Science Centre to revise the Suchey‐Brooks pubic symphysis method and the ??can et al. fourth rib methods. The current study tests Hartnett's revised methods as well as the original Suchey‐Brooks and ??can et al. methods on a modern sample from the William Bass Skeletal Collection (N = 313, mean age = 58.5, range 19–92). Results show that the Suchey‐Brooks and ??can et al. methods assign individuals to the correct phase 70.8% and 57.5% of the time compared with Hartnett's revised methods at 58.1% and 29.7%, respectively, with correctness scores based on one standard deviation of the mean rather than the entire age range. Accuracy and bias scores are significantly improved for Hartnett's revised pubic symphysis method and marginally better for Hartnett's revised fourth rib method, suggesting that the revised mean ages at death of Hartnett's phases better reflect this modern population. Overall, both Hartnett's revised methods are reliable age estimation methods. For the pubic symphysis, there are significant improvements in accuracy and bias scores, especially for older individuals; however, for the fourth rib, the results are comparable to the original ??can et al. methods, with some improvement for older individuals.     

Application of the Suchey-Brooks method to three-dimensional imaging of the pubic symphysis

Age determination is a major field of interest in forensic anthropology. Among the different methods based on macroscopic skeletal study, the Suchey-Brooks method, which analyzes the pubic symphysis, is one of the most reliable. We applied the Suchey-Brooks method to three-dimensional computed tomographic reconstructions of the pubic symphysis. We demonstrated excellent agreement between the results of analysis of bone samples and those of the three-dimensional images, in particular regarding ridges of the articular surface and delimitation of the extremities. The accuracy of age estimation did not significantly differ (Wilcoxon test) between the Suchey-Brooks method applied to bones and the same method applied to CT images. Using high-quality images, this approach seems as reliable as the standard Suchey-Brooks method and offers several advantages: no bone preparation, no damage to bone material, and the possibility of application to living individuals.     

Evaluation of cast methods for estimating age from the os pubis.

Age-related changes of the pubic symphysis have gained wide acceptance among physical anthropologists as one basis for estimating adult skeletal age. However, these methods have not been tested by independent observers on large samples with known ages at death that represent contemporary populations. In this study 202 female and 116 male pairs of pubes collected at autopsy were blindly evaluated for age using the McKern-Stewart or Gilbert-McKern and Suchey-Brooks methods. Performance of the methods was measured by mean absolute deviation of true age from scored interval means and frequencies of true age falling within +/- 1 and +/- 2 standard deviations from the mean. The results suggest that the Suchey-Brooks methods are superior in forensic applications and that the racially specific refinement for males should be used. Age estimates should include +/- 2 standard deviations, and chances of error should be considered, especially when advanced age or debilitation is suspected.     

Determination of male age at death in Chinese Han population: using quantitative variables statistical analysis from pubic bones

Determination of age at death by skeletal features is difficult, but important, both in forensic and physical anthropology. Pubic symphysis is a widely accepted morphological indicator, which provides the best result for personal age identification. Age prediction in this study used nine indicators of morphological changes, viz: ridges and furrows on the symphysial surface, ridge of pubic tubercle, lower extremity, ventral beveling, ossific nodules, dorsal margin, ventral rampart, general macroscopic changes of symphysial surface, and bone density of the symphysial surface. Samples were drawn from 262 male individuals. The study procedures are as follows: Firstly, we examined the morphological features of pubic symphysis using criteria similar to Hanihara's and Suchey-Brooks (SB). Secondly, we evaluated each stage with an appropriate score. Thirdly, we deduced four equations of male age assessment of morphological features by statistic analysis. The results were compared with Hanihara's and Suchey-Brooks method; the similarities and differences among them were discussed objectively. The method produced consistent results as well as developing the criteria of Hanihara's and Suchey-Brooks'.     

Modeling Bone Surface Morphology: A Fully Quantitative Method for Age‐at‐Death Estimation Using the Pubic Symphysis

The pubic symphysis is widely used in age estimation for the adult skeleton. Standard practice requires the visual comparison of surface morphology against criteria representing predefined phases and the estimation of case‐specific age from an age range associated with the chosen phase. Known problems of method and observer error necessitate alternative tools to quantify age‐related change in pubic morphology. This paper presents an objective, fully quantitative method for estimating age‐at‐death from the skeleton, which exploits a variance‐based score of surface complexity computed from vertices obtained from a scanner sampling the pubic symphysis. For laser scans from 41 modern American male skeletons, this method produces results that are significantly associated with known age‐at‐death (RMSE = 17.15 years). Chronological age is predicted, therefore, equally well, if not, better, with this robust, objective, and fully quantitative method than with prevailing phase‐aging systems. This method contributes to forensic casework by responding to medico‐legal expectations for evidence standards.     

