Can Science Prove Whodunnit?

Does forensic science really have all the answers, or are we letting it mislead us?
03 May 2016
Presented by Georgia Mills
Production by Georgia Mills.


This week on the Naked Scientists, we've got science on trial! We look at real case studies, finding out how forensics can both help and hinder criminal investigations, including the insects who are first on the scene, how your phone can tell tales, and why DNA can lead you on a wild goose chase.

In this episode

How much of you is actually human?

01:51 - Insects: first at the scene

Police are almost never the first at the scene of a murder: blow flies can arrive in just 15 seconds.

Insects: first at the scene
with Dr Martin Hall, Natural History Museum, London

If there's been a murder, it's not often the police that are first one the scene. MaggotsThere's something else which can arrive in as quickly as 15 seconds. Insects, which collect around bodies can provide vital clues, which is why entomologists, scientists who study insects, like Dr Martin Hall are often called in to help with forensic investigations. Georgia Mills visited Martin, at the Natural History Museum in London, to find out about one of the oldest forensic sciences...

Martin - Forensic entomology has got quite a long history.  There are even reports from 13th century China about insects being used to help solve crimes but really things started to get underway in the UK in 1935 when there was a famous case of Buck Ruxton who murdered his wife and his wife's maid, dismembered their bodies and threw them into a ravine, and when the body parts were found, many of them contained magots. And we've actually got in our museum collection some of the magots here.  They don't look very impressive - small brown things - they obviously weren't preserved very well.

Georgia - These are the magots from the actual case?

Martin - Yes, that's right,  yes - these are the actual ones, so from 1935.  They were identified as a blue bottle fly and have the lovely name Calliphora vicina. It's actually the most common Blue bottle on bodies in the UK. So back in 1935, the scientists aged these maggots and that aging fitted in with a witness who was knocked off his bicycle. He managed to write down the number plate of this car and it happened to be Buck Ruxton's car. It was him basically making a quick getaway from the scene where he dumped the body parts and it helped steer the investigation in the right timeline.  But it was the first time that magot evidence was used in the investigation. He was actually found guilty, Buck Ruxton, and hanged for those murders the next year in 1936 in Strangeways Prison, Manchester.

Georgia - It's incredible to look at these tiny shrivelled things in this jar. It's amazing to think they actually had an impact in a forensic investigation.

Martin - Absolutely, yes. Blow fly adults, they respond to the odours of decomposition amazingly finely and they have antennae on the head which act like the nose basically.  And I've got a sheet of sticky paper over here, you can see when I pull back the top here...

Georgia - Oh - it's full of flies...

Martin - It's covered in flies.  These are mostly Green bottle flies, actually. These were caught in Hungary and this sticky sheet was just place over a rat in an experiment and all of these flies have come in to land on this dead rat.

Georgia - There are hundreds...

Martin - Yes, exactly.  So they can detect the odours of decomposition really early and they'll arrive very soon after death. In our experimental works here in the museum, we use pig heads because they're cheap and easy to come by and sometimes, when we unwrap them up in the tower which is eight floors up, we'll have Blowflies arriving within 15 - 30 seconds.

Gerogia - Not only was I treated to a sticky tape full of flies, but Martin also had prepared a glass box of, very much alive, maggots, some of them had already started developing hard cases as pupae, but most of them were squirming along very unpleasantly.

Martin - So these maggots we've got in front of us are squirming around yes, but doing it rather lazily to be quite honest because it's a bit cold in this cocoon in the museum here. And what I've done is I've just taken out a few here on the side and you can these are all pupae, so they look a bit like a rugby ball. And they change in colour from a white one through sort of yellowy-orange to this dark brown and that colour transformation takes place over about eight hours or so.

Georgia - The size of the maggots found, along with the distinct colour changes of any pupae, can give scientists a very good idea of how long a body has been dead for...

Martin - What we do basically at a crime scene is collect the insects. They may be eggs, they may be larvae, they may be actually pupae.  Because, as I say, they wonder away from the body it's essential that at a crime scene we don't just collect the larvae on the body but collect those that have moved away. So we have to dig in the soil around the body and so forth, look under furniture if the bodies indoors and we then age these larvae or pupae in relation to the temperatures at the crime scene.

We actually employ that in a public event we have here called Crime Scene Live.  Members of the public come along on a Friday evening and join us in investigating a mock crime and we're actually able to use some of our latest cutting edge techniques here - CT scanning.  CT scanners are bits of apparatus that you commonly see in a hospital for looking inside your body and we can do exactly the same thing actually with much better resolution.  But we present these pictures to the public and we give them examples of pupae that were collected at a crime scene, and they have to try and work out how old the pupae are, and we think we can get to the resolution of about 10% of the age of these insects.

Georgia - Mmmm. Telling you about how long a bodies been there, that sounds like it can be quite important in the police establishing their timeline?

