The Critical Photographic Variables Contributing to Skull-Face Superimposition Methods to Assist Forensic Identification of Skeletons: A Review.

When an unidentified skeleton is discovered, a video superimposition (VS) of the skull and a facial photograph may be undertaken to assist identification. In the first instance, the method is fundamentally a photographic one, requiring the overlay of two 2D photographic images at transparency for comparison. Presently, mathematical and anatomical techniques used to compare skull/face anatomy dominate superimposition discussions, however, little attention has been paid to the equally fundamental photographic prerequisites that underpin these methods. This predisposes error, as the optical parameters of the two comparison photographs are (presently) rarely matched prior to, or for, comparison. In this paper, we: (1) review the basic but critical photographic prerequisites that apply to VS; (2) propose a replacement for the current anatomy-centric searches for the correct 'skull pose' with a photographic-centric camera vantage point search; and (3) demarcate superimposition as a clear two-stage phased procedure that depends first on photographic parameter matching, as a prerequisite to undertaking any anatomical comparison(s).

Global facial soft tissue thicknesses for craniofacial identification (2023): a review of 140 years of data since Welcker's first study.

This year (2023) marks 140 years since the first publication of a facial soft tissue thickness (FSTT) study. Since 1883, a total of 139 studies have been published, collectively tallying > 220,000 tissue thickness measurements of > 19,500 adults. In just the last 5-years, 33 FSTT studies have been conducted. Herein, we add these data (plus an additional 20 studies) to the 2018 T-Table to provide an update of > 81,000 new datapoints to the global tallied facial soft tissue depths table. In contrast to the original 2008 T-Table, some notable changes are as follows: increased FSTTs by 3 mm at infra second molar (ecm2-iM2'), 2.5 mm at gonion (go-go'), 2 mm at mid-ramus (mr-mr'), and 1.5 mm at zygion (zy-zy'). Rolling grand means indicate that stable values have been attained for all nine median FSTT landmarks, while six out of nine bilateral landmarks continue to show ongoing fluctuations, indicating further data collection at these landmarks holds value. When used as point estimators for individuals with known values across 24 landmarks (i.e., C-Table data), the updated grand means produce slightly less estimation error than the 2018 T-Table means (3.5 mm versus 3.6 mm, respectively). Future efforts to produce less noisy datasets (i.e., reduce measurement and sampling errors as much as possible between studies) would be useful.

Cervicothoracic junction in disaster victim identification: Idiosyncrasies and relevance of body position for advanced chest radiograph comparisons.

Standard plain film medical radiographs often form a valuable line of evidence to identify individuals in large-scale fatality events. While commonly available, chest radiographs present a challenge that their analysis is somewhat more involved and complex than radiographic records of other body regions. For example, chest radiographs concern subtler morphological varieties of smaller anatomical features across a larger number of skeletal elements in contrast to frontal sinus comparisons that concern a large, (often) single, highly variable void within one bone. This does not detract from or discount chest radiographs as useful identification aids, but it does demand additional prerequisite skills in radiographic interpretation to ensure valid conclusions are attained. When subjects deviate from standardized antemortem (AM) radiographic positions and/or the image quality decreases, the complexity of a chest radiograph comparison is elevated. Generally, the current body of forensic radiographic comparison literature infrequently addresses these more complex circumstances. In this paper, we use real-world radiographic comparison reference images from a military DVI repatriation context to illustrate these factors and outline some procedures that enable these complexities to be easily recognized and appropriately addressed at case examination. A report for an exemplar case that concurrently highlights multiple factors is presented. For novices learning radiographic comparison methods, this case review saliently demonstrates: (1) why the AM reference radiograph(s) drive(s) the radiographic comparison procedure; (2) why care should be taken for correct positioning of the cervicothoracic junction in postmortem radiography of chest elements.

Focus distance estimation from photographed faces: a test of PerspectiveX using 1709 frontal and profile photographs from DSLR and smartphone cameras.

