Forensic evidence is easily misinterpreted, leading to wrongful prosecutions. A new, crowdfunded UCL lab is aiming to prevent this
From Sherlock and CSI to the high-profile trials that get reported in the media, we know that forensic evidence can be the key to unlocking cases and getting a conviction. What the TV shows don’t tell us is that, while the technological capabilities to detect forensic evidence are increasing all the time, there is still a significant gap in our knowledge that makes interpreting what evidence means highly problematic.
To interpret forensic evidence properly requires a significant and systematic research base to refer to — and this is something that Dr Ruth Morgan, Director of the UCL Centre for the Forensic Sciences, is passionate about developing.
Morgan and her colleagues set up the centre in 2010 — just as the coalition government announced its decision to close the Forensic Science Service, a national provider of specialist services and a significant source of research and development.
As a result, she says, one of the centre’s aims is to fill this gap and create a body of research to match the huge advances in forensic techniques, which will focus on how to interpret evidence better.
“How can we make evidence-based decisions at the crime scene, how can we make sure we’re collecting the right evidence, looking for the right evidence in the right places, and then when it has gone through robust and valid analysis, what does it mean? What’s interesting is that there are a lot of assumptions that we have those answers already.”
Making those sorts of assumptions can potentially have a serious impact on someone’s life and liberty. Dr Morgan worked on one so-called ‘cold’ case where a prisoner was serving a sentence for murder and the prosecution’s case rested on a group of metallic particles that were present on the victim’s clothing and in the suspect’s vehicle.
She says that, when presented with this forensic evidence, the prosecution team made two key assumptions. “One was that these particles were very rare and, therefore, 13 particles on the skirt and five particles on the vehicle were highly significant — demonstrating evidence of contact very shortly before the body was deposited. The second one was that, because they were very small and spherical, they would fall off very quickly.”
The fresh examination showed that the source of these particles was actually fairly common, thousands of them were produced on a regular basis and that the victim had been in a number of different environments that evening where these particles would have been present in significant numbers.
“I find the public perception of DNA quite shocking. People obviously do think, ‘Oh, DNA match — must be guilty’.”
Next, the team did a series of persistence studies. “We got items of clothing that were the same as the victim’s, then we found the make of the van and actually got a seat from a similar model and did some experiments. And we showed that after 18 hours, 25% of the particles were still there, so they didn’t fall off nearly as quickly as had been assumed.
“With those two bits of information, we were able to present a case that essentially undermined that critical evidence.”
Indeed, with some additional lines of evidence, the defence was able to take the case to retrial, the conviction was quashed and, with the subsequent re-opening of the case, another suspect was identified through a DNA hit.
Misinterpreting the smoking gun
One of the most significant types of trace evidence at a crime scene is gunshot residue (GSR). Dr James French, a Teaching Fellow at the Centre for the Forensic Sciences, specialises in the interpretation and analysis of GSR.
One of the challenges for him is the continuing prevalence of certain assumptions — now considered outdated — about the number of particles necessary to indicate that someone was involved in firing a gun.
“There was a piece I once read where there was a FBI set of guidelines suggesting that between three and five particles is enough to start saying with some certainty that that couldn’t just be a background quantity. But actually in certain environments, it’s been shown that there are quite high levels of GSR in the background. In police facilities — particularly in the US, but also in the UK — if there are tactical firearms units there, you would expect there to be some level of background GSR.”
The analytical challenges don’t stop there, though: a number of different particles elementally look very similar to GSR. “It’s been shown that there are very similar particles in fireworks,” says Dr French, “and in different parts of cars, such as brake linings and engine cylinders, which could lead to somebody misinterpreting the presence of material, particularly if they were untrained.”
“Our analytical capability is much, much greater than it was and we’re now able to discern with greater certainty between environmental particles and GSR. But that doesn’t take away the interpretation problem around the significance of finding particles. We did some work that suggested you could actually acquire quite high levels of residue simply by handling a firearm — you don’t necessarily need to have fired it.”
To address this interpretation problem, Dr French uses a Bayes Nets approach to examine various different people within a scenario and the strength of evidence in each instance.
He explains: “Within this Bayesian paradigm, you need to assess the presence of the evidence under two different theories about how it got there. So, one will amount to the prosecution’s assertion, one will amount to the defence’s assertion, and in order to assess the significance of the evidence under each theory, you need empirical data.
“With a lot of the work that we do here at the centre, the aim is that the experiments that we undertake and the data that we produce can be used to inform the interpretation of evidence and what is, ultimately, presented in court.”
Debunking DNA myths
The evidence that is often the most crucial at trial and, therefore, most captures the public’s imagination, is DNA.
Dr Georgina Meakin, a Lecturer in crime and forensic science, completes the CFS team, running its collaborative DNA facilities. The focus of her work is forensic DNA analysis, particularly investigating how easily it can move around and how long it can persist in different scenarios.