Martin - Yes, exactly, yes.  I mean, I've worked on about 170 cases with the UK police force now, and I've worked out about ¾ of them the major police question is "how long has this body been dead for?"  But there are other things that could be informative from insects. I mean, insects are ubiquitous in our environment so they're commonly encountered at a crime scene, Like all animals, you are what you eat, and these insects are obviously feeding on a dead body and they can actually ingest the substances in and on that body.

So, for example, they can ingest drugs that a person may have died of an overdose for example. The larvae can actually be collected and ground up and you can find the drugs in them. That might sound a bit ridiculous to say if you've got a body there, but sometimes there might not be a body there and we've worked on cases where a load of fly puparia were found. But the police were suspicious, and the pupae were ground up and inside them they detected drugs.  They then looked for human DNA, and they got a 75% match with a missing known drug user and, with that evidence, they were able to secure a conviction for the murderer. He'd disposed of the body but he'd forgotten to dispose of the insects that were feeding on the body.

Georgia - Ahh some nasty stuff goes on, doesn't it?

Martin - Yes, it's incredible actually.  I never expected to do anything like this with my entomological training and it certainly opens my eyes to a part of human activity and nature that I just didn't imagine.

09:14 - Your phone knows where you've been

New technology is changing the way we catch crooks, and phones are key in a lot of cases...

Your phone knows where you've been
with Jason Coyne, IT-group

Something that has come up a lot recently in trials is using mobile phones to place Radio towersuspects at the scene of a crime. This is called cell siting, which uses the call data record from your phone company, and can provide important evidence for the defence or prosecution. To find out how your phone can tell tales, Georgia Mills spoke to Jason Coyne, an expert in digital forensics at IT-group...

Jason - Typically, when expert evidence is presented by the Crown, the defense team will generally call experts, such as ourselves, to look at any digital forensics and ask us to interpret that evidence for them. Often, it's a case of validating the evidence that's been provided but, also, quite often we find that mistakes have been made.

Georgia - Something that has become a lot more important recently in trials, is using mobile phones to place people at the scene of a crime. This is called CELL SITING, and it uses the call data record from your phone company.  But, apparently, the picture is not always as clear as the prosecution would make it seem. So let's start - I'm getting a call from my friend, how does their voice reach me, and how does that notify the phone company to my location?

Jason - When your mobile phone is switch on and on the cellular network, it will negotiate which particular cell site or cell tower is best able to communicate your voice across the network to your friend.  So, once it's connected to a particular cell site, the mobile network will actually register which cell site your mobile phone was on when a particular call event takes place. And they use that so they can a) root the call through to you successfully but also for the purposes for billing, and it's that cell site record that can be used to try and identify where you were geographically positioned at any point in time in history.

Georgia - So these towers, they're just dotted across the country?

Jason - They are.  In the countryside, they look similar to big pylons with radio aerials on top but then, in the more urban areas, they're often positioned on businesses and you'll see a metal structure and then a series of aerials positioned around it. Typically, they have three aerials.

Georgia - How is this kind of information used by law enforcement?

Jason - What you will often find when you look through some of the papers that the police will provide as part of a court case, is you will see the instruction that they provided to the cell site analyst.  What will often be the case is that the police are trying to put a suspect in a particular location. One that I'm looking at at the moment is where the suggestion is that a particular suspect was inside a shop at a particular point in the evening. And the instructions to the cell site analyst was to test whether the suspect was in the shop based on his call data record. So, what happens in that scenario, is the cell site analyst will go to that particular location in the shop, he will switch on his cell site measuring device, and he will see if he was connected to that particular cell site. If his device tells him that he would be connected to that cell site, then what often goes in the police report, is that the suspect was inside the building at that point in time.

Georgia - So, is it as simple as that? Put you at the scene of a crime - case solved!

Jason - It's not.  It's not! Because the area that that cell site covers may well be 2/3/4, often 10 kilometers squared. So what you then need to do is after identifying that the suspect could well be in the shop, you've then really got to widen the circle and do what I call a 'range survey' to identify what other possible areas the suspect could have been.

Georgia - And this is something you've looked into for this case?

Jason - This is absolutely something that I've looked into for this case, and what we've found is that the suspect provided an alibi that he was actually at his girlfriend's house at the time that the robbery took place, and his girlfriend's house was about a kilometer away. But what I was able to do was I was able to cell site the retail shop and then go all the way from that shop to the girlfriend's house and, actually, at the girlfriend's house it was exactly the same cell site coverage. So, had he made a call from his girlfriend's house, the call data record would have been identical.

Georgia - I see. So at first glance this looked incriminating but, if you take a step back, it actually just supports his alibi?

Jason - Absolutely, yes. You've got to test both the positive case where you're trying to put the suspect, but really you've also got to consider what the possible range might be of that and look at the alibi cases as well, if you're going to test it properly.

