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Mapping a crime with forensic scene visualisation 

CRJ Key Network Partner, Pix4D investigates how a law organisation uses photogrammetry to recreate detailed crime scenes and incidents for legal investigation.

Using photogrammetry to create a stunningly detailed model of a Californian mountainside after a wildfire. All photos courtesy of Visual Law

When making a decision in court, juries have to weigh up evidence and accounts from both sides. This is a huge responsibility, as the jury’s judgement can significantly alter people’s lives. Evidence presented to the court must be accurate and tell a story about the crime scene. But what about the scene itself? Photogrammetry can bring the event into the courtroom for all to see and judge for themselves.
A former plaintiff lawyer, Mark Johnson is the CEO of California-based Visual Law Group, which offers services in collision reconstruction, modelling of crime scenes and video reconstruction. This innovative use of photogrammetry, called forensic scene visualisation, is used to recreate crime scenes or events for presentation in the courtroom.
To ensure that the recreations are admissible in court, it is necessary to establish underlying accuracy and fidelity to the real-world scene. This is critical in crime scene investigations, such as for traffic collisions, where significant compensation or consequences rely on the outcome of the investigation. After the foundational elements for admissibility are established, the visualisation may be presented to the jury, who will use the evidence in deliberating their verdict.
Experience has shown that juries appreciate and are often favourably influenced by viewing 3D depictions of crime scenes or events under consideration. Thus, the judge, who must rule on admissibility, typically requires fastidious proof that the 3D data is properly scaled and created using methodologies accepted by professionals within the field. 
Johnson uses Pix4Dmapper to create his 3D models from images in the majority of his cases and routinely provides counsel with several white papers and other references to be provided to the court, which confirm the software’s precision and accuracy. Johnson uses the Pix4D-generated point cloud and orthographic image with third party software to add details, lighting and moving elements to enhance the courtroom presentation.
In September 2020, Johnson was interviewed on KSL TV, a television station based in Salt Lake in Utah, USA, regarding his work in forensic scene visualisation in criminal cases. At the station’s request and with its assistance, Johnson created a 3D model of a property under investigation in a high-profile criminal case, which could be used to cross reference claims made in court by both the prosecution and the defence.

The scene above shows a crime scene at a property in Utah, USA where identifying the suspect's line of sight and the location of buried murder victims ratified the court's decision

The workflow for creating these models begins with flying a drone around the crime scene to collect images that are then processed on a desktop computer in Pix4Dmapper. Johnson and his team can then manipulate the models with other specialised software to reflect the conditions at the time, for example to animate a storm to imitate the weather when a crime or event occurred.
As Johnson explained to KSL, the objectivity of using aerial photogrammetry in 3D modelling can help collect evidence that is of a high enough accuracy for crime scene investigations. Much like photographs or video footage, a 3D recreation of a crime scene presents facts that the jury can interpret for themselves. Unlike traditional photos, a 3D visualisation may be viewed from any vantage point, under different lighting conditions and with the added capability of permitting measurements to be made in real time. Special attention needs to be paid to the level of detail of the work, making an exact copy or digital twin of reality available for analysis. 
The models can present unimaginable scenarios to a jury that is detached from the crime. Pix4D software is focused on accuracy and in these situations, accuracy can mean truth. It shows in detail how events unfold and their effects. Although they not used specifically in the case above, the projects created by Visual Law Group of the property were compared with footage of court proceedings by KSL TV to ratify statements about the property.
When commenting on the impartiality of the footage, Johnson says: “It has to be absolutely to scale. It has to be non-prejudicial. It cannot be biased in favour of one party or the other.” 
The unbiased account provided by forensic scene visualisation has been used in other cases. Visual Law has successfully submitted models and video recreations of scenarios in court on behalf of both the prosecution and defence in various cases. This has included recreating a military helicopter training accident in Virginia and the movement of waves during a snorkelling accident in Hawaii.

 Johnson created a highly detailed model of an atoll in Hawaii to highlight the wave movement following a snorkelling accident

Bringing a crime scene to the courtroom is revolutionary, where people on both sides of the case can walk through every detail of an event, even if the crime took place months before. For juries and litigators alike, this reminds them that the justice processes in the room are ruling on real situations, not abstract concepts – they can see the digitised reality of the event for themselves.

Thumbnail:  Hilaludin Bin Abdullah Hilal/123rf

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