Crime scene genes

It's CSI Naked Genetics, as we find out how genetic technology is used to solve crimes.
14 February 2018
Presented by Kat Arney
Production by Kat Arney.


Crime scene


‘Ello, ‘ello, ‘ello, what’s all this then? This month it’s CSI Naked Genetics, as we find out how genetic technology is used to solve crimes. Plus, we reveal the identity of the Phantom of Heilbronn - one of the most infamous characters in the recent history of forensic science - discover how DNA testing can free the innocent, and meet a giant Gene of the Month. 

In this episode

Hands covered in blood

01:10 - Genes at the scene

How is DNA evidence used to catch criminals?

Genes at the scene
with Eleanor Graham, Northumbria University

If you’re a fan of TV cop shows like CSI, you’ll know all about forensic genetics - using DNA to help police with their investigations. But how do they actually do it? And how much DNA do they really need? In search of clues, Kat Arney donned her deerstalker and headed up to Newcastle to meet researcher Eleanor Graham, a lecturer in forensic science at Northumbria University.

Eleanor - Traditionally, forensic DNA profiling has basically been focused on areas of the genome known as STRs which are little bits of the genome, repetitive bits of the genome showing loads of variation between different people so they can be used to tell two people apart.

Kat - This is kind of genetic finger printing when you see someone holding it up and there's all the bars and you're like, “yeah, yes, that’s you and that’s not you.”

Eleanor - That’s basically what it is, yes and the finger printing term is the term applied to the original technique developed in the ‘80s by Alec Jeffries in Leicester Uni and then it was taken and developed on to be more applicable to casework examples.

One of the most challenging aspect of forensic genetics is the actual samples you have to work with rather than the actual DNA work because the techniques we use in the lab, if you’ve got loads of good quality, high quality DNA you can pretty much look at anything you want to in a genome. But with forensic case work, you're working with really badly decomposed samples or burnt samples or miniscule ones that you can't even see with your eye. So all the techniques basically have to work with these challenging sample types and that’s where the interesting bits come into it, I think.

Kat - So addressing that challenge, so you’ve got a tiny speck of blood or a couple of pieces of hair, what are the sorts of things that you could do to try and get some genetic information out of that?

Eleanor - Well as I said, traditionally, the genetic information that we’ve been focusing on really tells us the difference between two people or we can do things like kinship analysis: who is related to the owner of that DNA sample?

We’re now moving into the realm of more what we call ‘phenotypic’ characteristics. So, we are now in an area where it’s possible to determine things about what people look like in terms of hair colour, eye colour, skin tones, some aspects of stature, facial characteristics. So we are in a realm that we can do that.

There's also markers that we can use to trace geographic ancestry, so you may be able to tell something about where someone’s from in the world. But it’s all still on a very statistical basis, not a 100 per cent.

Kat - And in terms of dealing with these samples, how do you amplify the DNA? How do you get enough DNA to actually study from a tiny speck of blood and what are the challenges and the risks with doing that?

Eleanor - The lab techniques that we use are the same all over the world – genetics, molecular biology. It’s all around the basic polymerase chain reaction at the moment. So, PCR technique, you choose which bits of DNA you want to look at, you design a system which will amplify up those specific bits of DNA. The challenges that we have with our sample types are the extreme sensitivity of the methods that we use.

These methods are capable of developing a profile from as little as a single cell or even less than a single cell. I'm talking about fragments of DNA that may be present on surfaces that have been touched or literally fragments that are in the atmosphere. These fragments, if they can get into our test tubes in the laboratory, they can actually show up in our results. That’s how sensitive these tests are.

That obviously opens up a can of worms for contamination issues associated with forensic testing which have been a problem in the past. Gross contamination issues tend to be picked up very easily, but the more tricky ones to deal with are what we call ‘sporadic’ or ‘random contamination events’ where literally, fragments from the atmosphere may appear in our test results and we have to determine whether it’s from our sample or from somewhere else.

Kat - This is something I've always wanted to know like, everyone who works at the forensic lab, do you have to get your DNA analysed and put in the database so you know that if you have accidentally contaminated something, you know it wasn’t you that did the crime? “I'm innocent, guv!”