As focus distance (FD) sets perspective, it is an important consideration for the forensic analysis of faces in photographs, including those used for craniofacial superimposition. In the craniofacial superimposition domain, the PerspectiveX algorithm has been suggested for FD estimation. This algorithm uses a mean value of palpebral fissure length, as a scale, to estimate the FD. So far, PerspectiveX has not been validated for profile view photographs or for photographs taken with smartphones. This study tests PerspectiveX in both front and profile views, using multiple DSLR cameras, lenses and smartphones. In total, 1709 frontal and 1709 profile photographs of 10 adult participants were tested at 15 ground truth FDs using three DSLR cameras with 12 camera/lens combinations, five smartphone back cameras and four smartphone front cameras. Across all distances, PerspectiveX performed with a mean absolute error (MAE) of 11% and 12% for DSLR photographs in frontal and profile views, respectively, while errors doubled for frontal and profile photographs from smartphones (26% and 27%, respectively). This reverifies FD estimation for frontal DSLR photographs, validates FD estimates from profile view DSLR photographs and shows that FD estimation is currently inaccurate for smartphones. Until such time that FD estimations for facial photographs taken using smartphones improves, DSLR or 35 mm film images should continue to be sought for craniofacial superimpositions.

Perspective distortion tolerances and skull-face registration in craniofacial superimposition: an analytical review.

Craniofacial superimposition requires the photographic registration of a skull at transparency to a photograph of an antemortem (AM) face so that anatomical concordance between the two can be assessed. When the camera vantage point of the AM photograph is exactly replicated for skull photography, the superimposition is a relatively straightforward process as the images are precisely comparable without complicating factors. In practice, however, focus distances are almost never exactly replicated because the focus distance for AM face photography is rarely known. Embedded differences in perspective, thereby, drive the images away from correspondence, raising questions as to how much difference can be tolerated and what image registration methods should be used. Recently, a ± 1% mismatch in facial height has been posited as an acceptable upper tolerance limit to differential perspective, but this proposition is speculative and has not yet been confirmed by tests on real-life images. In addition, the impact of image registration methods, though critically relevant, has received comparatively little consideration. This paper provides the first in-depth review of these intertwined perspective/registration matters and objective evaluation of tolerances by using real 2D photographic images and synthetic images generated from 3D CT data to demonstrate perspective impact on skull morphology. Taken together, the review confirms a ≤ 1% perspective difference in facial height to be a suitable criterion for craniofacial superimposition (at least as a starting point for method improvement), and that image registration should be point-based using a sellion/nasion combination to minimize anatomical misalignment in the principal region-of-interest (the mid-face).

Craniofacial superimposition: a review of focus distance estimation methods and an extension to profile view photographs.

Craniofacial superimposition concerns the photographic overlay of skulls and faces, for skeletal identification. As a phased method that depends on photographic optics first and anatomical comparisons second, superimposition is strongly underpinned by the physics of light travel through glass lenses. So that the downstream (and dependent) anatomical evaluations are not thwarted or erroneous identification decisions risked, it is critical that the optical prerequisites for valid image comparisons are met. As focus distance sets the perspective, the focus distance used for skull photography must be matched to that used at face photography, so that anatomically comparable 1:1 images are obtained. In this paper, we review the pertinent camera optics that set these nonnegotiable fundamentals and review a recently proposed method for focus distance estimation. We go beyond the original method descriptions to explain the mathematical justification for the PerspectiveX algorithm and provide an extension to profile images. This enables the first scientifically grounded use of profile view (or partial profile view) photographs in craniofacial superimposition. Proof of concept is provided by multiple worked examples of the focus distance estimation for frontal and profile view images of three of the authors at known focus distances. This innovation (1) removes longstanding trial-and-error components of present-day superimposition methods, (2) provides the first systematic and complete optical basis for image comparison in craniofacial superimposition, and (3) will enable anatomical comparison standards to be established from a valid grassroots basis where complexities of camera vantage point are removed as interfering factors.

Infracranial radiographic comparison for human identification: A study of image quality and tissue shielding effects.

In this study, we explore how image resolution and tissue shielding can impact correct classification rates (CCRs) of infracranial radiographic comparisons undertaken using small field-of-view radiographs. Thirty-six identification arrays (using clavicles and seventh cervical vertebra) were constructed with each array comprised of five radiographs: one X-ray of a single dry bone (postmortem [PM] skeletal image) and four simulated antemortem [AM] radiographs (radiographs taken pre-skeletization). One AM radiograph in each array represented the ground truth match to the PM radiograph (=25% rate of randomly selecting the correct match). Radiographs were digitally manipulated, so that four varieties of decreasing blur (Gaussian blur = 12-0 pr across 24 arrays), and, for PM clavicles, four varieties of decreasing hard tissue shielding (opacity of 40-0% across 12 arrays) existed. Arrays were evaluated, for their correct PM/AM pair, by 8 anthropologists trained in chest radiograph comparison (CXR; either currently or formerly competency certified by the Defense POW/MIA Accounting Agency CXR training program), 28 current American Board of Forensic Anthropology (ABFA) diplomates and 30 novices. Analysts' CCRs substantially improved when Gaussian blur was <10 pr (55% CCR at >10 pr vs. 89% for <10 pr). Tissue shielding effects increased CCRs on average by +10% for each -10% opacity step (between 40-0% opacity). The CXR anthropologists were the most tolerant of the more challenging identification contexts (highest blur and opacity), reconfirming that analyst training and expertise is an important factor, especially when poorer quality radiographic images are the subject of analysis.