“I find the public perception of DNA quite shocking,” she says, “because people obviously do think, ‘Oh, DNA match — must be guilty’. That’s really not the case at all, especially in recent years. Our analytical technology has become so sensitive that we can now get full profiles from just a handful of cells.
“To put that in context, on the head of a pin you can get 10,000 cells, so we’re talking about very, very small amounts of material — which means that DNA can be left when you touch something, when you speak in the vicinity or cough or sneeze.
“But more than that, DNA can be indirectly-transferred, that is, your DNA can end up on an item that you’ve never touched or in a room where you’ve never been. For example, if you shake hands with someone, they can then touch something and leave your DNA on the item that they’re touching.”
Dr Meakin says that one of the CFS’s aspirations is to educate everyone involved in the criminal justice system to ensure that all types of evidence, not just DNA, are given the correct amount of evidential weight in court.
And, for her, this is one of the most exciting aspects of the job: “What I really like about forensic science is being able to do research where you can see the direct, real application and how it can affect everyday life straight away.”
Sewer water and homemade explosives
One of Dr Morgan’s recent PhD students, Sally Gamble, is similarly enthused about using forensic science to address real-world problems. During her studies, she became aware of research involving the monitoring of illicit drugs in river water and how this could enable researchers to calculate estimated levels of drug consumption in a given population.
At this point, inspiration struck. “I had the idea to monitor trace homemade explosives in the water system to see if we could detect these substances in the first place and then whether this could identify a geographical region where any of these explosives might be being manufactured.”
Having identified methods in the lab for detecting the chemicals, she set up collaborations with King’s College London and a number of other labs, including Natural Resources Wales in Llanelli, South Wales.
Sally’s efforts then moved from the theoretical to the very practical — spending many nights wading through sewers to collect samples. “I had a designated freezer to keep all my sewage samples in — nobody seemed to want to store any sewage in their own freezers — so I’d often be seen marching around campus with a 85-litre backpack, transporting samples and equipment!”
Working with Thames Water and the Environment Agency, Sally’s research had direct, practical applications. “I developed a small passive sampling device that could be placed into the sewers as part of a small-scale surveillance operation in a geographical location that was already under suspicion.
“The information regarding the architecture of the sewerage system would then allow a strategic sampling protocol to be implemented to try to capture samples that would narrow down their origin as closely as possible,” she explains. “These devices could be deployed discreetly (at night with Thames Water) and left to sample for 2–3 weeks, then collected discreetly and analysed in the laboratory for traces of explosives and related chemicals.”
Sally’s work on the project led to a job at the UK’s Defence Science and Technology Laboratory (DSTL) and is just one example of the partnerships that CFS’s PhD students have developed with industry. Other partners include the Ministry of Defence, DSTL, the Home Office’s Centre for Applied Science and Technology and Foster + Freeman Ltd.
On the research front, Dr Ruth Morgan and her colleagues have collaborated with the Brazilian Federal Police and the Victoria Police in Melbourne, while in the UK, they have worked with the Metropolitan Police and the City of London Police, as well as equipment producers such as Oxford Instruments and forensic science departments in several other universities.
Falling between the cracks
However, in spite of this collaborative strength, the centre suffers, as forensic science does generally, from a lack of obvious funding sources.
“The research councils in the UK fund huge amounts of research, but there’s no council that has forensic science in their remit,” says Dr Morgan, “so you end up applying to different councils in cross-disciplinary calls that can often mean you fall between the cracks.”
“The other issue is that a lot of what we’re doing is taking technologies and approaches from other disciplines and customising them so they’re appropriate for the questions that need to be asked within the forensic sphere, and it’s quite difficult to explain to a research council where the novelty lies in that.”
As a result, Dr Morgan has decided to take a novel approach to addressing this funding gap: crowdfunding. She explains: “We are partnering with Crowd.Science (a crowdfunding platform for science research) and the advertising agency, Ogilvy, who have helped us pro bono to develop our messaging around the importance of doing this research and the impact it will have in the real world.
“Once you’ve looked through a scanning electron microscope, you’ll be hooked. It’s just incredible what you can see in just day-to-day things.”
“It’s exciting to have the opportunity of raising the visibility of this issue and the need to address the huge gap that we have in our ability to interpret evidence accurately, reliably and transparently.”
The key aim of the campaign is to attract sufficient funds to enable the Centre for the Forensic Sciences to create a dedicated research facility where the interpretation of evidence is carried out in a truly focused interdisciplinary manner. The facility will provide a platform to establish collaborations with investigators and lawyers to develop bespoke research projects that will provide the evidence base needed for real cases.
However, Dr Morgan also wants to inspire in people the fascination for forensic science that she still feels. “Once you’ve looked through a scanning electron microscope, you’ll be hooked,” she says. “It’s just incredible what you can see in just day-to-day things — the intricacies and diversity within that environment.
“My vision is that we will raise up a new community of people who are interested in the science and the impact that it can have, curious about the questions that we don’t have answers to and who want to partner with us to produce the answers that need to be found.” ■