Eleanor - Yeah. This is one of the quite interesting aspect of our student projects as well because we always say at the beginning, “If you make a mistake, don’t hide it because we’ll know it was you.” So yeah basically, everybody that works in a DNA lab will have their DNA profiles on an elimination database. This goes for also, people who work at crime scenes – police officers, laboratory workers, but also extends to personnel who actually manufacture the reagents and the consumables used for forensic DNA testing.

This goes back to a case quite a few years ago now. In Germany, it is known as the Phantom of Heilbronn case where the same female DNA profile was turning up in crime scenes all over the country, all over Germany, ranging from homicides to thefts - a wide range of different types of crime with the same perpetrator turning up in the DNA profiles.

Kat - A master criminal!

Eleanor - It seems so but it was a bit too strange to be true. So eventually, someone looked into the details of this and it turned out that the profiles were all turning up on the swabs from the same manufacturer. When they went to the manufacturers and asked could they sample of stuff, lo and behold, one of the females who produce the swabs was found to match the crime scene stains. So since then, it is so important that we have these elimination databases in place.

Kat - From watching crime dramas and things like that, most of us will have an idea that using forensic genetic analysis is something you do for human crimes, murders, sexual assaults, that kind of stuff. But obviously, animals have DNA and animals can be involved in crimes and trafficking. What are some of the ways we can use forensic DNA information to solve other non-human crimes?

Eleanor - That’s absolutely the case and we do teach that in our classes here at Northumbria that it’s not all about the human DNA. Animals all have the same patterns of DNA, the same features in their DNA, some of them are incredibly similar to us like the chimpanzee showing 97 per cent DNA the same as us.

So, we do use the same methodology to work on crimes and we can think about these crimes in different ways. The animal could be a victim in the case of poaching and trafficking of illegal species, and they can actually be used as weapons as well. So we’ve had cases where the DNA profile of a dog has been taken from a victim when the dog has been used as an attack animal.

We have them in all different scenarios and this also extends to non-animal sources. We can use plant DNA in exactly the same way, tracing things like the origin of cannabis leaves. So, have they all come from the same plant? Have they come from the same plantation? Where in the world are they coming from? So we can use DNA to establish that as well.

Kat - What about ancient crimes or even ancient people? What are the challenges with trying to use your forensic method there?

Eleanor - This is something that’s always interesting quite a lot. It’s the really challenging aspect of how you can actually get enough information from the really, really degraded, really difficult sample types. But the techniques to actually recover the DNA from the materials that are left have really come along now. Both the sensitivity of the methods themselves and the recovery of the actual – what’s left – have advanced to a stage where we can actually paint quite an interesting picture of people of the past.

We have done some work on skeletons that were found at Roman sites up in Northumbria near Hadrian’s Wall. We were able to answer some questions that the archaeologists had conflicting evidence about like the actual origins of the skeletons found in certain environments within a fort. It was thought by archaeologists that maybe the people were the Roman army that had come in. But our genetic test showed that they actually had more of a British origin so we were able to answer questions like that.

And even in some cases for ancient DNA, the sex of an individual might not be obvious from the remains that are found. If you don’t find the skull or the pelvis, it can be quite difficult to assign sex to an individual. We’ve been out to do that as well to be able to determine biologically based on the presence of X and Y chromosomes or just a Y chromosome whether or not a skeleton remains are male or female which can also be really fascinating depending on the circumstances.

Kat - Eleanor Graham, from Northumbria University.

Bloody handprint on window pane

10:06 - Who's who

Crime scenes are a mess of DNA, making it hard to spot the true criminal.

Who's who
with Georgina Meakin, University College London

Forensic scientists gather and analyse DNA from crime scenes to help the police identify criminals. But it’s rare that a sample will be completely pure - DNA traces from victims, perpetrators and others can all be mixed up together. So how do they separate out the genetic fingerprints of different people? To find out, Kat Arney spoke to Georgina Meakin - a lecturer in crime and forensic science at University College London who is researching this very problem.