Infra-cranial radiographic comparison for human identification: A study of analyst expertise.

Radiographic comparison for identification is widely utilized. However, these methods are qualitative and subject to analyst ability to correctly read and interpret radiographs. With regards to infra-cranial radiographs, few studies have been conducted to explore the role of practitioner expertize on correct classification rates (CCRs). Here, we undertake two such studies using forensic anthropologists [American Board of Forensic Anthropology (ABFA) certified, practicing but not board-certified anthropologists, and chest radiograph comparison (CXR) anthropologists trained via the Defense POW/MIA Accounting Agency CXR competency training program] and compare their results to novices. To ensure participants only referred to the same skeletal morphology, we cropped radiographs to single bones. An array of four simulated antemortem radiographs was presented to each assessor with each postmortem radiograph. Assessors evaluated arrays for a correct match, which was always present, yielding a 25% rate for random correct selections. Study 1 used anteroposterior C7, posteroanterior second metacarpal, and lateral calcaneus radiographs (three arrays each for nine arrays total), which yielded 86, 81, 69, and 68% mean CCRs for CXR experts, ABFA anthropologists, non-ABFA anthropologists and novices, respectively. Study 2 used anteroposterior C7 and left clavicles (three arrays each for six arrays total), yielding mean CCRs of 100, 96, and 84% for CXR experts, ABFA anthropologists and novices, respectively. As reflected by the CCRs, expertise is clearly a factor for radiographic comparisons, evident not just between novices and anthropologists, but also between anthropologists. We recommend all radiographic comparison analysts be subject to competency/proficiency tests prior to their engagement for forensic casework.

The Dubious Practice of Sensationalizing Anatomical Dissection (and Death) in the Humanities Literature.

Past anatomical dissection practice has received recent attention in the humanities and social science literature, especially in a number of popular format books. In these works, past ethically dubious dissection practices (mostly from the 1700 to 1800s, though they had their origins much earlier on) are again revisited, including stealing the dead for dissection. There are extremely simple, yet very important, lessons to be had in these analyses, including: do not exploit the dead and treat the dead with dignity, respect, and reverence. In this paper, we highlight that these principles apply not just to anatomists but to all parties concerned with bodies for dissection, including journalists and authors from the humanities writing on anatomical dissection whether in the historical or modern-day context. Not too infrequently these same authors/publishers resort to sensationalist language in titles, text, and/or promotion blurbs in a bid to grab attention and sell books. These actions, yet again, exploit dissection subjects for commercial purposes. The use of insensitive and sensationalist language that is designed to shock, fails to set good precedent for young impressionable students and paints an entirely backward picture of modern-day anatomy for intending or existing donors and their families. We suggest that all who participate in anatomical endeavours should strive to do so with reverence toward the dead, including armchair journalists and humanities authors who, just like their hands-on anatomical colleagues, should employ dignified, sensitive, and respectful language that is not sensationalist.

Next-generation osteometric sorting: Using 3D shape, elliptical Fourier analysis, and Hausdorff distance to optimize osteological pair-matching.

Determining which bilateral bones belong to the same person based on shape and size similarity is called pair-matching and it is instrumental for sorting commingled skeletons. To date, pair-matching has popularly been accomplished by visual inspection and/or linear caliper measurements; however, attention is turning increasingly to computational analysis. In this paper, we investigate a fast three-dimensional (3D) computerized shape-analysis method for whole-bone pair-matching using a test sample of 14 individuals (23 femora, 26 humeri, and 26 tibiae). Specifically, the method aims to find bilateral pairs using, as the shape signature criterion, a single 3D outline that snakes around each bone's perimeter as described by a 3D elliptical Fourier analysis function. This permits substantial 3D-point-cloud data reduction, that is, to 0.02% of the starting c.500,000 point cloud or just 100 points, while preserving key 3D shape information. The mean Hausdorff distance (Hd) was applied to measure the distance between each mirrored right-side outline to every left-side outline in pairwise fashion (132, 168 and 169 comparisons, respectively). Both thresholds and lowest Hd were investigated as pair-match criteria, with the lowest Hd producing the best performance results for searches jointly utilizing right-left and left-right directions for comparison: true positive rates of 1.00 (10/10), 1.00 (12/12), and 0.92 (11/12) for the femora, humeri, and tibiae, respectively. The computational time to calculate 469 pairwise 3D comparisons on a single stock-standard Intel® Core™ i7-4650U CPU @ 1.70 GHz was 5 s. This short data processing time makes the method viable for real-world application.

