Applications of micro-CT in the Criminal Justice System of England and Wales: an impact assessment

The Criminal Justice System of England and Wales is currently facing major challenges. One is the financial pressure of government funding cuts, the other the increasing need for professionalisation and rigour within the system. This thesis presents the use of micro Computed Tomography, Additive Manufacturing, and 3D visualisation to address both challenges. By drawing on data from live murder investigations the project examines how these digital technologies can be used to improve the investigation of strangulation deaths, sharp force injuries, and fractures. Each of these categories was treated as a separate case in the overall multiple-case study research design. The increased detail enabled by micro-CT assisted pathologists in the diagnosis of strangulation as previously undetected injuries of the larynx could be identified. A validation study comparing injured to uninjured samples was conducted to increase the strength of the interpretations. For sharp force injuries analysis, micro-CT proved useful for providing the necessary injury characteristics and highly accurate measurements to allow weapon identification. The high resolution of micro-CT scanning also enabled the visualisation of trauma on the smallest of skeletal elements, often encountered in non-accidental injuries in children. The cross-case synthesis revealed the main themes of clarity, objectivity, and visualisation which were improved by using micro-CT irrespective of type of homicide. The significance of these themes further crystallised in semi-structured interviews conducted with various stakeholders of the Criminal Justice System. Management concepts proved suitable to assess the project’s success as the themes used in operations management such as quality, delivery, and cost apply to the delivery of justice as well. A good working relationship with West Midlands Police’s homicide investigators and researchers at WMG was crucial to providing the technology and expertise to address real-life problems whilst ultimately saving taxpayers’ money

Introducing 3D printed models as demonstrative evidence at criminal trials

This case report presents one of the first reported uses of a 3D printed exhibit in an English homicide trial, in which two defendants were accused of beating their victim to death. The investigation of this crime included a micro-CT scan of the victim's skull, which assisted the pathologist to determine the circumstances of the assault, in particular regarding the number of assault weapons and perpetrators. The scan showed two distinct injury shapes, suggesting the use of either two weapons or a single weapon with geometrically distinct surfaces. It subsequently served as the basis for a 3D print, which was shown in court in one of the first examples that 3D printed physical models have been introduced as evidence in a criminal trial in the United Kingdom. This paper presents the decision-making process of whether to use 3D printed evidence or not

Using micro computed tomography to examine the larynx in cases of suspected strangulation- a comparison of case findings and control images

The examination of strangulation is one of the most challenging cause of death diagnoses encountered in forensic pathology. The injuries are often subtle and difficult to detect, especially in cases that lack superficial marks. Fractures of the laryngeal skeleton are commonly regarded as evidence of strangulation but these can be too subtle to be detected during autopsy. Micro-CT is a novel imaging technique that achieves a spatial resolution 1µm or less which lends itself to the examination of small and delicate structures such as the larynx. However, there is little information to date regarding the appearance of the larynx at this scale, thus complicating the interpretation of the micro-CT images. This study therefore uses micro-CT to examine ten larynges from strangulation deaths and to compare them to nineteen samples from donor individuals in order to distinguish between naturally occurring features and actual trauma. It was found that there are several features which mimic damage in the donor group. Using associated case information, initial trends and patterns of different strangulation methods were established

A holistic multi-scale approach to using 3D scanning technology in accident reconstruction

Three-dimensional scanning and documentation methods are becoming increasingly employed by law enforcement personnel for crime scene and accident scene recording. Three-dimensional documentation of the victim’s body in such cases is also increasingly used as the field of forensic radiology and imaging is expanding rapidly. These scanning technologies enable a more complete and detailed documentation than standard autopsy. This was used to examine a fatal pedestrian-vehicle collision where the pedestrian was killed by a van whilst crossing the road. Two competing scenarios were considered for the vehicle speed calculation: the pedestrian being projected forward by the impact or the pedestrian being carried on the vehicle’s bonnet. In order to assist with this, the impact area of the accident vehicle was scanned using laser surface scanning, the victim was scanned using postmortem CT and micro-CT and the data sets were combined to virtually match features of the vehicle to injuries on the victim. Micro-CT revealed additional injuries not previously detected, lending support to the pedestrian-carry theory

Advantages of micro‐CT in the case of a complex dismemberment

This case study reports the advantages of micro-CT to aid the investigative process in a complex dismemberment case. Micro-CT was successfully implemented to scan all skeletal remains of a dismembered female. The digital models were utilized to (i) screen for any further injuries not related to the dismemberment, (ii) provide measurements from false starts non-destructively, and (iii) visually represent the evidence in a structured format in court to improve the understanding of the forensic evidence by the jury. Acquiring high-resolution scans in this manner improved the efficiency of the forensic investigation by screening the remains and provided complementary toolmark evidence to the investigating team and forensic pathologist. A total of 14 false starts were identified along with the directionality of each dismemberment cut. Furthermore, the visual 3D representation of the remains in court provided a powerful tool to communicate this important evidence to the jury and form a prosecution narrative. As a forensic radiological method, micro-CT provided valuable information both in the investigation and the court presentation