Georgina - At a crime scene there's the obvious body fluids that you think about - you think about the blood, maybe like some pool of tissue like brain matter, or maybe semen if it’s a rape case. They're the obvious things that we can detect easily and you may even just be able to see by the naked eye.

But nowadays, because our DNA technology has advanced and has become so sensitive, we can now sample a surface that you can't actually see anything on, but you might expect to find DNA. So a surface that you might expect someone has had contact with. So let’s say it’s a burglary. It looks like someone has broken in through the window. You might sample the window sill, maybe some glass samples, and you might find DNA from the person who’s been in contact with that.

Kat - But presumably, that criminal is not the only person to have ever touched that window. So, how do you analyse the sample? How do you get information out and then figure out who might have been there?

Georgina - That’s a very, very good point. As I mentioned, from a crime scene perspective, you're thinking about where to target. You have to think about who might have touched it. Obviously, you're thinking about the offender touching. But other people may well have had contact with the item. You know, a residential building or a room, people have been living there, they’ve got to be depositing their DNA in a variety of ways.

But we also can transfer DNA indirectly. So for example, you can shake someone’s hand, you can transfer their DNA onto a surface that they’ve never touched. You can perhaps touch a surface someone else has touched and transfer their DNA that way. So, when we sample a crime scene, quite often, you're going to get DNA from more than one person.

So you're quite right. It starts getting complicated and that’s where the kind of research that I do and other scientists around the world are trying to generate the kind of date to help inform the way we decide when you get a mixed profile – DNA from several people – is there a way of looking at that and say, “Okay, this profile is coming from the person who’s touched it most recently” for example.

At the moment, I don’t think we’re there yet with the data. Perhaps that’s not completely widely held view. I'm certainly challenging the status quo on this method with the research that I'm doing.

Kat - Let’s drill a little bit more into how you're analysing this DNA. With my genetic hat on, I'm, “Ohh! It’s all about DNA sequencing” but that’s not necessarily what you're doing. What are the ways in which you would analyse DNA and does it depend on what sort of sample it is and how much you’ve got?

Georgina - All of those are valid points. The way we routinely analyse DNA, we use profiling rather than sequencing, so we’re genotyping.

Kat - This is the genetic fingerprint rather than looking at all the letters of the DNA, right?

Georgina - Exactly, that. So, what we do is we target a number of different areas on the different chromosomes. It used to be that we looked at 10 areas that was routinely done within the UK but now, different jurisdictions in the UK use different numbers. So for example in England and Wales, we use 16 areas plus an area that looks at the sex, so male or female. And we will prefer to these technologies as DNA-17, so we’re looking at 17 areas.

Kat - You’ve got a profile from some DNA from a crime scene and it could be a bit mixed up. There could be several people in there. How do you then start trying to deconvolute that and work out whose DNA might be whose?

Georgina - So there's a number of ways of doing it. Firstly, you might know that someone’s DNA is definitely there. So for example, you’ve taken a sample from a victim, you expect to see their DNA present so you can essentially subtract their DNA and you get the unknown DNA that you then want to compare to someone else. Another way in which we do it is by looking at the respective proportions of the different DNA.

Kat - I always have this image of a forensic scientist from the telly, from the CSI where they're holding up this kind of gel or an x-ray with loads and loads of bands on. They’re like, “Yes! That’s the genetic fingerprint. That’s the killer.” Does it still look like that?

Georgina - No.

Kat - What does it look like now? You spoiled my dreams! What does it look like now?

Georgina - So literally, it looks like a series of peaks. So when we analyse the DNA, we essentially get what looks like a graph so we can look at the heights of the peaks that are present. The higher the peaks, the more DNA you have present. So it might be that all the peaks belonging to one profile are much higher, therefore you have more DNA from the other peaks so you can separate out a profile in that way.

Ultimately, if you can't do either of those things then it gets really difficult and then it kind of becomes out of the remit of a DNA analyst and more into the remit of a statistician. And there are a number of different statistical algorithms, programmes, probabilistic genotyping software that’s now available which it can assess the probability of matches between crime scene profiles and people of interest.