B-mode Ultrasound Measurement of Facial Soft Tissue Thickness for Craniofacial Identification: A Standardized Approach.

Facial soft tissue thicknesses (FSTT) have long formed a quantitative cornerstone of craniofacial identification methods. Measurement approaches could, however, be improved by standardization that enhances the utility/comparability of these FSTT data between studies and authors. This applies equally within the broad classes of measurement techniques, just as it does between them, where many different varieties of tools, tool settings, and practitioner techniques are used within each measurement modality. Although B-mode ultrasound is popularly used and holds some prime advantages, such as the measurement of upright living subjects, technical recommendations that provide basic underlying data structure and standardization are essentially nonexistent. This paper provides the first systematic and illustrated description of a standardized B-mode ultrasound measurement method designed to maximize data utility for craniofacial identification purposes.

An overview of the latest developments in facial imaging.

Facial imaging is a term used to describe methods that use facial images to assist or facilitate human identification. This pertains to two craniofacial identification procedures that use skulls and faces-facial approximation and photographic superimposition-as well as face-only methods for age progression/regression, the construction of facial graphics from eyewitness memory (including composites and artistic sketches), facial depiction, face mapping and newly emerging methods of molecular photofitting. Given the breadth of these facial imaging techniques, it is not surprising that a broad array of subject-matter experts participate in and/or contribute to the formulation and implementation of these methods (including forensic odontologists, forensic artists, police officers, electrical engineers, anatomists, geneticists, medical image specialists, psychologists, computer graphic programmers and software developers). As they are concerned with the physical characteristics of humans, each of these facial imaging areas also falls in the domain of physical anthropology, although not all of them have been traditionally regarded as such. This too offers useful opportunities to adapt established methods in one domain to others more traditionally held to be disciplines within physical anthropology (e.g. facial approximation, craniofacial superimposition and face photo-comparison). It is important to note that most facial imaging methods are not currently used for identification but serve to assist authorities in narrowing or directing investigations such that other, more potent, methods of identification can be used (e.g. DNA). Few, if any, facial imaging approaches can be considered honed end-stage scientific methods, with major opportunities for physical anthropologists to make meaningful contributions. Some facial imaging methods have considerably stronger scientific underpinnings than others (e.g. facial approximation versus face mapping), some currently lie entirely within the artistic sphere (facial depiction), and yet others are so aspirational that realistic capacity to obtain their aims has strongly been questioned despite highly advanced technical approaches (molecular photofitting). All this makes for a broad-ranging, dynamic and energetic field that is in a constant state of flux. This manuscript provides a theoretical snapshot of the purposes of these methods, the state of science as it pertains to them, and their latest research developments.

Clinical Examination of the Extensor Pollicis Brevis: Anatomical Study and Description of a Novel Clinical Sign.

BACKGROUND: The Extensor Pollicis Brevis (EPB) is an extrinsic thumb muscle whose main function is extension of the first metacarpophalangeal joint (MCPJ). It is subject to significant anatomical variation and may be absent, vestigial or have an anomalous distal attachment. Clinical examination of EPB is notoriously difficult and no reliable test has yet been described. We propose a novel test for the accurate examination of EPB. We sought to clarify the anatomical variations of EPB and to validate our clinical test using human cadaveric anatomical tests. METHODS: A structured literature review of all human cadaveric anatomical studies describing the attachments of EPB was performed using MEDLINE and Embase with the key words "Extensor Pollicis Brevis". A cadaveric anatomical study was performed using 18 unembalmed upper limbs. Positive and negative tests were simulated by manipulating the tendons of EPB, Extensor Pollicis Longus (EPL) and Flexor Pollicis Longus (FPL). Changes in tendon tension and joint position were measured and recorded. The EPB anatomy was then determined by dissection. RESULTS: Anatomical variations were present in the majority of wrists, with only 35% of EPB tendons having a distal attachment to the proximal phalanx alone. EPB was absent in 5% of specimens. There was a significant difference between the change in MCPJ position between a positive (36 degrees; 95% CI 25 to 47 degrees) and negative (19 degrees; 95% CI 14 to 25 degrees) clinical test (p = 0.002). CONCLUSIONS: The functional importance of EPB depends on its congenital architecture in addition to the functional demands of the patient. We report a novel clinical test which is effective in demonstrating the integrity of the EPB. A positive test result is observed when a change in MCPJ position that occurs while the interphalangeal joint is brought into flexion from full thumb extension is 25 degrees or more.