The Utility of the Samworth and Gowland Age‐at‐Death “Look‐up” Tables in Forensic Anthropology*

Abstract: Accurate age‐at‐death estimates are crucial to forensic anthropologists when onstructing biological profiles aimed at narrowing a missing‐persons list and to allow for timely and efficient identification of an unknown victim. The present contribution evaluates the utility of three new age‐at‐death estimation techniques recently proposed by Samworth and Gowland (2007). Results indicate that, in the samples under study, the Samworth and Gowland estimates from the pubic symphysis and auricular surface perform similar to alternate phase methods. The combined method does not appear to further enhance either the precision or the accuracy of the single pubic symphysis age‐at‐death estimate. In conclusion, these new methods seem to be more robust to distribution deviations than originally proposed by Samworth and Gowland (2007). They are therefore suitable for immediate and reliable forensic usage in the United States and worthy of further research for their use in North American forensic contexts.     

A Comparative Assessment of the Chen et al. and Suchey‐Brooks Pubic Aging Methods on a North American Sample, ,

Accurately estimating the age‐at‐death of adult human skeletons is fundamental in forensic anthropology. This study evaluates the accuracy of two pubic bone age estimation methods—Chen et al. and Suchey‐Brooks. Specimens were obtained from a known collection of modern pubic bones curated at the Maricopa County Forensic Science Center in Phoenix, Arizona. A sample of 296 left male pubic bones of European ancestry was statistically evaluated via bias, absolute mean error, and intra‐ and inter‐observer error. Results indicate that the two methods are similar; the Suchey‐Brooks method is the most accurate for aging young adults (error c. 7 years), while the Revised Chen et al. method is most accurate for aging middle‐age adults (error c. 6 years). Thus, the Chen et al. method is an important contribution to forensic anthropology for aging older adult skeletal remains. There are, however, some limitations such as subjectivity and the intricate scoring system of Chen et al. method.     

Forensic Age-at-Death Estimation from the Human Sacrum*

Abstract: A new method is described here that incorporates seven developmental and degenerative changes for estimating chronological age from morphological features of the human sacrum. The construction of this method involved multiple stages of trait identification, character-state definition and age correlation, rank-order phase development, and percent-correct sample testing with phase and sample aggregation, all of which resulted in a six-phase component system for application on modern individuals. This phase system was first developed on European American male and female samples from the Hamann-Todd collection; then tested on African American male and female Hamann-Todd samples as well as European American male and females from the WM Bass collection to examine possible sex and/or ancestry differences. Variation in age estimates due to sex and ancestry was negligible; thus, the multiple samples were all pooled creating a robust method with a large sample size. Overall age ranges increase in width at two standard deviations as is expected from degenerative age-related processes but retain utility in forensic situations.     

A Bayesian Approach to Age‐at‐Death Estimation from Osteoarthritis of the Shoulder in Modern North Americans

Osteoarthritis (OA) is a marker of degeneration within the skeleton, frequently associated with age. This study quantifies the correlation between OA and age‐at‐death and investigates the utility of shoulder OA as a forensic age indicator using a modern North American sample of 206 individuals. Lipping, surface porosity, osteophyte formation, eburnation, and percentage of joint surface affected were recorded on an ordinal scale and summed to create composite scores that were assigned a specific phase. Spearman's correlation indicated a positive relationship between each composite score and age (right shoulder = 0.752; left shoulder = 0.734). Transition analysis revealed a tendency toward earlier degeneration of the right shoulder. Bayesian statistics generated phase‐related age estimates based on highest posterior density regions. Best age estimates were into the seventh decade at the 90th and 50th percentile. The proposed method supplements traditional techniques by providing age estimates beyond a homogenous 50+ age cohort.     

Skeletal estimation and identification in American and East European populations

Forensic science is a fundamental transitional justice issue as it is imperative for providing physical evidence of crimes committed and a framework for interpreting evidence and prosecuting violations to International Humanitarian Law (IHL). The evaluation of evidence presented in IHL trials and the outcomes various rulings by such courts have in regard to the accuracy or validity of methods applied in future investigations is necessary to ensure scientific quality. Accounting for biological and statistical variation in the methods applied across populations and the ways in which such evidence is used in varying judicial systems is important because of the increasing amount of international forensic casework being done globally. Population variation or the perceived effect of such variation on the accuracy and reliability of methods is important as it may alter trial outcomes, and debates about the scientific basis for human variation are now making their way into international courtrooms. Anthropological data on population size (i.e., the minimum number of individuals in a grave), demographic structure (i.e., the age and sex distribution of victims), individual methods applied for identification, and general methods of excavation and trauma analysis have provided key evidence in cases of IHL. More generally, the question of population variation and the applicability of demographic methods for estimating individual and population variables is important for American and International casework in the face of regional population variation, immigrant populations, ethnic diversity, and secular changes. The reliability of various skeletal aging methods has been questioned in trials prosecuted by the International Criminal Tribunal for the Former Yugoslavia (ICTY) in The Prosecutor of the Tribunal against Radislav Krstic (Case No. IT-98-33, Trial Judgment) and again in the currently ongoing trial of The Prosecutor of the Tribunal against Zdravko Tolimir, Radivolje Miletic, Milan Gvero, Vinko Pandurevic, Ljubisa Beara, Vujadin Popovic, Drago Nikolic, Milorad Trbic, Ljubomir Borovcanin (IT-05-88-PT, Second Amended Indictment). Following the trial of General Krstic, a collaborative research project was developed between the Forensic Anthropology Center at The University of Tennessee (UT) and the United Nations, International Criminal Tribunal for the Former Yugoslavia, Office of the Prosecutor (ICTY). The purpose of that collaboration was to investigate methods used for the demographic analysis of forensic evidence and where appropriate to recalibrate methods for individual estimation of age, sex, and stature for specific use in the regions of the former Yugoslavia. The question of "local standards" and challenges to the reliability of current anthropological methods for biological profiling in international trials of IHL, as well as the performance of such methods to meet the evidentiary standards used by international tribunals is investigated. Anthropological methods for estimating demographic parameters are reviewed. An overview of the ICTY-UT collaboration for research aimed at addressing specific legal issues is discussed and sample reliability for Balkan aging research is tested. The methods currently used throughout the Balkans are discussed and estimated demographic parameters obtained through medico-legal death investigations are compared with identified cases. Based on this investigation, recommendations for improving international protocols for evidence collection, presentation, and research are outlined.     

