Experimental sharp force injuries to ribs: Multimodal morphological and geometric morphometric analyses using micro-CT, macro photography and SEM

[Forensic imaging of sharp force injuries]

BACKGROUND

Answering legal questions is everyday routine in forensic medicine. The reconstruction of violent crimes following attacks with sharp and/or pointed instruments is usually complex and can hardly be adequately answered using traditional forensic methods such as autopsies. For this reason, clinical and postmortem radiology has become the ideal complement to forensic medicine.

METHODS

While classic X‑ray is unsuitable to image soft tissue injuries, and magnetic resonance imaging is too expensive, too complex and also not available everywhere, multislice computed tomography (MSCT) has now emerged as the method of choice in forensic imaging for the assessment of the consequences of sharp force injuries.

ACHIEVEMENTS

Forensic imaging, especially MSCT, offers an indispensable addition to reconstruction, particularly after stab wounds. In many cases, it is at least equal to, and in some cases superior to, the classic autopsy in the assessment of stab wounds, the reconstruction of the sequence of events or the assessment of (life-threatening) injuries.

CONCLUSIONS

The forensic radiological assessment after sharp violence requires experience in both the field of radiology and forensic medicine. Provided that both disciplines work closely together, forensic radiology can be an essential tool in the care for victims of violence.

A proposal for cut marks classification using machine learning: Serrated vs. non-serrated, single vs. double-beveled knives

In tool mark identification, there is still a lack of characteristics and methodologies standardization used to analyze and describe sharp force trauma marks on skeletal remains. This study presents a classification method for cut marks on human bones, providing an applicable methodology for their examination and the relevant terminology for describing cases of sharp force trauma. A total of 350 cut marks were produced by stabbing pig ribs (Sus scrofa) with seven knives. The samples were analyzed under a stereomicroscope with a tangential light source. Through the analysis of cut marks, eleven traits were identified as significantly associated with the type of knife used. These traits included the general morphology of the kerf shape, the entrance and exit cross-profile shapes, the location of the rising on the entrance and exit cross-profile, the presence or absence of feathering, the presence or absence of shards and the location and the general morphology of the mounding. Binary logistic regression models were later trained and tested using nine out of the eleven traits. The first model categorized the cut mark as either produced by a serrated or non-serrated blade, while the second, as either produced by a single- or double-beveled blade. Classification scores of those models ranged between 63%-85% for the serration class and 63%-89% for the blade bevel class. This study proposes a new set of traits and the use of machine learning models to standardize and facilitate the analysis of stab wounds.

Recognition of the Presence of Bone Fractures Through Physicochemical Changes in Diagenetic Bone

Much research has focused on attempting to understand the drivers of bone diagenesis. However, this sensitive process is easily influenced by various factors, particularly the condition of the remains (i.e., whether they have been subjected to trauma). Previous research demonstrates that trauma can influence soft tissue decomposition, yet to date, no studies have looked at how bone fractures could affect bone diagenesis. To address this gap, two short timescale studies were conducted to investigate the influence of bone fractures on the physicochemical composition of disarticulated, partially fleshed animal remains. Disarticulated porcine bones were either fractured using blunt force or sharp force whilst fresh (producing perimortem damage), at 60 days producing postmortem damage (postmortem interval (PMI)), or left intact and left outside for up to 180 days post-fracture/240 days PMI. Retrieved bone sections were then analyzed for physicochemical differences using non-destructive methods, i.e., scanning electron microscopy energy dispersive spectroscopy and Fourier transform infrared spectroscopy with attenuated total reflectance. It was hypothesized that differences would be found in the physicochemical composition between the bones with fractures and those without after undergoing diagenetic change. The bone fractures significantly affected the elemental composition of bone over time, but structural composition initially remained stable. It was also possible to distinguish between perimortem and postmortem fractures using these two analytical techniques due to physicochemical differences. This research shows bone fractures can significantly alter the physicochemical composition of the bone during the postmortem period and have the potential to facilitate more accurate PMI estimations in forensic contexts.

