30/06/2020

Earlier this year, researchers at the Cranfield Forensic Institute carried out a study which showed that the use of 3D printing technology to provide evidence in court can help to improve a jury’s understanding of technical language.

The study involved a simulated courtroom exercise, with 91 mock jurors being assigned one of three visual evidence formats – either photographs, 3D visualisations or a 3D printed model – at random. The individuals were then asked questions to assess their comprehension of technical language associated with the evidence. The findings showed a 94% increase in comprehension when 3D printed models were provided, compared to 79% when photographs were used.

The researchers are now fine-tuning a 3D printing technique and have called for wider research to provide an evidence-base for the use of 3D printing in court and more widely in other forensic disciplines. Dr David Errickson, Lecturer at Cranfield Forensic Institute, said: “In order for 3D printing to be used in forensic science, particularly in courts of law, the discipline needs a recognisable evidence-base that underpins its reliability and applicability.” 

So what are the applications, benefits, and limitations of 3D printing in forensics? And where does the research need to focus now to create this recognisable evidence-base, in order for the technique to become a viable, admissible method of presenting evidence?

Applications

Currently in forensic science, the use of 3D modelling has been used mainly in a virtual format. However, as the patents that limited access to 3D printers have expired, the use of 3D printing has become more accessible which has resulted in a continuous, albeit slow, uptake of its application. [1]

The recent research from Cranfield into the potential for 3D printed models to improve juror’s understanding is just one example of how 3D technology can be applied in forensics. These replicas could be utilised across the forensic sciences – crime scene reconstructions, in the analysis and interpretation of materials and even in a teaching and public outreach setting. The possible applications of 3D printing span criminal forensics, forensic archaeology, forensic medicine and forensic anthropology.

Crime scenes, police investigations and intelligence gathering
3D printing could be used to create a scaled-down model of a crime scene, enabling complex information to be presented as a physical demonstration in a courtroom. For example, in their paperAn overview of 3D printing in forensic science: the tangible third dimension’ Dr David Errickson and Rachael Carew cite work carried out by Liscio (2013) in which a vehicle accident scene was 3D printed to help visualise its final position in relation to other objects.

Similarly, the technology could be applied to create a physical replica of a bullet’s trajectory – providing an alternative source for visualisation of a crime scene, and even possibly reconstructing bullet trajectory from within a living or deceased person.

A 3D model could also be used to scale small details, illustrating characteristics that cannot be seen on a traditional case (such as feathering in footwear evidence), and to provide forensic facial reconstructions using 3D printed skulls – which according to Carew and Errickson has led to positive identifications taking place.

Forensic archaeology, anthropology and medicine

Forensic archaeology is also discussed as a potential promising area for the application of 3D technology. Entire sites could potentially be captured using 3D recording processes, documenting features and accurately recording graves and remains in situ: “The use of 3D printing in forensic archaeology is extremely novel, but has the potential to complement forensic archaeological practices, being a useful tool for visually demonstrating features that have since been destroyed or removed through excavation.” The technology could also be combined with volumetric imaging (stacking sliced 2D images to form a volume) to print internal bony structures for analysis that would not normally be visible. 3D printing anatomy could also be used in forensic medicine to be used as a demonstrative teaching aid, and to “significantly improve the knowledge and skills of new surgeons, anatomists, anthropologists, and other professionals.”

Benefits: improved understanding, preserved evidence and less disturbance to crime scenes

The possible applications of 3D printing in forensics already begin to highlight the potential advantages and benefits, which include:

  • Interactive evidence for improved understanding.
    Implementing the technology in forensic reconstructions creates a physical 3D replica that can be handled, allowing a higher level of interaction by the observer. As is suggested by the recent research from Cranfield, the technology seems to have the potential to aid better understanding of evidence.

  • Broader range of evidence presentable in court.
    3D replicas allow for a visual representation of evidence to be presented in a court of law, that would otherwise not be permitted – for instance, while human remains themselves are not permitted in UK courtrooms, a replica would not be subject to the same ethical and safety considerations.

  • Higher level of accuracy compared to traditional methods.
    Re-enacting events using a 3D printed replica of a scene may provide a more accurate representation than traditional methods. The technology also means that complex geometries, including internal/obstructed structures, that couldn’t be captured in traditional casting methods could be printed, and a variety of colours and materials could be used when printing to better aid visualisation and interpretation.