The utility of elliptical Fourier analysis for estimating ancestry and sex from lateral skull photographs.

Current quantitative methods for estimating ancestry and sex from skulls typically require substantial manual data collection and specialized recording equipment, which can limit analysis to the laboratory. This limitation could be addressed by establishing a faster, more user-friendly, and automatic data protocol as investigated in the current study using elliptical Fourier analysis (EFA). Ancestry and sex were estimated using outlines acquired from standardized photographs of the skull in norma lateralis (left side). In this investigation, training samples comprised anatomical specimens from five collections: the Hamann-Todd Human Osteological Collection, WM Bass Donated Skeletal Collection, Robert J. Terry Anatomical Skeletal Collection, Khon Kaen Osteological Collection, and Chiba Bone Collection. Groups were defined as Black American female (n=87), Black American male (n=109), Japanese male (n=59), Thai female (n=39), Thai male (n=47), White American female (n=97), and White American male (n=134). EFA was conducted on partial Procrustes-aligned skull outline coordinates, before extracting principal components and using linear discriminant analysis for group assignment. Classification accuracy was determined using the 5-fold cross-validation protocol. Ancestry and sex were classified correctly 73% of the time when all seven reference samples were used. When only Black and White Americans were retained in the reference sample with sex pooled, they were correctly classified 94% of the time. Accuracy of out-of-group ancestry and sex estimation was evaluated using nine White American males from the Defense POW/MIA Accounting Agency Laboratory. A seven-way comparison with all reference samples for estimating both ancestry and sex achieved 89% (8/9) correct classifications, with one misclassification as White American female. These out-of-group results, along with initial training group accuracies, indicate that lateral skull outlines can be used to successfully estimate ancestry and sex with similar accuracy to other methods, and set the basis for future cross-validation testing. Further, the reliance on a single easy-to-take photograph and user-friendly open-source R script facilitates easy application and field use. The protocol is freely available from CRANIOFACIALidentification.com as the SkullProfiler script.

Changes in face topography from supine-to-upright position-And soft tissue correction values for craniofacial identification.

Soft tissues of the human face hang from the skull under the downward vector of gravity. Subsequently, the fall of the tissues is not likely the same between supine, prone or upright positions with ramifications for soft tissue measurements such as average soft tissue thicknesses used in craniofacial identification. Here we use high-resolution Dimensional Imaging® DI3D stereo-photographs (Glasgow, Scotland) to map the shape change between upright and supine position in the same 62 participants and encode the surface shell differences as greyscale pixel intensity values. Statistical tests were conducted using MANOVA at 31 capulometric landmarks, with posture as the independent factor in a repeated measures design, and sex, somatotype and age (two groups of <50 and>50 years) as independent factors in a between subjects design. Results indicate that facial morphology changed in characteristic fashion between the positions: when supine, the soft tissue extruded inferior and lateral to the eyes (Δmin=+1.2mm; Δmax=+3.0mm, p<0.05) and retracted lateral to the mouth and around the nasolabial fold (Δmin=-1.0mm; Δmax=-2.4mm, p<0.05). These patterns were more marked in older subjects (posture=p<0.01, η2=0.55; and age=p<0.01; η2=0.29). By calculating mean heat maps for the faces, this study clearly demonstrates that posture influences the cheeks/eyes as well as the nasolabial fold, thereby holding broader ramifications for face morphology than previously reported. Since many prior facial soft tissue thickness studies report data for supine subjects, correction factors are provided for converting supine facial soft tissue thickness data to upright estimates. Out-of-sample performance tests of posture-corrected supine means derived from two CT samples (using upright B-mode ultrasound data from living subjects as ground truths) confirmed the utility of the correction factors for landmarks that fall in zones affected most by the posture change (lower standard errors after correction). The standard error improvements were -0.9, -0.6, -0.5, and -1.4mm respectively for the mio-mio', go-go', zy-zy' and mr-mr' landmarks (reductions indicated by the negative sign).

