Validation

Working closely with other experts led to the realisation that an ideal work process would be to conduct the micro-CT scan, process the scans, and then analyse the images together in order to allow the histopathologist to plan their procedures accordingly. This would improve the correlation between the two methods which has the potential to further validate micro- CT as a method and develop its use further, possibly allowing fracture ageing at some point in the future. Few studies have examined fracture age using micro-CT as it is a difficult experimental set-up (Shefelbine et al. 2005, Morgan et al. 2009). A validation study was therefore conducted as part of this PhD project comparing the micro-CT manifestation of fractures to that of histology, albeit not focussing on the fracture age but rather on the presence/absence. This study found a good correlation in the detection of bone fractures but recommends further research on a wider range of samples. The complimentary nature of histology and micro-CT is most pronounced for fracture dating. Calluses of varying degree of maturation have been observed on the micro-CT scans but little research has been done in this field and there are many factors which influence the callus appearance, thus making it difficult to provide precise timings for an injury. In the context of suspicious rib fractures one needs to be aware of the effects of CPR which can sometimes cause the ribs to fracture. While these fractures tend to be found on the anterior aspects of the ribs (Stöver 2007, Weber et al. 2009), a precise timing can only be provided by histopathology. Validation studies are an essential requirement in forensic contexts as previously discussed for strangulation injuries in Chapter 5. In sensitive areas such as child deaths they add an important level of certainty which these cases often lack (Lynøe et al. 2017). The literature review in Chapter 2 has outlined how forensic science evidence has contributed to many miscarriages of justice to which child cases seem to be particularly prone. The problem with the forensic evidence in child cases is often the reliance on opinion evidence (Betts 2013)

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and a lack of empirical data which is the issue addressed by validation studies. Improving the correct diagnosis of such cases even minutely has the potential to prevent miscarriages of justice from happening and thereby contributing to improve the quality of forensic evidence enabling fairer trials which benefits the whole of society.

The final societal benefit affecting child cases is the public perception of the investigation process. The public and all other stakeholders want to see progress being made but this public pressure to convict a culprit has been partially responsible for investigators’ readiness to accept flawed expert testimony in the past (Findley and Scott 2006). Demonstrating that all available resources and technological advances are being exploited can reassure them that police have left nothing untried and raise confidence in their work.

5.3 Visualisation

The visual output of the micro-CT scans of blunt force injuries is a further benefit observed irrespective of the type of case examined. 3D models, both virtual and physical, can increase the comprehension of the fact finder as several studies indicate (Urschler et al. 2014, Petersson et al. 2009) and which multiple interview respondents confirmed (see Chapter 9). Any visualisation of traditional autopsy evidence, especially from child deaths, in court is problematic as it is considered too emotionally upsetting for the jury (Errickson et al. 2014). However, the micro-CT models were perceived as sufficiently abstract since they only showed selected elements that were less reminiscent of an actual individual. A selection of images shown during the trial of OP Rococo is provided in Figure 38. Displaying these models digitally in larger-than-life further reduced the perception of the sample as being an actual human infant body part. 3D prints were more contentious to introduce as evidence as they were printed on a 1:1 scale, reminding people again of the reality and the vulnerability of such a small human being. The researcher observed this effect on themselves as well. Despite having scanned and examined the original samples of OP Rococo it was not until holding the 3D prints that they became fully aware of the size and fragility of the victim. This sparked feelings of disbelief how someone could cause such injuries to a child and also anger towards the perpetrator(s). This effect has also been noted by Bright and Goodman-Delahunty (2006) who studied the effect of graphic images on a mock jury. They found that by showing them such images their rational decision-making decreased while the likelihood of a guilty verdict rose. Forensic scientists are not immune to these effects. Subconscious bias can, as shown in Chapter 2, cause the forensic scientist to draw rash or incorrect conclusions based on the circumstantial information they received prior to their examination (Bernstein 2008). The dilemma in practice is that on the one hand some information is necessary to adequately

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interpret the findings, on the other hand too much information might lead to the scientist seeing what they expect based on the information. The dangers of cognitive bias is becoming increasingly recognised in forensic science and careful case management is required to mitigate the effects (FSR 2015).