Georgia - Do you think we'll see a trend in the future that this might get any more accurate?

Jason - Absolutely!  I mean, with the early generation 2G mobile phones, the cell towers would typically cover 15 kilometers and it was very difficult to position anyone. With 3G, the cell sites come down to covering, typically, about 2 kilometers. The 4G cell sites that are built really for carrying a lot of data, we're finding less range still and, you'll find that in some high streets, there's quite a high saturation of 4G cell sites every few hundred meters. So, it could well be the case that if you have somebody that's conducting a telephone call and that telephone call is handled by three or four different cell sites, then you can probably position that suspect with some degree of precision as they walk down that street.

Georgia - This kind of technology is leaving a big stamp on the justice system. The Hatton Garden raid has been noted as the BIGGEST robbery in British History after a group of men nicked about 14million pounds worth of jewellery. The gang even studied forensics in a bid to avoid leaving a trail but forgot about this new technology, they'd all had their phones on them. And cell siting isn't the only way your phone might tell tales on you...

Jason - A lot of work that we do now is actually on looking at the methods of communication between suspects because we find that often now, when crime is committed, people will take photographs and those photographs have a geolocation. So they are able to locate where the individual was when the photograph was taken and then, as these are exchanged through social media and things like that, there's quite a trail that can be examined.

Georgia - Wow! That sounds incredibly stupid to take a photo like a selfie in front of a robbery?

Jason - Yes, absolutely. We certainly see that. We often see that with crimes where people have stolen currency. So people, it would seem, like to have their photograph taken with large wads of cash in their hands.

Georgia - Jason Coyne, from ITgroup there.

17:26 - The tell-tale hum!

Wiretaps and CCTV can be important in police investigations, so how do you know what you've got is genuine?

The tell-tale hum!
with Peter French, J&P French Associates, York University

Audio can be key to cracking a case, be it wiretap evidence or identifying a suspect by Ultrasoundtheir speech. Peter French is from JP French Associates, and they provide expert assistance with forensic audio, as he explained to Georgia Mills.

Peter - The making of audio recordings is a very significant source of evidence in both criminal investigations and in prosecutions in the sense that if the police have reason to believe that someone is involved in criminal activity, they may record that person.

Georgia - That's Peter French, Chairman of speech and acoustics laboratory JP French associates. They do what's called audio forensics - not something I've ever heard of before, so he took me through some of the things the company does...

Peter - So one of the things we're asked to do is to compare the voices in criminal recordings to the voices of known suspects. Now when I say criminal recordings, they could be a whole range of things. For instance, if the police think that you're involved in high level crime - what they often refer to as top drawer crime they will, in fact, bug your premises under a warrant and we'd be comparing those voices with the voices of known suspects, usually from police interview recordings.

Georgia - What happens if the quality of the recording isn't too good?

Peter - This is, in fact, a very frequent scenario. A lot of the recordings that we get into the lab for processing have a lot of background noise in them or other problems of intelligibility associated with then. What we can do in those cases is to apply digital sound processing programmes to the recordings in order to reduce the noise. Typical scenarios would be things like undercover police officers posing as drug buyers, striking up deals with a drug dealer. This might take place in somewhere like a pub, so what we'd have in the background is a loud jukebox, we might have glasses clinking and what we'd be trying to do is to reduce the level of that noise relative to the foreground conversation so that it can be more clearly heard. And there's a variety of digital processing techniques that we use in order to enhance the sound quality.

Georgia - How does it actually work when you need to get something out? I'm thinking of CSI when they just click 'enhance' and the image becomes, clearer, and clearer, and clearer. What do you actually do - how does it work?

Peter - Well not the way that CSI portray it. In fact, CSI is one of our worst enemies because it give police officers and other clients very elevated expectations of what they're going to get back from us. The techniques we use - a whole range of them really. If it's broad spectrum noise (noise that goes right across the frequency spectrum), what we'll do is to use a technique known as spectral subtraction. This involves taking the recording and locating parts of the recording where there's no speech from the people in question - pauses between words and between sentences. And what we do is we sample that noise using the computer and then, once it's assembled a profile of the noise, it will remove noise with that profile from the sound file as a whole and that will, usually, improve intelligibility. 

Georgia - We had a clip of Peter working his magic on a real wiretap recording, however we, ironically, couldn't get legal clearance to broadcast it. However, the techniques actually sound very familiar to what we do at the Naked Scientists when we've got a poor quality recording - so I can give you a slightly less swish example. Here's a bit of audio from  SeaLife in London with a lot of background noise.

And here it is post noise-reduction - the editing software simply strips out anything that matches the background hum, leaving the speech. But just as you can edit the background noise out of a clip equally, if you were so inclined, you could chop up someone's speech just like a jigsaw and change the order or even the meaning of what they say. It's not something we'd ever do, but how do you know what you're getting is genuine?

