Digital imaging has many uses in the field of forensics, encompassing a broad spectrum of disciplines from body reconstruction and visualisation to crime scene reconstruction and injury mapping. We caught-up with Alecto Forensics’ digital imaging specialist David Harrison to discuss how forensic imaging can be used to help build a case.
What are the different types of forensic imaging?
Body reconstruction and visualisation allows for the 3D digital reconstruction, interaction and depiction of the human form in a non-graphic virtual manner. These imaging modalities can be used in a variety of different ways, from demonstrating the presence or absence of body parts or bones to illustrating the scatter or placement of human remains across a crime scene.
The virtual reconstruction of crime scenes can be optimised for use on a computer screen or interaction within a virtual reality space. They can provide an invaluable aid to understanding complex scenes – such as fatal fires, structural building collapses, and explosions.
In order to present the visualisation of injuries in court, the defence or prosecution would use photographic images placed on a digital mannequin to allow a jury to better understand the relationship between different injuries. Clearer depictions of injuries can assist with the communication of vital case narratives, with timed visuals of multiple injuries also allowing for easier contextualisation. What’s more, intricate shading and texturing from injury or post-mortem injuries allows for the highest level of fidelity with observed physical trauma. Age discolouration of bruising and fibrous texturing of scar tissue can also provide clear distinction between the timing of injuries.
At any point in the visualisation, computer constructed images can be merged with injury photography to integrate the original evidence capture. In terms of criminal proceedings, they are highly effective tools when used to present explicit or graphic evidence in court.
What is a client typically looking to achieve from forensic images?
No one brief is ever the same – they vary quite considerably depending on the narrative that the client is keen to project. For instance, if the Crown Prosecution Service (CPS) is prosecuting a murder, those working on the case will want to have a fair amount of impact in the images. They’re not looking for plain presentation of data and would want injuries that actually look like injuries. However, when working on cases of victim recovery in major disasters, for example, they’d look for the opposite, for less offensive, crash test dummy type figures, so not to cause further upset and distress.
When provided with a brief, digital imagists tend to ask in advance about what kind of representation the client wants. In cases of injury mapping, clients are usually seeking something that looks realistic. This involves recreating wounds as they appear in the post-mortem photographs, but the person remains more non-descript. In short, the injuries will look authentic, but the person won’t. With the CPS, they want their images to have some emotional impact that will further the narrative that they’re giving when presenting their case.
This is because the police will want to capture attention and make some sort of impact on the jury. Very dry, data-driven presentations would do anything but that. At the end of the day, the aim of a court case is to sway the opinion of the jury.
What are the common misconceptions about forensic imaging?
People tend to presume that digital imagists have more access to information about the cases than they’re provided with. They’re usually provided with only the information needed to complete the imaging. Usually this will be scene photographs, scaled plans or sketches. If completing injury mapping, they’re provided with post-mortem report and post mortem photographs, but other than that they don’t really know anything else about the case.
What are the most common case types that utilise forensic imaging?
The work is often varied and wide ranging. While the bulk of the workload often centres around murder cases, it can also include public inquiries, industrial accidents, body recovery, fire investigation and missing persons cases.
What are the challenges associated with these types of cases?
Each type of case presents its own unique set of challenges. In public inquiries and industrial accidents, they tend to involve more work due to the multitude of rubble and the number of bodies involved. Whereas if tasked with reconstructing a murder scene and there’s just one body involved whereby they don’t need to be dug out, the crime scene tends to be ‘quieter’ with fewer different factors and aspects to consider.
Which software packages are normally used?
There are a number of different software packages that come into play with forensic imaging. Houdini is a node-based software and has many advantages, but perhaps most importantly from the police’s perspective, it has a strong commercial advantage. The benefit of using a node-based, non-linear workflow over a traditional linear one is the speed of design iteration, along with the ability to revise small parts of a model without affecting other parts or operations. This allows much faster turnaround when it comes to final revisions for a 3D reconstruction.
Houdini can also be used to edit laser scanning data and point clouds. For more organic sculpting, ZBrush is the go-to. The 3D models are then textured inside Adobe Substance Painter 3D and rendered with NVIDIA Iray, a non-biased photorealistic render engine. Some animations require the work to be sent off to third party “render farms” to ensure fast turnaround for the huge amount of processing required to render even short 3D animations at the high resolutions required for professional presentation.
Alecto Forensics is a UK leading forensic imaging service provider, delivering specialist forensic services and expertise to police forces across the UK.
We have over twenty years of forensic imaging experience within major crime investigation and provide ourselves on being an independent, quality-driven forensic service provider. We have a host of accredited experts and our expertise is available 24 hours a day, 7 days per week.