Accurate prediction of saw blade thicknesses from false start measurements

Background: False start analysis is the examination of incomplete saw marks created on bone in an effort to establish information on the saw that created them. The present study aims to use quantitative data from micro-CT cross-sections to predict the thickness of the saw blade used to create the mark. Random forest statistical models are utilised for prediction to present a methodology that is useful to both forensic researchers and practitioners. Method: 340 false starts were created on 32 fleshed cadaveric leg bones by 38 saws of various classes. False starts were micro-CT scanned and seven measurements taken digitally. A regression random forest model was produced from the measurement data of all saws to predict the saw blade thickness from false starts with an unknown class. A further model was created, consisting of three random forests, to predict the saw blade thickness when the class of the saw is known. The predictive capability of the models was tested using a second sample of data, consisting of measurements taken from a further 17 false starts created randomly selected saws from the 38 in the experiment. Results: Random forest models were able to accurately predict up to 100% of saw blade thicknesses for both samples of false starts. Conclusion: This study demonstrates the applicability of random forest statistical regression models for reliable prediction of saw blade thicknesses from false start data. The methodology proposed enables prediction of saw blade thickness from empirical data and offers a significant step towards reduced subjectivity and database formation in false start analysis. Application of this methodology to false start analysis, with a more complete database, will allow complementary results to current analysis techniques to provide more information on the saw used in dismemberment casework

Micro-CT for the examination of paediatric rib injuries : a case series

Cases of child abuse and homicide are amongst the biggest challenges investigators face, with complex evidence bases often strongly contested and reliant on specialist interpretation of the medical evidence. In many cases, this medical evidence includes examination of the deceased’s skeleton using different macroscopic and microscopic imaging methods. Rib fractures are a common concern when examining suspicious cases and much research has been conducted on their causes. The role of CPR in particular has been controversial and therefore a clear assessment of the fracture distribution is crucial. Recent studies have shown the benefit of imaging techniques such as Computed Tomography, although the gold standard remains histology. This paper presents three cases of suspected non-accidental rib fractures of infants which had been examined using micro-CT and histology. Micro-CT has been shown to be superior to medical CT as it achieves a greater resolution, making it effective for paediatric post-mortem imaging. Micro-CT observations were compared retrospectively to the histology, which demonstrated that micro-CT found 69% of the fractures identified histologically as well as an additional 22% not identified through histology. As well as complimenting histological analysis, the extent to which micro-CT can enhance the overall examination of paediatric non-accidental injuries is also discussed

Using histology to evaluate micro-CT findings of trauma in three post-mortem samples — First steps towards method validation

Forensic imaging technology has rapidly advanced over the past several decades and is gaining increasing significance in medico-legal death investigations. Medical-grade computed tomography (CT) is now routinely used in post-mortem examinations at numerous institutions across the globe. However, the resolution of medical-grade CT is limited and unsuitable when used to depict some smaller anatomical structures or micro-trauma. High-resolution micro-CT offers up to 100× the resolution to overcome this problem but is a very recent addition to the field of forensic radiology. Few studies so far have attempted to validate the results which is an essential prerequisite for it to be used in the criminal justice process as demanded by regulatory bodies. This study directly compares micro-CT images with histology, the current gold standard. Three cases were examined: two larynges from suspected strangulations and one ribcage of a case of fatal child abuse. A strong correlation was observed between histology and micro-CT as the majority of skeletal injuries were identified correctly. This paper discusses the forensic implications of the results and how micro-CT is complementary to histology

Forensic 3D printing from micro-CT for court use- process validation

Forensic application of 3D scanning and printing technology is gaining momentum with 3D printed evidence starting to be produced for court. However, the processes for creating these forensic 3D models requires still rigorous assessment to ensure they adhere to the relevant legal standards. Although, previous work has examined the accuracy of 3D prints created from medical grade Computed Tomography (CT), no such assessment has been carried out for Micro Computed Tomography (micro-CT) which offers superior resolution and the ability to capture forensically relevant injuries. This study aimed to quantify the error rates associated with forensic 3D printed models and toolmarks, created using three different printing technologies, based on micro-CT data. Overall, 3D printed models, based on micro-CT scans, replicate bone surface geometry to sub-millimetre accuracy (<0.62 mm for overall shape and <0.36 mm for toolmarks). However, there were significant differences between the printing technology employed (mean errors of −0.3%, −0.8%, and 0.7% for shape geometry and −0.8%, 14.1%, and 0.7% for toolmark geometry for Printers 1–3 respectively). Where possible, the authors recommend micro-CT imaging for producing forensic 3D printed bone models particularly when injuries are present