Kat - From your perspective and the research that you're doing, where are we going next? What are you excited about and what do you think will be kind of the next big thing or the big questions that people are really starting to get their teeth into?

Georgina - So in terms of applying DNA analysis to forensic science, we’re very good at getting a DNA profile. We can get DNA profiles in very, very small amounts of DNA, just a few cells. We’re getting better with the statistical analysis and being able to attribute that DNA to someone. So now the real question are less about who is it and how did it get there.

So when we find DNA at a crime scene, we want to know, is it coming from the person involved in the crime or was it already there, or did it get there through innocent means? This is the kind of research that I think is really critical and the forensic science regulator has raised this in her last few annual reports that we really need research to start assessing the transfer and persistence of trace evidence of which DNA is one.

Kat - That is kind of scary actually because we all walk through the world just shedding our DNA – you know, our skin, tissue, hair or saliva – all these things and that it could completely innocently end up being in some forensic examination. It’s quite scary.

Georgina - It is scary and there are documented cases where we’re seen it actually happened where someone has been accused of a crime that they didn’t commit because their DNA has been indirectly transferred to the crime scene. The question is, can we tell from the DNA that we recover from a scene, how it got there, and we really need more experimental data to be able to assess that or at least try and assess the probability of different explanations being the case.

Kat - What are the kind of ways that people are thinking of to approach this problem of how did this DNA get there? Is it just a trace that’s got there by accident?

Georgina - So essentially, what we want to do is when you're assessing that finding of DNA, you’ve got what the prosecution said happened and you’ve got what the defence say happened. And you want to try and see, can you distinguish between those two scenarios?

So we need data to be able to input into a statistical model to assess which version of event is more likely and that’s where the kind of research that universities and some forensic science providers are doing to try and generate that empirical data. So we’re looking at things like when you wear an item of clothing and someone else wears it, what DNA do you expect to find? Are you going to get more DNA from the first wearer or the second wearer?

Currently, research I'm doing is suggesting that actually, it tends to depend on the person because some people deposit more DNA than others. But these are the kind of questions we need to be investigating and generating data for.

Kat - Georgina Meakin from UCL.

The window of a prison cell

18:17 - Guilty until proven innocent

DNA evidence can free the innocent as well as convicting the guilty

Guilty until proven innocent
with Carole McCartney, Northumbria University

Forensic genetic evidence can be used to help police put guilty people behind bars, but it can also be used to prove that a convicted criminal is actually innocent. But, as Kat Arney discovered, it’s not just about big-name famous efforts like the US Innocence Project, which has used DNA to exonerate more than 350 people of crimes they didn’t commit. Carole McCartney, a reader in law at Northumbria University, is particularly interested in making sure DNA evidence is used from the very beginning to protect the innocent as well as prosecute the guilty...

Carole - One of the things that we also know about DNA is that if you use it at the beginning of an investigation, it can ensure that innocent people don’t get convicted. Often, that is forgotten because the attention is taken by getting innocent people out of prison. Well it would be quite good if we didn’t put them there in the first place and I think DNA has played a very important role in preventing wrongful convictions as well as very important role in exonerating people who’ve been wrongfully convicted.

Kat - So the kinds of people that have been released under the innocent project and the sort of work that you’ve been involved in, tell me about those. What are the sorts of cases that get taken up to say, “Actually, we don’t think this person did it and we think we can prove it.”

Carole - One of the difficulties of course for the people who are in prison is that forensic evidence is really only collected in the more serious crimes. So your murder, your rape, sexual violence is where you're going to find forensic evidence and to find that it’s been retained as well is important.

So of course, those people who have been convicted of lesser crimes, non-violent crimes and so forth, DNA very rarely plays a role in those sorts of investigations. So if you’ve been wrongfully convicted of that, DNA is not going to save you.

Kat - So if you haven't done your tax return, there's no forensic DNA going to get you out there.

Carole - I mean, for domestic violence, if you beat your wife, of course, the DNA is not going to save you there because DNA is going to be on your wife anyway and so forth. So, it’s only very small amount of crimes for a start that DNA is ever going to come to your rescue.