Stereomicroscopic analysis of cut marks inflicted by a knife with blade damage

Skeletal cut mark analysis provides relevant information on the general class characteristics of suspect knife. However, there is a lack of research on the influence of blade damage on cut mark analysis. This study aimed to thoroughly investigate the effects of damaged knife blades on cut marks' morphological and morphometrical characteristics. Fifteen undamaged, non-serrated knives were used to cut human ribs to make control cut marks. The knife blades were then damaged by a series of cuts on the bones. A comparison was made between the control cuts and 3 groups of cut marks inflicted by blades that had been damaged to different degrees. The results showed that the damaged blades created wider cut marks than undamaged one. Kerf morphology was likely to imitate the cuts made by the serrated blades such as an elliptical shape, a V-shaped cross-section and the presence of coarse striations. Wear-related features can affect cut mark analysis as the marks left behind by blades damaged to different degrees showed dissimilar dimensions and morphologies. The findings of this study can be applied to a forensic investigation when cut marks were caused by a knife with a damaged blade.

Use of different imaging techniques in stab wound analysis

Stab wound analysis is a relatively new field of study in forensic science, and there is currently much debate regarding the effectiveness of the analysis due to a lack of validation studies. Furthermore, the underlying viewpoints on the success of stab wound analysis vary. Examination of cut marks, for example, can reveal a variety of characteristics which can be used to determine the type of weapon that was used to inflict them. However, published studies are not consistent when identifying knife blade characteristics, instead considering a wide variety of morphological aspects and their potential value in forensic scenarios. The existing research methodology is therefore inadequate to reliably inform in such contexts, and future experimental design should be influenced by the conditional variance in stabbings in order to provide reliable findings. The research presented here takes a systematic approach to the problem, compiling the published literature (up to September 2023) on the use of different imaging methods applied to stab wound examination to create a taxonomy to examine trends in methodological approaches in both research and investigative settings. This approach identified that published studies could be classified as either morphological or morphometrical, and further sub-classified based on their degree of success and the findings reached. This emphasises the importance of prioritising research into mark data, and the need for a multi-technique, multi-disciplinary approach. A decision tree was created to illustrate which mark attributes should be studied for which purpose, and using which imaging method(s). Furthermore, the research presented identifies two key areas in stab wound research which should be the focus of standardisation efforts, namely methodological procedures and mark characteristic collection. Knife markings are difficult to interpret, but further research and standardisation of kerf mark analysis, as highlighted here, will improve the efficiency and reliability of both forensic investigations and future experimental studies.

A probabilistic model for murder weapon identification using stab-marks in human ribs

The aim of this article is to provide a scientific and statistical basis to identify the murder weapon in stabbing cases from the geometric characteristics of the stab-marks left on human ribs. For this purpose, a quantitative predictive model is developed, based on geometric measurements of the stab-mark and its location along the rib. A general method based on Bayesian inference and probabilities is used for the model development, rather than a deterministic model given its inability in certain occasions to identify the murder weapon. Following the process explained in this article to collect the stab-mark information required, the complete probabilistic model exposed attained a high accuracy in the identification of the murder weapon between two macroscopically identical blades with a microscopic alteration in one of them (more than 90% of correct identification is achieved).

Dehydration-Induced alterations to sharp force trauma on Sus domesticus radii

Dehydration is a taphonomic process that affects nearly all skeletal remains, yet there is a dearth of evidence on this process within the forensic taphonomy literature. When considering the forensic implications of skeletal dehydration, a particular area of concern is sharp force trauma due to its global prominence in forensic cases. In an attempt to address these literature gaps and quantify the effects that dehydration has on skeletal elements, a controlled experiment subjected Sus domesticus (i.e., domestic pig) radii samples (n = 36) to laboratory-induced dehydration after they were inflicted with knife trauma. All samples were photographed pre- and post-dehydration; bone section and kerf mark length, width, and area were then measured from these photographs using ImageJ. Statistical analysis of pre- and post-dehydration samples showed that all measurements experienced significant (p ≤ 0.001) shrinkage, with bone sample area shrinking an average of 8.8 % and kerf mark area an average of 29.7 %. Alterations in length, width and area between the kerf marks and bone samples showed a weak, moderate, and strong correlation, respectively. These findings suggest that anthropological analysis may be affected by dehydration-induced shrinkage, highlighting the necessity of continued research into the effects of dehydration on skeletal trauma.