Metric Assessment of the Pubic Bone Using Known and Novel Data Points for Sex Estimation,

Biological sex estimation of skeletal remains is essential in forensic and archaeological analyses. Anthropologists most often use the pelvis, which is the most sexually dimorphic element both morphologically and metrically. While nonmetric pubic bone features have been studied extensively, few metric studies have examined this individual bone for dimorphism. For this study, three observers examined three previously identified and ten novel measurements of the pubic body on a modern sample of isolated pubic bones from the Maricopa County Forensic Science Center (FSC), in Phoenix, Arizona (n = 400). A relationship between pubic body measurements and biological sex was demonstrated, with significant correlations. Discriminant function analyses found that five measurements, four of which were novel, discriminated between males (89%) and females (86%). Observer experience level did not significantly impact the results. These five measurements were reliable and show promise for inclusion in metric methods for assessment of sex.     

Pubic Symphyseal Age Estimation from Three‐Dimensional Reconstructions of Pelvic CT Scans of Live Individuals

Skeletal age estimation using the pubic symphysis is a reliable and popular practice among forensic anthropologists. In instances in which accessing the skeleton is impossible, such as in the case of living individuals, three‐dimensional (3D) reconstructions of computed tomography (CT) scans can be created and analyzed for aspects of the biological profile. This study examined 3D reconstructions of pelvic CT scans of a sample of 44 live adults to estimate age using the Suchey–Brooks J Hum Evol 1990;5(3):227‐38 method. Images were created using OsiriX software (Pixmeo, Geneva, Switzerland). Estimated age ranges based on the 3D‐CT images captured the true age of the individual at the time of the CT scan 79.5% of the time with good intra‐observer reliability. The features best visualized on the 3D images included the ossific nodule and the pubic symphyseal rim. This study shows that clinical CT scanning parameters are adequate for creating 3D images to be analyzed for age using the pubic symphysis.     

Secular Change in Morphological Pelvic Traits used for Sex Estimation

This research evaluates secular change in Phenice's (Am J Phys Anthropol, 30, 1969 and 297) three morphological traits of the pubis, as described by Klales et al. (Am J Phys Anthropol, 149, 2012 and 104): medial aspect of the ischio‐pubic ramus, subpubic contour, and ventral arc. Ordinal scores were collected for these traits and compared between a sample of innominates from the historical Hamann–Todd Collection (n = 170) and modern Bass Donated Collection (n = 129). Using the Freeman–Halton test, significant differences between temporal sample score frequencies were found for all traits in females and for the subpubic contour and ventral arc in males. Despite these findings, classification accuracy using logistic regression between the temporal periods remained low (68.7%). These results suggest that secular changes in trait expression are occurring; however, sex estimation methods using these traits and created with historical samples are still applicable to modern forensic cases. In fact, the secular changes occurring in these traits contribute to better classification accuracy between sexes in modern populations.     

Quantification of Pubic Symphysis Metamorphosis Based on the Analysis of Clinical MDCT Scans in a Contemporary Malaysian Population

Forensic age estimation methods are biased to sex and population; in general, accuracy is reduced when applied to foreign populations. This study assessed the accuracy of the Suchey–Brooks method in contemporary Malaysian individuals and aimed to formulate population‐specific standards. Multi‐detector computed tomography scans of 355 individuals (165 male; 190 female) of 15–83 years of age were reconstructed using 3D‐volumetric rendering in RadiAnt. Pubic symphyseal phase, bias, inaccuracy, and percentage correct age classifications are examined. Transition analysis was used to develop age estimation standards. High observer agreement (κ = 0.763–0.832) and a positive relationship between age and pubic symphyseal phase (r = 0.884–0.90) were demonstrated. Mean inaccuracies were 8.62 and 8.95 years for males and females, respectively; overall correct classification was 97.8%. Transition ages between phases in males were 18.79, 23.29, 28.85, 43.64, and 61.15 years; in females, the corresponding data were 19.77, 22.53, 32.62, 41.85, and 57.39 years.