And you'll find that it can come to the rescue most often where lots of unreliable evidence has been used to convict somebody and we know now unreliable evidence to be things like eyewitness identifications, forced confessions we know so much more about now. But also importantly, other forensic science, even other DNA science that has been used to convict people that we can now subsequently go back and say, “Well, that wasn’t valid. That wasn’t reliable. That wasn’t robust.”

So things like bite analysis, hair analysis, but even the earlier versions of genetic science that we’ve come on so much more, the science has developed so much more now that we can perhaps determine that people didn’t contribute to a DNA profile now that we couldn’t have done before and so forth. So DNA can correct the mistakes of forensic science in the past but also other unreliable forms of evidence as well.

Kat - So, if you're trying to prove someone’s innocence, so you need the forensic data from the crime scene and you need a sample from them, how do you then go about kind of getting them back into the system to get someone to look at this again?

Carole - Well, it’s very difficult. I mean in the UK, it’s particularly difficult and we even have a body that’s been established to look at alleged miscarriages of justice. So, if you lose your appeals, you can go to the CCRC – the Criminal Cases Review Commission - and try and get them to re-investigate things. And if they think there's a potential for forensic evidence to be able to assist in determining whether this was a miscarriage of justice or not then they might be able to undertake that testing.

One of the critical problems there though that we found over the years is there's no requirement, no legal requirement for them to keep this evidence. So if you're convicted, lose your appeals and so forth, why are the police going to hang on to their evidence? And of course, when we had the forensic science service, the forensic service would keep it all in a nice store cupboard and labelled and everything. But they don’t exist anymore. So now, 43 police forces decide, do we bother keeping this? And very often of course, they decide not to. So, it’s very, very difficult.

Kat - That sounds like a significant justice issue if evidence is being destroyed but might later lead to someone having their conviction overturned.

Carole - Yeah, it is!

Kat - It’s bad!

Carole - It is very bad and I think it’s going to get worse before an awful lot more attention. There's a few people trying to draw attention to this as researchers working on this. There was the very big case of Kevin Nun where in Kevin Nun’s case, he wants some DNA testing done but he can't get the police to give him the evidence. And they’ve said, “Well actually, there's no requirement for the police to go and search for evidence when you’ve been convicted and you're in prison.”

The police don’t keep on investigating things, but of course, there's an individual in prison. How are you going to get the evidence or find the evidence? You can't so you have to call upon the police and the police don’t have to do it so you end up with an impasse.

Kat - What are some of the most interesting cases that you’ve come across that have been solved or have been resolved through the use of DNA to exonerate someone?

Carole - DNA very often is about identification so it’s, was it person A or was it person B? And DNA is very useful obviously in being able to say, “Well, it was person A’s DNA, not person B’s.” The difficulty with cases is, that doesn’t often tell you then, did they commit a crime? It just tells you that that was their DNA.

So, we have cases where people’s DNA has been found in supposed crime scenes. But it doesn’t tell you how their DNA got there or what they were doing when their DNA was found or when they put their DNA there. And I think increasingly, we’re going to have appeals on this basis.

We all know for example the taxi driver who had a very severe skin complain to the point where his friends called him “Flaky”. It was not hidden that this taxi driver had a skin complain. But there were victims who had particles of his skin found on him and of course, he then got accused of being involved in these crimes relating to these different victims. Until a solicitor can come along and say, “Well actually, they’ve all been in his taxi.”

It doesn’t sound very savoury but obviously, they’ve been in his taxi and picked up particles from his skin there. So, it’s not always about all the DNA science can tell you who it was. Yeah, but can they tell you what they were doing or how that DNA got there? Appeals are going to be based on this very difficult question that geneticists can't answer.

Kat - What are the biggest risks of using genetic information to convict someone? Is it, there might be an extra match in the database to someone that’s not you or is it this risk of contamination, or just sort of randomly picking up someone’s DNA from their flaky skin?

Carole - I think the science is developed enough. It’s fairly safe and secure now that if you put a full profile or a sample of somebody’s blood into a DNA database, chances of you getting an adventitious match with somebody that isn’t you is very, very slim. So that’s quite easy to pick up.

