CSI: the (metro)logical approach

I grew up watching CSI, probably from a bit too young. As I grew older, I gravitated more to true crime documentaries. I found the real world to often be more interesting, albeit more morbid, than the fictional when it comes to crime. One thing that bothered me with things like CSI is the gratuitous use of non-existent or far-fetched technologies to gather evidence or reconstruct crime scenes. It’s more than a little jarring when scant evidence collected by some hotshot cop wearing no more PPE than a single latex glove is perfectly reconstructed using a hologram back at ‘the lab.’

But we’re now in 2022. Things that were TV-fiction in the early 2000s, sometimes are reality now. Granted, we might not quite be at this level, but technologies that are used to solve crimes nowadays would have baffled detectives in the nineties. Nonetheless, advanced metrological equipment that’s usually reserved for industrial applications has more than proven its mettle in the field of forensics, as well as being used in the courtroom.

I read a terribly interesting essay yesterday concerning the use of 3D printing in a wide variety of cases in England and Wales. I will only lightly touch on its main points here, but I highly recommend giving it a read, which you can do here. Each of the examples had to include a form of 3D scanning, to reproduce a demonstrable piece of evidence. This mostly meant CT scans and interestingly, in some of the cases the crime considered was assault, meaning the CT scan was taken of a living person. A CT scan, as a common medical procedure, is nothing new, but what’s interesting about this is that an exact replica of the victim’s skull and the damage to it, was 3D printed so that it could be used in order to show the extent of the attack. For the image above, in Case Example 7, the defence decided that it wasn’t necessary to show the 3D printed skull in court, as they already had more than enough evidence. In Case Example 8, however, a forensic pathologist who had only seen a CT scan, was able to provide an additional statement on the nature of the damage, as the skull fractures had not been visible externally. Paired with an additional statement on the technical details of model production, the perpetrator was convicted of attempted murder.

One case involved the murder and dismemberment of an adult male, who was then buried in a clandestine grave in the woods. The suspect possessed a saw, which the investigation believed may have been used in the dismemberment of the body. By scanning both the saw and in particular a bone that was not fully cut through, it was possible to replicate segments of both which showed perfectly how this saw fit the cut in the bone. As the essay mentions, “This case demonstrates a novel example of an interactive visual model that was used to help the jury to understand the key events from the crime.”

Other examples of remains showing damage from dismemberment being recreated in 3D printed models highlight just how useful this technique is in demonstrating what happened: looking at a bone-coloured, life-size print model with clear kerfs cut into them is quite a visceral image, whereas looking at a 3D computer model is quite a distanced piece of evidence.

In a suspected murder, although no body was found, a suspect was still charged. A small freezer was recovered from the suspect’s premises “with the working theory being that the victim had been dismembered and stored within the domestic freezer.” To ascertain whether this would be possible, a woman of similar size and build to the victim was fully scanned in 3D. The digital model had her features smoothed out to remove her identity and was then virtually dismembered along the lines that are most common. These parts were then printed to demonstrate that it was possible to fit the victim’s dismembered remains into this freezer.

In another case, a body was dismembered and placed into multiple suitcases. Older investigations would only allow inspection of the remains by opening up the suitcases and documenting the process. However, CT scans allowed the investigation to scan the suitcases before physically examining them, resulting in much more precise data before the evidence ever had to be disturbed.

Faro has published several interesting case studies relating to forensics, including ’10 reasons to use laser scanning for forensics’ and ‘3D Laser Scanner positions jury at the scene of a murder’, which expands the scope of a scan from single pieces of evidence to an entire crime scene spanning a considerable area. This allowed the jury to essentially fly around the crime scene and see it from different perspectives. This was especially useful because the defence of the suspects argued that it was debatable how much the eyewitnesses would have seen from the positions they were in. The 3D scan showed that the witnesses’ statements were true.

Clearly, advanced metrology is applicable in the real world to solve grave issues. The highly advanced instruments, from CT scanners to lasers, especially when paired with 3D printing to produce a tangible, demonstrable piece of evidence, not only provides accurate evidence, but improves the accuracy of the assessment of specialists, such as forensic pathologists. So I think it’s safe to say we’re not too far removed from that CSI hologram after all.