Peter - We have available a new technique which is known as ENF analysis (Electrical Network Frequency analysis). We're talking here about a fact that we've got an alternating electric current in use, and the nominal rate of alternation in the current is 50 times a second, in other words 50 hertt but, in reality, it's never absolutely spot on 50 hertz. It alternates unpredictably 49 point something, 51 point something, 50 point something, backwards and forwards, and this happens on a moment to moment basis in response to different levels of demand on the electrical network. The point is though that because we get these moment by moment fluctuations in the level of alternation, that means that any slice of time on a recording where this mains hum is represented, actually tells us when that recording was made.

So let's say someone submits a recording to us and says this is a whole recording, it's continuous, which took place on the 4th April. Because we record the mains hum 24/7, we'll run it against a database and we'll say well, actually, the first 10 seconds of that recording were made on the 27th March, 2014. There's then 30 seconds of speech which comes from, let's say, the 31st October, 2014 beginning at 2 o'clock in the afternoon, and so on and so forth. So, by looking at the mains hum on a recording, we can usually tell a) when it was made and b) if it's a mosaic of pieces of recording from different times and dates.

What I should say is, in order to do this, the recording device doesn't necessarily have to be connected to the mains. Even if it's a battery operated device or even a mobile phone, as long as you're recording in say an urban environment or you're reasonably near to a mains source, you will often get inducted mains hum down on the noise floor of the recording and what we can do is to amplify it and analyse it from there - run it against the database.

Georgia - And is the hum different enough from day to day?

Peter - It's different enough from second to second. I mean, it's changing in frequency all the time and it's doing so totally unpredictably. It's not just that we can pin it down to a day, we can pin it down to the second that it was started and the second it was finished. It's almost like a fingerprint - a time fingerprint which is peculiar to to any section of time that we have on the recording and it will be unique to that slice of time.

25:03 - How does DNA profiling work?

DNA is seen as the gold standard in forensic science, but is it really all it's cracked up to be?

How does DNA profiling work?
with Dr Mari Uchimoto, Anglia Ruskin University

DNA evidence is seen as the gold standard in forensic science, often being used to clear DNAor condemn suspects, but what makes this type of evidence so important, and is it really infallible? Georgia Mills went to visit Dr Mari Uchimoto in her DNA lab at Anglia Ruskin University... 

Mari - The DNA that you get a crime scene is probably not going to be the cleanest sample. It might be off the floor, it might be off the toilet floor so, one of the first steps what we have to do is extract and purify it.  Also, to get rid of any contaminants that might be present, as well as cellular material. The second step would be to find out how much there is, so it's called quantification. The amount of sample that your normally have at a crime scene is usually very limited in both quality and quantity, so it's necessary to amplify that so. So, basically, get more of that and many, many copies.

Georgia - Mari amplifies the DNA with what is called PCR. DNA is double stranded - so imagine a train track. And when you heat the DNA, the train tracks split apart, and then, using some proteins called primers, this can rebuild each side of the split track, meaning you now have two train tracks! This is repeated over and over until you have billions of pieces of this original strand of DNA!

Mari - Once we've done that we can actually separate it and find out what fragments we actually have. So we use a  what's called a capillary electrophoresis machine and that can generate a DNA profile, and hopefully that's a full DNA profile.

Georgia - This machine in the lab looked a bit like a computer from the 90s, big grey and blockish, the front opened up to reveal several tiny glass tubes, which all  led into a small black box with a sign saying "Danger - avoid direct exposure to beam". So, the next stage is to take your DNA strands, which have been dyed a colour, and feed them into the machine...

Okay. So we're turning on the  - what's it called again?

Mari - It's called a - this model is a 3130. It's a genetic analyser and it's also used to separate fragments for DNA to produce a DNA profile, but it's also used for things like sequencing as well. So, it has a couple of different applications.

Georgia - It draws up the samples through all these tubes in a little labyrinth, puts it through this laser, which we've been warned very helpfully not to expose ourselves to, and then this laser if it detects the colours that have already been dyed, it will know here is the presence, or absence of a specific part of the gene?

Mari - Yes, yes, correct. And then, eventually, that will just pass through into the waste and then the information from the laser will then be transferred onto a data collection software where we can actually view the profile.

Georgia - Mari showed me one of the  DNA profiles they made - this isn't your entire genetic sequence - it's a set of, in this case, 17 sections of your barcode which are likely to be different in unrelated individuals. To my untrained eye it looked like a graph with small coloured spikes and these profiles from the crime-scene DNA can be compared to the profiles of the suspect's DNA - either incriminating or exonerating them. And the chances of a match with a stranger? About 1 in a billion. So, unless you have a particularly criminal identical twin, not bad odds.