But contamination at crime scenes is not easy to pick up. So for instance, you know, we’re in this room now. We will probably leave something behind like I don’t have a skin disease but I will still leave behind traces of my skin and so forth that probably, if a crime were to be committed in this room later this afternoon, we would be in the frame. So we would need to be able to explain that we were here before the crime was committed but of course, you can't put a time on the DNA. So, that’s always going to be an issue.

Kat - And one of the other concerns is the ethical issue. I've talked to my podcast before about the ethics of people having their DNA sequenced for some health reasons or personal interest or ancestry, it being stored by companies kept in big databases. How secure is that? What are people doing with it? How much information do they need to know? Do those sort of arguments apply to the data that’s gathered for forensic purposes?

Carole - Well, very much so because it’s the state that are in charge of it and I think anytime the state are gathering information off citizens, there has to be a justification for that. I mean, I've talked to people before and they say to me, “Why don’t you want your DNA on a DNA database?” And I've said, “That’s not the question. The question is, why do you need it? And if you don’t need it, I don’t have to give it to you.”

Kat - If you haven't done anything wrong, what's the problem with giving your DNA?

Carole - If I haven't done anything wrong, well why do you need my DNA? That’s what the answer should be, not, “I haven't done anything wrong. You can have it.” “I haven't done anything wrong. You don’t need it.” Literally you will solve no crimes – I hope – by having my DNA in a DNA database, unless we do do something in this room.

Kat - A bit of light murdering!

Carole - Yeah. But literally, I have committed no crimes. I don’t plan on committing any. Why do you need my DNA? It just makes your DNA database more complicated, unwieldy, bigger, expensive, slower. It’s no point in having it. And that goes for most of the population. I mean, when we started the DNA database, the idea always was to have the active criminal population on the database. The problem with that is we don’t know who they are to just say, “Could we just put your DNA on the database?” So there's always going to be an element of people being caught up in the DNA database.

Of course, what we saw in this country is we’ve got so over enthusiastic that we put nearly every Tom, Dick and Harry on the DNA database until it got taken to the European Court of Human Rights. And they said, “No. This does not make for upholding people’s human rights to privacy and so forth.” If they're innocent, they don’t need their DNA on the DNA database. There has to be a justification for keeping people’s DNA. So we’ve rolled back now.

But whether we’ve rolled back enough, that’s still a debate to be had and of course, it’s always still incremental if you're not keeping an eye on things then. And it’s not just whose DNA ends up on the DNA database and whether we’ve drawn the line in the right place there. I don’t believe we have but others believe we do.

If we do have the line in the right place, it’s also then, what they can do with their information when they’ve got so it’s, “How can it be used for research? Do they use it for familial searching?” So, someone’s partial DNA comes up, they run it through the database to see who’s close to it and then can start tracing family members and so forth which is a legitimate crime investigation tool in its place, but also has very serious ethical issues around whose DNA is on that database and what they're doing with that information.

Kat - Carole McCartney, from Northumbria University - and in case you’re wondering, no we didn’t go on a killing spree afterwards, honest...

A giant

29:25 - Gene of the Month - Fezzik

A fruit fly gene named after a gentle giant.

Gene of the Month - Fezzik

Our gene of the month is Fezzik - the name of the giant in the book and film The Princess Bride - which has been given to a fruit fly gene formerly known as CG9509. It comes from a new research paper by two scientists in Germany - Amanda Glaser-Schmitt and John Parsch - who were investigating the role of a control switch in the DNA near the gene. They were finding out how small changes in the DNA sequence of the switch found in various populations of flies around the world affected the activity of the gene, whose function was previously unknown.

The researchers discovered that the gene normally acts to keep a lid on growth, and variations in the genetic control switch lead to subtle differences in body size in different populations. In fact, embryos and adult flies completely lacking CG9509 are unusually large - hence renaming it after the gentle giant Fezzik. Although the name hasn’t yet been officially adopted by the scientific community as it was only coined in January this year, we’re sure the researchers hope that their new name will make a big impact.

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