A Novel Approach for the Shape Characterisation of Non-Melanoma Skin Lesions Using Elliptic Fourier Analyses and Clinical Images

The early detection of Non-Melanoma Skin Cancer (NMSC) is crucial to achieve the best treatment outcomes. Shape is considered one of the main parameters taken for the detection of some types of skin cancer such as melanoma. For NMSC, the importance of shape as a visual detection parameter is not well-studied. A dataset of 993 standard camera images containing different types of NMSC and benign skin lesions was analysed. For each image, the lesion boundaries were extracted. After an alignment and scaling, Elliptic Fourier Analysis (EFA) coefficients were calculated for the boundary of each lesion. The asymmetry of lesions was also calculated. Then, multivariate statistics were employed for dimensionality reduction and finally computational learning classification was employed to evaluate the separability of the classes. The separation between malignant and benign samples was successful in most cases. The best-performing approach was the combination of EFA coefficients and asymmetry. The combination of EFA and asymmetry resulted in a balanced accuracy of 0.786 and an Area Under Curve of 0.735. The combination of EFA and asymmetry for lesion classification resulted in notable success rates when distinguishing between benign and malignant lesions. In light of these results, skin lesions’ shape should be integrated as a fundamental part of future detection techniques in clinical screening.

Forensic applications of micro-computed tomography: a systematic review

Purpose

The aim of this systematic review was to provide a comprehensive overview of micro-CT current applications in forensic pathology, anthropology, odontology, and neonatology.

Methods

A bibliographic research on the electronic databases Pubmed and Scopus was conducted in the time frame 01/01/2001–31/12/2021 without any language restrictions and applying the following free-text search strategy: “(micro-computed tomography OR micro-CT) AND (forensic OR legal)”. The following inclusion criteria were used: (A) English language; (B) Application of micro-CT to biological and/or non-biological materials to address at least one forensic issue (e.g., age estimation, identification of post-mortem interval). The papers selected by three independent investigators have been then classified according to the investigated materials.

Results

The bibliographic search provided 651 records, duplicates excluded. After screening for title and/or abstracts, according to criteria A and B, 157 full-text papers were evaluated for eligibility. Ninety-three papers, mostly (64) published between 2017 and 2021, were included; considering that two papers investigated several materials, an overall amount of 99 classifiable items was counted when referring to the materials investigated. It emerged that bones and cartilages (54.55%), followed by teeth (13.13%), were the most frequently analyzed materials. Moreover, micro-CT allowed the collection of structural, qualitative and/or quantitative information also for soft tissues, fetuses, insects, and foreign materials.

Conclusion

Forensic applications of micro-CT progressively increased in the last 5 years with very promising results. According to this evidence, we might expect in the near future a shift of its use from research purposes to clinical forensic cases.

Radiological detection of sharp force skeletal trauma: an evaluation of the sensitivity of Lodox in comparison to CT and X-ray

Victims of violent crime often have evidence of sharp force trauma (SFT) which needs to be examined to accurately investigate these cases. The abilities of CTs, X-rays, and Lodox to detect skeletal SFT defects and the minimum number of impacts were assessed, as were their abilities to macroscopically interpret SFT with the aim of identifying the class of weapon used. Ten pigs were, post-mortem, stabbed using a kitchen knife on one side of the body and chopped using a panga on the other side. They were then scanned and macerated. The number of SFT defects, type of SFT, and minimum number of impacts identifiable osteologically were recorded, as well as when using each imaging modality. CTs were most sensitive for detecting stab and chop defects (56.7% and 78.3%, respectively) and the minimum number of impacts (82.8%), while X-rays were least sensitive (17.2% for stab wounds, 46.5% for chop marks, and 43.5% for impacts). Lodox detected 26.8% of stab defects, 59.3% of chop marks, and 58.4% of impacts. The type of SFT for more than 70.0% of identified defects was correctly classified using all methods, while only Lodox had moderate sensitivities for stab wounds (52.4%). When radiological assessments of skeletal SFT are required, CTs should be performed, but Lodox can be used as an alternative. However, dry bone analyses still produce the best results and should be performed whenever possible. Macroscopic interpretations of skeletal SFT to broadly determine the class of weapon used is possible radiologically.