  • Data can be retrieved through non-contact methods, creating an ethical workflow.
    Another benefit of 3D printing is that the data can be retrieved through non-contact methods, for example scanning, therefore it is an ethical workflow that doesn’t disturb human remains or trace materials. It also reduces the risk of compromising the integrity of original materials and protects fragile elements, through reduced handling.

  • Improved longevity of evidence.
    Creating a physical replica also provides a means of revising evidence long after it has degraded or the remains have been buried.

Limitations

  • Lack of empirical evidence base.
    Currently, one of the main limiting factors in the application of 3D printing technology is the lack of an empirical evidence-base demonstrating its accuracy and reliability. Carew and Errickson state that “published examples of 3D printed replicas in court are specific to demonstrative evidence and are limited to only a few cases” therefore the validation of techniques for a courtroom application have been underexplored. This lack of an evidence base also limits other forensic applications, such as forensic anthropology. The authors of a preliminary study into the accuracy of 3D modelling and printing techniques in forensic anthropology evidence reconstruction, published in 2018, also cite a similar issue with the lack of an evidence base and provide an example where the lack of validated techniques led to evidence being deemed inadmissible:

    “The issue of introducing new technology in court was highlighted in a case tried in the United Kingdom in 2016, whereby the defence counsel cast doubt on the reliability of a 3D printed cranium. At trial, it was stated that the manufacturing process had not been validated in a forensic context and was simply an interpretation, thereby undermining the weight of the evidence.” [2]

  • Industry standard ‘best practice’ technique needs to be developed.
    Questions over the best practice for the most reliable, and valid, 3D printing process current limit the extent of its application. Depending on the technique used, there could be some loss of detail, visual representation of an object could be hindered in post-processing and evidence may be oversimplified, for example through smoothing parameters. This raises the question over how much detail can actually be taken from object reconstructions and the extent to which the replica is accurately reflecting findings.

  • Questions over the most appropriate area of expertise.
    The expertise of the individual carrying out the 3D printing must also be considered. Should they be an expert in the type of evidence being replicated, forensic science, anatomy, the printing technique itself – or all of the above? When considering the potential of 3D printing, Carew and Errickson highlight that “the intended outcome of 3D imaging and printing is highly dependent on the skill set of the professional. Therefore, an appropriate background is one of the most important factors in creating 3D printed models. If this is not considered, the value of the evidence is risked in court under the examination of the expert as a witness, which in turn may make the evidence inadmissible.”

It is clear that, in order to achieve the potential benefits of 3D printing in forensic science, research focused on creating an empirical evidence base and outlining a standard of good practice will be key.

The way forward: research questions for developing an evidence base and the need for cross-disciplinary communication to validate a standardised approach

In order to progress the use of 3D printing in the forensic setting, Carew and Errickson have set out the following research questions to address:

  • How are 3D models being created, who is creating these models, and where are these being created?—what is the intended goal?
  • How and where are 3D printed models currently being used within the forensic science framework?
  • Who is best prepared to produce 3D printed models?
  • Who should defend a 3D printed model in a courtroom?
  • Do we need specific training for producing 3D printed models in forensic science?
  • Who owns a 3D printed replica in forensic science scenarios, what are the associated ethical considerations, and what happens to this data beyond the close of a case?

It is suggested that while there is work being carried out to validate the use of 3D printing in forensic sciences, this work is currently sporadic and, in order to progress, more communication across the forensics disciplines and a community effort is required in order to develop an approach which is “traceable, accurate, legal, and standardised”.

The following agenda for future work and research is set out:

  • Formation of a working group; to develop best practices for 3D printing in forensic science and to act as a validation committee for the development of protocols.
  • Development of a primer for the use of 3D printed replicas in courts of law.
  • Greater inclusivity between forensic science disciplines, multidisciplinary discussions and liaisons with other disciplines/bodies (e.g., radiology, additive manufacturing engineers, and material scientists consolidating their research).
  • Widen awareness that validation of 3D printed models in forensic science is needed.

If evidence to address the current questions of accuracy, representation and admissibility can be gathered, and an industry-wide standard of best practice developed, the use of 3D printing and the potential benefits it brings – such as better understanding for jurors and better visualisation methods for complex or sensitive scenes – could increase in the future.