TDStats-A fast standardized capability for facial soft tissue thickness analysis in R.

The popular and repeated calculation of facial soft tissue thickness in different samples by different practitioners makes the development of a free, standard, and open-source tool that calculates all necessary statistics in an automated fashion useful. This tool should enable data analysis for single or multiple studies in both independent study-specific format and as a pooled aggregate. The tool should be fast, should facilitate exploratory data analysis, and should provide robust central tendency statistics (shorth and shormaxes). The tool should facilitate effortless analysis, so that once the raw data are entered, little additional input is required of the analyst to maximize user-friendliness. This paper describes in detail such a capability (TDStats v2017.1) specifically formulated for soft tissue thickness analyses and demonstrates its utility by analysing 14,201 publically available data points at 24 landmarks from 1086 subjects in under 45s. Outputs include 120 plots, 15 tables, and 5 summary pdfs. A step-by-step user guide to TDStats is provided as well as additional comments and clarity on the utility of robust central tendency statistics.

Error measurement in craniometrics: The comparative performance of four popular assessment methods using 2000 simulated cranial length datasets (g-op).

For measurements to be accurate and precise, measurement errors should be small. In the anthropometry and craniofacial identification literature, four methods are commonly used for assessing measurement error: Pearson's product moment correlation coefficient (r), intra-class correlation coefficients (ICC), statistical significance tests (often reported by P-values) and the technical error of measurement (TEM; also known as Dalberg's error/ratio). In this paper, the performance of all four of these statistics were evaluated using maximum cranial lengths (g-op) from Howells (n=2524), by duplicating the dataset and mathematically adding known degrees of error to the second set. This was repeated under a broad array of trials (2000 total) each with slightly different amounts of error simulation to comprehensively assess the four error metrics in terms of descriptive power and utility, using the same data for each of the four error assessment methods. Data simulations included the addition of random and systematic errors of different sizes with absolute differences ranging from 1 to 50mm (or in relative terms, 28% of the original measurement). Two sample sizes (n=25 and 2524 individuals) were explored and all analyses were conducted in R. P-values from Student's t-tests only showed significant differences (P<0.05) for the larger sample size when the error was systematic. Small samples, and/or any with random error, did not yield low or significant P-values (P<0.05). When raw differences were <4mm for 95% of the sample (n=2524), the ICC and r were high (>0.97) and remained so even after tripling the error, such that 95% of the sample possessed raw differences up to 12mm (r=0.8). In contrast, the TEM was low initially (<2mm or r-TEM<1%), and then increased (<4.5mm and 2.5%, TEM and r-TEM respectively). These data show that P-values, ICC and r values hold substantial limits for error description as they do not always flag error well. In contrast, TEM appears to covary with error more saliently and holds the advantage that changes are reported in the units of the original measurement. For these reasons, TEM is recommended in favour to P-values, ICC and r.

Facial soft tissue thickness (FSTT) estimation models-And the strength of correlations between craniometric dimensions and FSTTs.

It has been speculated that craniometric dimensions can be used to improve estimations of facial soft tissue thickness (FSTT) in craniofacial identification. Subsequently, linear regression (LR) models have been published, but the practical utility of these models (lower errors than means) has never been tested/demonstrated. Using 71 living subjects measured by B-mode ultrasound, this study calculates and compares standard errors for previously published LR models and untrimmed FSTT means. Correlations between craniometric dimensions and FSTTs were calculated and regression model reproducibility examined by: generating new models using a 61 subject training set; and three-fold cross validation. Published regression models, applied to the above mentioned new individuals of this study, provided substantially worse estimates of ground truth FSTTs than untrimmed arithmetic means (mean Sest=4.0mm compared to 2.8mm, n=61-71). Correlations between craniometrics and FSTTs were generally small (mean of absolute values=0.17, raw interval=-0.24 to 0.48) and only two of 15 previously published LR models were reproducible (mr-mr' and g-g')-i.e., contained the same independent variable with no more than one other different independent variable entering the model. Under three-fold cross-validation (training sets of 40-41 individuals), no LR equation was reproduced across all three validation test runs. Basic craniometric dimensions do not appear to generally improve FSTT estimations and relationships between craniometric dimensions and FSTTs are much weaker and less reliable than previously thought. B-mode ultrasound data for adult Australians were pooled herein to provide larger sampled and updated FSTT statistics for this cohort (n=118-123).