Mari - Very, very accurate. Chances of having someone not being a match - 1 in a billion, so I think that's highly discriminatory. It's also very sensitive - you only need about 0.01 nanograms per microlitre. We can get a lot of data from that.

Georgia - Is there not a risk when every human has their own set of DNA that it could get quite easily contaminated?

Mari - Yes. Because the technique - DNA profiling- has become so sensitive that is always a constant worry. So, in the lab, we often wear lab coats; we completely clean down the surfaces; we generally have what are called pre-PCR and post-PCR labs,  just to make sure that we minimise the contamination, and obviously wear gloves, all the protective gear, tie your hair back, everything that you can think of.

Georgia - Dr Mari Uchimoto there.

Mari assured me that any accidental contaminations can be sorted out relatively easily - our prisons aren't full of genetic analysts. But, if  DNA can be so easily transferred, can the same be said for other types of forensic evidence, especially as technology advances means we're getting so much better at detection?

30:02 - Caught red handed: who shot the gun?

Contamination is just one of the problems faced by forensic science, which can lead to getting the wrong person.

Caught red handed: who shot the gun?
with James French, University College London

Forensic science is improving, but does this mean we're more likely to catch the rightGun crook? While we are getting better at detecting clues, this doesn't mean we're any better at interpreting them, which could lead to a miscarriage of justice. James French is from University College London's Centre for Forensic Sciences, and he spoke to Georgia Mills about why there's a problem with our understanding of the field...

James - There are a number of issues that have arisen in recent years in forensic science. It's been highlighted that, in a number of fields of forensic science, there's a lack of underpinning research to underpin our opinions and conclusions. This was captured in the report by the National Academy of Sciences in the US in 2009. I mean they really criticised forensic science as having a lack of scientific basis in a number of different areas and, I guess, the work that we try to do at the Centre tries to correct that to some extent and to improve the scientific basis for drawing conclusions in forensic science.

Georgia - But surely all of our technology is getting better so our conclusions should be getting better too?

James - I think this is actually one of the problems. We've come on so far in different areas of analysis and forensic science but there are still many unanswered questions and gaps in our knowledge in terms of interpretation. So, while we were able to answer the sort of "what" questions with greater certainty, the sort of "how" and "how did it get there" and "how long has it been there," they're still questions we need to engage in more research in order to understand.

Georgia - So what specifically do you work on?

James - I've conducted some research into looking at gunshot residue. Gunshot residues are produced when a firearm is discharged. They're made up of different compounds from the bullet itself and under high temperature and pressure, these particles are formed, they cool and condense as they are ejected from the firearm, and they're deposited in the vicinity. We might look to recover them at the scene of an incident involving a firearm and they can provide useful intelligence and evidence in the investigation of crime. By analysing the gunshot residues we might be able to determine something about the ammunition that was used, but also the presence of material on a suspect might indicate that they've been involved in the incident. So it could be highly valuable information. But, as I mentioned before, there are a number of gaps in our understanding when it comes to gunshot residues.

Georgia - We've got a demo here. We didn't get hold of a real gun, I'm sure you'll be glad to hear, but I've brought a toy gun that's used for shooting flies...

James - Okay.

Georgia - So, can you show me what would happen in terms of how the gun would leave residue on your hands and how you might go about finding it?

James - So, I'll use a little bit of artistic licence here. So we can imagine that this is just a handgun.  So, if I was to hold it like I'm showing you now, which is basically holding it in my right hand while supporting with my left hand and I was to fire the gun, the gunshot residues would be part of the blast cloud that was ejected at the front of the gun but also a little ejection ports in the side. This would form the cloud of residues that you see in a slow-mo picture of a firearm discharged and, typically, that cloud would be propelled back towards the shooter and in the vicinity.  And residues we would expect to be deposited on the hands, particularly on the back of the hands of the shooter, also on their face and hair, as well as their arms and sleeves but also around and into the environment surround the firearm. So, if I was to discharge the firearm as shown...

Georgia - Got for it...

James - Okay. We would expect to recover gunshot residues, potentially, from the back of my hand that was used to fire the gun. So, I'm going to sort of seed my hands with some fake gunshot residue, which is just a UV powder. I'm putting it particularly on the area that we would expect to locate it in and that's really between the thumb and index finger and in the gaps between my fingers there. And we can just see that actually that reflects under UV light...

Georgia - Shining blue thumb now.

James - Blue, purple. So when it came to sampling, imagine I was a suspect  and I've been apprehended, I might be sampled for gunshot residues, and the way of doing this is really quite simple. We just use a little sticky self-adhesive tab that's attached to a stub and these are sealed in a sealed tube that ensures that there can be no contamination from the environment. And the process is simply that with gloved hands, we would look to dab on the back of the hands, particularly focusing on the sort of webbing between the thumb and index finger to ensure that any residues were collected. Also in the cracks between fingers and knuckles as well to ensure that we were collecting the maximum amount of material. And that would be quite standard procedure after a firearm is discharged.