Perimortem Skeletal Sharp Force Trauma: Detection Reliability on CT Data, Demographics and Anatomical Patterns from a Forensic Dataset

Simple Summary

The increased use of computed tomography images in forensic anthropology is easily explained with a variety of benefits: among other reasons they are digitally stored, they can easily be shared and they are non-invasive. However, it is not clear how suitable these images are for forensic anthropologists to detect sharp force trauma. Therefore, we analyzed computed tomography images, by observing digital images of 41 forensic cases in different viewing modalities. In addition, we looked for anatomical injury patterns in the soft- and hard-tissues and any significant correlations between the manner of death (suicide or homicide) with different parameters. Our findings indicated a superiority of viewing the images in 2D, but not all bone lesions were detected. The manner of death was significantly correlated to some of the parameters, which could be extrapolated to future forensic anthropological cases. We promote the inclusion of imaging training into the anthropological curricula.

Abstract

The increasing importance of trauma analysis by means of postmortem computed tomography (PMCT) is insufficiently reflected in forensic curricula, nor are best practice manuals available. We attempt to detect sharp force bone lesions on PMCT of closed forensic cases with the aims of assessing errors and pointing out patterns in anatomical location and manner of death (MOD). We investigated 41 closed sharp force fatality cases, with available PMCT and forensic reports. Two observers with different radiological training assessed the lesions on PMCT scans (2D and 3D) for comparison with the reports. Between 3% (suicides) and 15.3% (homicides) of sharp force injuries caused visible bone lesions. While our observations were repeatable, each forensic investigation left a similar number of bone lesions undetected. Injury patterns differed between MOD, with thoracic bone lesions being most frequent overall. Soft tissue injury location varied between the MOD. Associations between MOD and age as well as number of injuries were significant. The detection of bone lesions on PMCT for untrained forensic specialists is challenging, curricula and pertinent manuals are desirable. With the low frequency of bone lesions compared to soft tissue injuries, we should be aware when analyzing decomposed bodies.

Variability and specificity of bone cutting mark properties in cases involving stabbing with knives

Sharp force traumas are frequently encountered in stabbing crime victims. During an examination, the properties of cutting marks in bones are compared with the properties of suspect tools, particularly knives. Therefore, the variation and specificity of knife and cutting mark properties must be known. This article provides the variability and specificity of a set of knife blade and cutting mark properties. Plain and serrated knives are used to create experimental cutting marks in porcine ribs, knife properties are derived from surface acquisitions of the blades and mark properties from Micro-CT data. We consider two conditions, automated stabbing using a motorized stage and manual stabbing. In addition, we study the influence of maceration on marks. For knives, the blade edge angle, blade thickness, and bevel height, and for cutting marks, the shape, the wall angle, the width, and the bevel height are determined and compared. The results show that the relationship between corresponding properties of blades and marks depends on the knife type. For plain knives, the width and wall angle of the marks are dependent on the mark depth and are significantly smaller than the blade properties edge angle and width. For serrated knives, this is not the case. The mark shape only provides slight support for a knife type for marks deeper than the blade bevel height. In conclusion, mark properties are only specific for a particular knife brand and model if the blade properties differ significantly and assuming a specific knife type.

Knife cut marks inflicted by different blade types and the changes induced by heat: a dimensional and morphological study

Detailed information on skeletal trauma analysis of burned bone is important to ascertain the manner and cause of death in forensic casework. This research used three different knife types, one with a non-serrated blade, one a fine-serrated blade, and one a coarse-serrated blade, to inflict trauma to manually macerated Sus scrofa ribs (n = 240), and these ribs were later exposed to heat. Qualitative and quantitative analyses were conducted using macroscopic and microscopic techniques to assess specific characteristics of the cut marks. Differences in cut mark dimension and morphology of the ribs were investigated. After heat exposure, the cut marks on the rib samples remained recognisable and did not alter considerably. A level of dimensional and morphological preservation was reliant on the cutting action and the features of the knife blade as well as surrounding bone injury. The cut marks inflicted by the non-serrated blade remained recognisable despite exposure to the burning process. However, the cut marks inflicted by the coarse-serrated blade were likely to change significantly when exposed to heat. This study leads to two important results: (1) identification of pre-existing cut marks prior to heat exposure is possible in reconstructed burned bone fragments, and (2) cut marks from different types of knife blades showed dissimilar responses to heat. The outcomes obtained in this study stressed the need to adopt great care with the effects of heat on skeletal trauma analysis.

