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17/02/2009
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Tom Shelley reports on the growing application of 3D CAD to engineering and human forensics
Police in Switzerland are routinely analysing crimes, accidents and fires using the latest scanning technology and techniques to piece together events in a CAD model. The subsequent analysis is making it easier for investigators to find out exactly what happened and what was responsible. As a result, it is increasingly being used by police forces in the UK and the rest of Europe to help improve designs and to prevent bad things from happening again.
The Scientific Forensic Service and the Technical Accident Reporting Service of the Zurich City Police uses photogrammetry, 3D laser scanning and Autodesk 3ds Max. For traffic accidents, the Zurich City Police use a flexible optical measuring machine, essentially capable of scanning an environment and virtually recreating it in 3D. The Atos scanner, made by German Measuring Techniques specialist Gom, is used in conjunction with a laser scanner made by Leica to capture details of at the scene of an event and the objects within it.
The meshed 3D surface models from the scanners are imported into 3ds Max as Specification and Description Language (SDL) data. “For us the use of 3ds Max is the most efficient and simplest way of understanding what really happened,“ says Marcel Braun, head of special measurements for Zurich City Police. “It’s not just about visualising it but about having many different perspectives to hand and being able to test each option.”
Across the Atlantic, J2 Engineering used scene modeling with AutoCAD in a landmark investigation. In 2004 it proved that a Chevrolet Blazer involved in a rollover collision with a police car was in fact going at 82 mph, and not the 60 mph claimed by the driver.
A leading practitioner of what is called, “Forensic Engineering”, is Knott Laboratory in Denver, Colorado. It has applied CAD techniques to analyse the crash that killed Princess Diana and concluded that if there had been a guardrail in the tunnel, nobody would have died. Even without it, Princess Diana would probably still be with us if she had been wearing her seat belt.
Back in Switzerland, 3D CAD supported photogrammetry, has been used to show that a murder victim had in fact been killed with a spanner, not with a hammer as had first been thought. Footprints and tool marks have been scanned from around the world in order to make it easy for investigators to find a match. One of the most common, and useful, forensic applications of CAD and virtual reality is to reconstruct crime scenes to evaluate what witnesses could really see, as opposed to what they think or say they saw.
Forensic Reconstruction
A project known as Virtopsy is being carried out by the Institute of Forensic Medicine at the University of Berne. It is developing technologies and techniques that it hopes will lead to minimally invasive autopsies.
Using imaging techniques such as CT and MRI scans, photogrammetry and 3D optical measuring techniques, a reliable and accurate geometric presentation of all forensic findings can be made which allows an exact reconstruction to be produced. One of the techniques the project aims is to develop the use of MR-Spectroscopy to estimate, for example, the time of death.
The multi-disciplinary project involves forensic sciences, diagnostic imaging, magnetic resonance spectroscopy, computer sciences and telematics as well as biomechanics.
Pointers:
* 3D photogrammetry is now quite widely used in forensic investigations, especially to study footprints, tool marks, and the impact of instruments including teeth on the human body
* Computer based 3D modelling of industrial and traffic accidents is more complex, but can yield information of immense benefit, in not only determining what really happened, but hopefully preventing such things happening again
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Author
Tom Shelley
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