Georgia - Meaning you would be caught red, or in our case shining purple, handed - with evidence that a gun was fired in your hands. But does detecting this residue really mean it was you who dunnit? Part two of our demo suggested not...

James - So, if I was to shake your hand in the normal way and then we can look at your hand using the UV light, you can see that there's some reflecting between your thumb and forefinger there.

Georgia - Yes. I see, I've been contaminated!

James - Yes, and potentially implicated in a crime. You've also got some there that I can see with the naked eye as well. So there's a transfer that's occurred there and we've just demonstrated the principle of secondary transfer and it's been shown that this is applicable to a number of different types of evidence, including gunshot residue and other traces, but also DNA as well.

Georgia - It's not just fun with toys, James and his team have tested this effect with a proper controlled experiment. They got police to fire real guns, and then to shake hands with people who hadn't been present at the firing range.

James - The results of those experiments were that we found that gunshot residues could be transferred in fairly significant quantities from person to person. We actually found that the shooter was able to transfer material to another person who was then able to transfer to a third individual. Material was also transferred through the handling of a fired firearm as well. It's really just an extension of one of the basic principles of forensic science which is Edmon Lochard's axiom that every contact leaves a trace. And the aim of this research was not really just to demonstrate that this kind of thing can occur. But it was to inform forensic scientists who encounter gunshot residue about the possibility of the evidence that they're observing having arisen from a secondary transfer.

37:15 - The problem with witnesses

Forensic science is only crucial in about 3% of trials, so can we rely on eye-witness testimony?

The problem with witnesses
with Professor Graham Pike, Open University

Most trials rely heavily on eye witness testimony, however around 90% of wrongly Police Lineupconvicted people were put in prison by false testimony. So how much can we really rely on our memories, and are there any ways to make sure we don't lead our memories astray? Graihagh Jackson spoke to Graham Pike, professor of forensic cognition at the Open University, to first find out why we need witness testimony in the first place...

Graham - There was a case called "The Phantom of Heilbronn." This was a serial killer that German police and European police searched for for many, many years and believed to be the world's first transgender serial killer. This person was linked to murders, to robberies, to car crime, to thefts, so, was a very odd serial offender. But all the eyewitness testimony said that the person was a man but all the DNA evidence was from a woman, and rather than question the DNA analysis, the police believed this must be a transgender serial killer.

It turned out that a woman who worked in the factory that manufactured the tubes, or the swabs, or whatever they are, wasn't doing her job properly and contaminated every single device that she constructed, so it was her DNA that was being recovered from these crime scenes across Europe.  But, rather than question DNA analysis, the police invented the world's first transgender  serial killer who was roaming Europe committing all of these crimes.

Graihagh - Wow! That's quite a story.

Graham - Yes, I think that shows us that DNA analysis can be flawed but it also shows you that even the police, perhaps, can put a little bit too much store in forensic science. So, in reality, forensic science is not used in that many cases and is not this fantastic solution that never goes wrong

Really, if you want to know what actually took place in a crime, you need an eyewitness or the victim themselves to tell you what happened.

Graihagh - And this, I suppose, involves a lineup so walk me through what we happens when you catch the suspect?

Graham - Once they've got a suspect, one of the things they do is to show that person to the eyewitnesses and victims that were involved in the crime to see whether those people can recognise them. What we need is something like a lineup. We need the suspect themselves and people that look like them - we then need to show that to the witness. Now that means that the witness, the suspect, at least eight people that look like them, legal representation, as well as police and personnel, all have to be together in the same place at the same time.

Graihagh - A logistical nightmare that can, actually, delay this process by up to six weeks. And, I suppose, we all know that it's much harder to remember something from six weeks ago than it was yesterday but, that's not just all. Stress can really affect your memory too.  Picture this - you were held at gunpoint during a robbery. Imagine how stressful that is in the first place. Now you have to go in, confront them, identify them in the flesh.

Georgia - Absolutely the last thing I would want to be doing; but, isn't some stress quite good for your memory?

Graihagh - Yes, you're absolutely right. A little bit of stress, perhaps before your exam, can be really good for your cognition but lots of stress - not good at all!

Graham - But a lot of stress, such as a victim of a crime might experience, has a very deleterious effect indeed on cognitive performance.

Graihagh - Does that mean there's lots of mistaken identities and, in effect wrongful convictions?  And, if so how many?

Graham - Working out the incidence of miscarriages of justice is very difficult indeed because, of course, you need to know what happened in the original crime. If a very long, drawn out investigation and court trial wasn't able to establish that, then how is a researcher going to? Researchers looking at this estimate that something in the order of a quarter to a third of all identifications made by an eyewitness are identifying somebody who is innocent. Now that, of course, doesn't mean that person then goes onto be convicted. There are checks and balances,  there's the court procedure as well. 