The stereomicroscope and scanning electron microscope comparison of false starts bones produced by an oscillating autopsy saw

In forensic anthropology, saw mark analysis plays an important role in cases of criminal dismemberment. Autopsy saw is not used by the perpetrator in cases of dismemberment, but the forensic pathologist may accidentally create false starts with this saw during an autopsy, especially while sampling bones for further analysis, and these autopsy false starts can be confused with false starts produced by the offender. In this study, the characteristics of 20 false starts were compared using stereomicroscopy (SM) and scanning electron microscopy (SEM). These bone false starts were selected at random from a previous study of 100 false starts created by an electrical oscillating autopsy saw on human femoral bones. That study had enabled the categorization of the lesions into two groups ("superficial group" and "deep group") with a 0.52 mm depth cut off, based on the dramatic differences in lesion characteristics between these two groups. In the current study, SEM confirmed the characteristics of the false starts (walls and profile shapes, striae, bone islands and bone debris were studied), and above all explained the mechanism whereby oval bone islands in deep lesions are formed. Bone islands are due to the horizontal and vertical movement of the oscillating autopsy blade.

Technical note: A novel method for gentle and non-destructive removal of flesh from bones

For bone preparation, several maceration techniques are available; however, gentle defleshing and soft tissue removal from bones without damaging the bone surface remains a challenge. The study aims to develop a novel, inexpensive, rapid, and resource-saving maceration technique that does not lead to bone surface changes and allows the study of signs of violence on the bone surface. Pig ribs and femurs were covered in aluminum foil and treated in the oven for 5 h at different temperatures with and without detergent. Additionally, femurs were placed in hot non-boiling water containing household bleach and detergents for 1 h. Examinations using macro photography, stereo and fluorescence microscopy, and micro-computed tomography showed no surface changes after treatment at 100 °C, such as flakes or bone cracks, on the ribs. The femurs showed surface changes after incubation in water, such as roughening.

Obtaining new resolutions in carnivore tooth pit morphological analyses: A methodological update for digital taphonomy

Modern day investigation in fields of archaeology and palaeontology can be greatly characterised by an exponential growth of integrated new technologies, nevertheless, while these advances are of great significance to multiple lines of research, their evaluation and update over time is equally as important. Here we present an application of inter and intra-observer analysis in taphonomy based geometric morphometrics, employing robust non-parametric statistical analyses for the study of experimental carnivore tooth pit morphologies. To fully understand the influence of measurement errors in the collection of this data, our statistical assessment was performed on fully superimposed, partially superimposed and raw landmark coordinates collected from 3D surface scanning. Experimental samples used to assess these errors includes wolf and dog tooth pits used in modern day ecological livestock predation analysis. Results obtained from this study highlight the importance of landmark type in the assessment of error, emphasising the value of semi-landmark models over the use of ambiguous Type III landmarks. In addition to this, data also reveals the importance of observer experience for the collection of data alongside an interesting increase in error when working with fully superimposed landmarks due to the "Pinocchio Effect". Through this study we are able to redefine the geometric morphometric models used for tooth pit morphological analyses. This final hybrid Type II fixed landmark and semi-landmark model presents a significant reduction in human induced error, generating a more metrically reliable and replicable method that can be used for data pooling in future inter-institutional research. These results can be considered a fundamental step forward for carnivore inspired studies, having an impact on archaeological, palaeontological, modern-day ecological research as well as applications in other forensic sciences.

Interpol review of shoe and tool marks 2016-2019

This review paper covers the forensic-relevant literature in shoe and tool mark examination from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

Skull fractures in forensic putrefied/skeletonised cases: The challenge of estimating the post-traumatic interval

The objective of our study was to assess the reliability of the estimation of posttraumatic survival time (PTST) in forensic cases based on microCT and histology of putrefied/dry bone samples with comparison of initial macroscopic fracture classification performed during autopsy. Macroscopic morphological patterns of bone fracture are routinely used in forensic pathology and anthropology to distinguish between antemortem, perimortem and postmortem injuries. Based on macroscopic and microscopic analysis of six craniofacial fractures, our study results illustrate the need to complete macroscopical findings and initial fracture classification with microscopic analysis to avoid any inaccuracy. MicroCT has become a powerful technique to identify early bone healing signs but histology remains the gold standard to estimate the PTST and determine vital fracture based on hemorrhage marker. Raman microspectroscopy can identify a blood clot in the fracture line.