In the United States, there's an organisation called the Innocence Project that investigate cold cases from many years ago in which physical samples were kept, but DNA analysis wasn't used in the original investigation. So far, they've overturned more than 300 cases of wrongful conviction. Some of those people were on death row. The average sentence served by those people was more than 13 years.

Graihagh - I mean, that seems very high and the fact that they were on death row frightens the pants off of me.

Graham - It's a very scary statistic. I would place a great deal of money indeed, that at least one person has been executed in the US who was innocent of the crime they committed. It could be many more. But it's undoubtedly the case that many people have served significant decades of their life in prison for crimes they didn't commit.

Graihagh - I mean that estimation alone makes me think something needs to be done. So, in an ideal situation, when it comes to eyewitness testimony, at least, we need a solution that gets rid of logistical nightmare stuff making it quick so that witnesses have a better chance of identifying a suspect and that's also stress free. Plus, the lineup needs to be conducted by an officer who doesn't know the identity of the suspect.

Graham - That's because the person can give off quite subtle non-verbal communication that cues the witness into who it is.

Graihagh - And then witnesses having identified someone often report looking at the officer to see if they got it right. Cue the non-verbal cue.

Georgia - Oh I see. Sounds like there's lots to think about her?

Graihagh - Yes but it turns out the solution is pretty simple... A database with hundreds of videos of people...

Graham - Rather than a police officer wandering around the local shopping mall trying to find eight people that look like the suspect, we can look through thousands and thousands of faces. That means that the people who appear in the parade will look more like the suspect and the parade will be fairer. Another significant advantage is video identification parade systems are perceived by witnesses as being less stressful.

Graihagh - This video identification parade - it sounds like it overcomes a lot of those problems but, I wonder, can we ever really be sure what we thought we saw.

Graham - I don't think it's possible to imagine a technology that could be developed, no matter how sophisticated, that could ever overcome the fundamental problems with human cognition. We kind of have this perception that when we're seeing something, we see everything that goes on around us, the world is exactly as we see it, and that we remember it almost like a video tape. Our memories are not like a memory of a computer. We interpret the world around us to make sense of it and so we remember things according to who we are and the expectations we have about how certain situations should play out. So, technology can assist in limiting those errors, but technology will never be able to overcome the fundamental frailty of human cognition.

Georgia - Hold on - that sounds like it's quite dramatically unreliable then and I know Graihagh mentioned earlier that forensic science can lead you on this complete wild goose chase. But the figures he said earlier about all those wrongful convictions are quite shocking to me and it sounds like DNA is actually what cleared their names in the end, but now he's saying that an eyewitness might be remembering something completely differently to what happened.

Graihagh - Yes, it's a really phenomenally, complex series of processors and I think every single tool in your kit is going to have it's positives and it's negatives and I think, ultimately, you've got to use as many of those tools as possible so that you get rid of some of those blind spots. Like when you're in a car, you've got three mirrors - your two wing mirrors and your...

Georgia - Is it rear view mirror?

Graihagh - The rear view mirror - yep. And you feel like you've got enough field of vision to drive safely but you've still got a blind spot.  I think that's the point Graham's trying to make. Use as many bits of kit as you possibly can to make it as fair as possible but, also, that there are blind spots and mistakes.

Georgia - I guess we just have to be aware that our brains aren't quite as clever as we thought they were.

Graihagh - Yes. I mean I think people often think, myself included, my eyes are like cameras and my brain is like this computer and everything I see is the truth, basically.  But, actually, our pictures have filters and when you're stressed the brain can do all sorts of funny things to those pictures.  So yeah, the brain is just phenomenally complex and we're only just really starting to understand some of the most basic, fundamental functions of the brain, yet alone some of the more really complex things we've been talking about today like stress, memory, and forgetting.

Brain scan

45:54 - Blame it on your brain

As neuroscience improves, does this mean defendants could blame their crimes on specific defects in their brain?

Blame it on your brain
with Dr Kyle Trieber, University of Cambridge

Our improved insight into the brain has been used in a couple of cases to argue that the Brain Scandefendant is not to blame for their actions: the defence argued that it was a disease, or tumour, inside of the their brain which caused them to commit crimes. But should this be the future of our courtrooms? Connie Orbach spoke to Dr Kyle Trieber, lecturer in neurocriminiology from the University of Cambridge to find out... 

Kyle - It's becoming more common to see neuroscientific evidence used in the courts. In the UK, there's a lot more restriction on it's use at the moment. In other countries that we see, there's evidence being used on a much more regular basis. There isn't a very clear protocol for how to use this material and that's something that law is dealing with at the moment. But, I come from the neuroscience side, and one thing that I see when I am crossing over into the legal area is that there's a very different kind of language being spoken. So, neuroscientist are speaking a scientific language, we're looking to find out what the truth is and we want to understand what is actually the processes that are underlying a particular behaviour. When you're looking at the legal side of it, you're trying to have two sides of the story, specify whether or not this person is responsible for the action or whether they should be held responsible, and it's a very different kind of approach. I think there's going to be a discussion that's going to have to be had between the sciences and the law side to better understand how we're going to integrate these two bodies of knowledge, which both have a great deal to bring to the table but to actually move forward for how we can use this information and how we can make it accessible to a court.

Connie - If someone were to say to me - "oh, there is a difference in their brain structure."  It's very easy to go - "okay, well that sounds like a good excuse."

Kyle - Yes, there's a lot of interesting research about the fact that if you show someone an image of the brain and they have damage to the brain, then that is very influential on how they think about that person, and that person's capabilities, and that person's responsibility for the criminal action, and the role that that damage would play.

Connie - So, clearly neural evidence or blaming it on the brain is a powerful defence but, maybe, the way it is used in court as 'evidence' for or against criminal behaviour, is pretty far from the more nuaunced information that a scientist sees. So, is there ever a circumstance where Kyle would be happy to say, there that abnormality is the reason for the crime?

Kyle - When you have these very extreme case, very colourful cases where, for example, you have a very rare kind of tumour situation - it's a very extreme kind of case. Most offending behaviour that we have there seems to be no real link to any kind of specific disability or specific brain damage or injury of any sort. So, it is a direction that we certainly need to be aware of because individuals will have certain vulnerabilities. But one things I always stop to think about in these kind of cases is, if there was an individual who has exactly these same cognitive abilities, are there individuals like that who aren't offending, who aren't committing crime? And, in the vast majority of cases we can find examples where that is the case, and that suggest to us that this is not the cause of their offending. That's not to say that it isn't playing a role in their offending, but it also isn't determining that offending. It doesn't make make it absolutely that offending is absolutely going to happen.

One of the things that a neuroscientist would like to communicate to people is that we're still learning a lot.  We don't actually have a very good range of knowledge as to what is normal. So, what are the variations we see in brains? Normally people's brain structures will vary, people's brain functioning will vary. To what extent does that actually lead them to behave in different ways? I don't think, at the moment, we have enough of an understanding of that to be clear to say, "if you have this particular brain structure or this functional abnormality, this is the result you're going to get as far as behaviour."

Connie - Similar to genetics in the nature/nurture debate,  the brain is just part of the bigger picture, and two people may have the same defect but one will not offend.

Kyle - This is one of the things we really emphasise a lot is the difference between the content and the machinery. So, you have the neurocognitive machinery and this will be based on both the brain and how it developed, and how it functions, but there's also experiential, so that depends on what your experiences have been on top. Over time, we know that people's experiences actually influence the structure of the brain as they're developing.

So, there's the machinery aspect of it and that will have an impact on how people perceive their environment, how they interact to them, the emotions that they experience but, there's also the content element.  The content is what they learn and what they gather from their environments and, in some ways, there's evidence, I would think, that suggests that that content may be more important than the machinery. Of course, the content is where we're going to have the most ability to influence individuals because we can change that information that they're receiving.

Connie - The content is clearly important, and in Kyle's own research she's finding out just how important by following teenagers over years of their lives and studying all of their interactions, and the places they go to see who offends and who doesn't.

But I'm still interested by these big tumours. The colourful one's as I'll put it. Because surely, how much we can blame these is only down to whether or not we can see them. A few decades ago, cognitive impairment wasn't a defence because we didn't know someone was impaired. As our technology continues to improve and we can see every little deviation from the norm, is is not possible that the brain as a defence becomes, if anything, more available?

Kyle - This is the exciting bit of neuroscience and neurotechnology at the moment.  It is expanding very rapidly. It's not only becoming more affordable but also there are many new technologies. So, one of the new things that has come out more recently is looking at the connections between areas of the brain and how messages and signals are sent between areas of the brain. We couldn't see that before and that, actually, is proving to be very important for understanding functioning, being connected to types of functioning that are often mentioned in criminological literature like "psychopathy," and other kinds of social behaviour because we can now see that that functionality, and we can see the structures that are there because of new types of imaging that we have.

It's a whole new area that we can look at for understanding the brain and how it works, and the fact that it is very interconnected. It may not be about having this structure or that structure that's functioning independently, but how they function codependently. And that technology, we would presume, is going to continue to get better and then we will better understand the structure and the function of the brain. But, the more we learn about the functionality of the brain, the more we understand and find that it is very much about interactions, and that we have evolved to interact with our environments and so we are looking for content. We need the content for the brain to develop; we need the content for the brain to function.  This is very new field in criminology because criminology has tended to look at the individual or at the environment and now we're trying to integrate the two. And it's about the person when they're in the environment and the action that then results.


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