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Photo of Dr Penny Haddrill

Ask Penny

Please post your questions for this week in the comments section below. Please ‘like’ questions posted by other learners if you are also interested in having these answered.

First of all I’d like to extend a warm welcome to you all, and thank you for joining the Introduction to Forensic Science course. It’s great to see so many people from all across the world taking the course and getting involved with the discussions. Thank you for all of your great questions this week, and for all of the positive comments about how much you are enjoying the course. I wish that we had time to answer all of your questions but I’ve focused on those that were most popular and most closely related to my own area of knowledge, which is forensic biology, and in particular forensic genetics.

DNA Databases

There were a few questions that related to DNA databases and the sharing of information between investigators in different countries in the world, for example the questions from Lindsay Todd, Annika Werger and Linda Witherspoon. There are now more than 60 countries worldwide who operate national DNA databases, with many more countries working to establish them. A DNA profile consists of a series of codes that represent the genetic types that an individual carries at different regions in their genome. Different databases worldwide differ in terms of the number of regions that are analysed, and so this can cause challenges when trying to compare data between countries. The legislation surrounding when DNA samples can be taken and in what circumstances they can be stored, and for how long, also differs between countries. We will look in more detail at the different DNA databases around the world later in the course, and discuss the issues surrounding the retention of DNA profiles.

In the UK there are two DNA databases, the UK National DNA Database, which was the first in the world to be established, and the Scottish DNA Database. The Scottish DNA database contains all DNA profiles produced in accredited forensic laboratories in Scotland, and these are automatically uploaded to and searched against the UK National DNA Database. As Scotland and England/Wales have different legal systems, these databases are subject to different legislation, and until recently the regulations surrounding the retention of DNA profiles differed, as Michael Mabbott correctly pointed out. In Scotland, if someone is convicted of an offence then their DNA profile can be retained indefinitely, but if they are not convicted it must be deleted (except under some specific circumstances). In England and Wales, DNA profile and fingerprint information used to be kept indefinitely, until a ruling in 2008 by the European Court of Human Rights in relation to the case of S & Marper vs UK that the indefinite retention of innocent people’s DNA profiles breached the European Convention on Human Rights. In response to this, the Protection of Freedoms Act (2012) was passed in England and Wales, resulting in the deletion of over 1.7 million DNA profiles from the UK national database, and the destruction of 7.7 million DNA samples.

In terms of sharing DNA profile information more widely among countries, this is a subject of much debate, as a few of you highlighted in your questions, Many people have concerns about the sharing of DNA profile data between countries, for example due to the potentially sensitive information stored within an individual’s DNA profile, and the wide variation in scientific standards among different countries. Sharing of DNA data is not done automatically, but depends on legal agreements between different countries. For example, several EU member countries have signed bilateral agreements with the United States to share DNA profiling information. Countries who are members of INTERPOL are able to submit DNA profiles to the DNA Gateway, which automatically searches against DNA profiles contributed from 73 member states and returns a result within 15 minutes. Within the European Union, the sharing of DNA profiling information is also carried out through the Prüm Convention, a treaty signed in 2005 allowing EU member states to make direct searches of DNA profiles in national DNA databases of other EU member states. Currently, not all member states are signed up to this agreement, and the UK initially opted out of the treaty due to concerns over the increased chance of adventitious or false matches due to the unusually large size of the UK database. This is exacerbated by the fact that until recently there was only limited overlap between the UK and countries in Europe in terms of the regions of the genome that were tested. This meant that a search could be made under the Prüm Convention with data for only six regions (whereas at the time typically ten regions were tested in the UK), which makes the likelihood of a chance match much higher. The newly adopted DNA-17 system in England/Wales and DNA-24 system in Scotland means that there is now much greater overlap with DNA profiles produced in Europe, and so the chance of adventitious matches should be lower. As a result of this and various other developments, in December 2015 the UK parliament voted to join the Prüm Convention.

Future developments in forensic science

Another question that a few of you asked, including Edward Omaka, Sony Das, Jan Ozkurt and Grayham Bickley, was about what developments and breakthroughs are on the horizon for forensic science. Although many of the techniques and tests used in forensic science have improved over the years as a result of technology getting more sensitive, more efficient and cheaper, there actually haven’t been many huge breakthroughs since the development of DNA fingerprinting and then DNA profiling in the 1980s and 1990s. One reason for this is that it can be very costly and time-consuming to introduce new techniques into laboratories, and new methods also need to be validated and checked to determine their reliability and accuracy before they can be considered admissible as evidence in court. However, there is a small but active research community working in forensic science and developing some new and exciting technologies that will hopefully be implemented in operational forensic laboratories in the future.

One major focus of the research community is in developing portable forensic testing, so that scientists can quickly give answers to the police at the scene of a crime. There is research being done looking at the development of chemical sensors that can be used at crime scene to identify different types of biological material, such as DNA or body fluids. One recent development that is beginning to be implemented in casework is testing samples at crime scenes or in police custody suites to produce limited DNA profiles very quickly. For example the ParaDNA system developed by the company LGC can now generate limited DNA profile information in just 75 minutes, which gives police very useful information to work with early in an investigation.

Another very exciting development is the use of RNA testing in forensic science. RNA is a molecule similar to DNA but whereas your DNA is the same in almost every cell of your body, RNA differs between different cell types depending on their function. RNA profiling can be used to identify what kind of tissue is present in an unknown stain, for example blood, semen, saliva etc. This can be particularly useful when mixtures of body fluids are found, as commonly occurs in sexual offence cases. This type of testing has not been implemented in the UK, but is being used in casework in the Netherlands and Australia.

Finally, another very promising area of research is in developing more sophisticated tests on DNA that allow the investigator to determine some physical characteristics about the individual who left the sample. If a DNA sample is found at a crime scene and a profile is produced, without a suspect or a match on a DNA database there is very little that investigators can do with the DNA evidence. However, there is now quite a large body of research developing tests that allow more information to be extracted from the DNA sample to help investigators try to identify the donor. For example, by examining the genetic type that an individual carries at certain places in the genome it is possible to determine what eye colour and hair colour they are likely to have, and also what ethnic group they are likely to come from. It is also possible to estimate an individual’s age by looking at a type of chemical modification in their DNA, which changes as they get older. Some of these tests are now so good that they can estimate an individual’s age to within a few years. There is scope for a range of characteristics to be tested for in future, for example there is work being done using DNA testing to determine the face shape of the individual. This is a really fascinating area of research with the potential to have a huge impact on the investigation of crime.

Forensic science in the UK

Several people also asked about the state of the forensic field in the UK, and how the changes that have occurred over the last few years have affected the provision of forensic services. Alan Le Marinel, Viv Guthrie, Harry Nichol and Carmel Collins all specifically mentioned the Forensic Science Service and the impact of cuts in police budgets. The provision of forensic services is different all over the world, and in some countries such as the United States and South Africa, most crime scene investigators are serving police officers. In the UK, scientists are not police officers, but the way forensic science is provided varies across the country. In Scotland, provision is by the Scottish Police Authority Forensic Services, which is a government owned organisation with four laboratories in Glasgow, Edinburgh, Dundee and Aberdeen. The situation in England and Wales used to be similar, with the government owned Forensic Science Service providing services to police forces. In 2012 the UK government closed the FSS as a result of huge financial losses, and forensic services are now either provided by private companies or have been moved in-house in police forces. Along with substantial cuts to police budgets, this fragmentation of the market has led to concerns that scientific standards may be compromised.

With limited budgets police may not be able to request a full range of forensic tests in their investigations, meaning they might miss vital evidence. In addition, moving testing to in-house police laboratories puts added pressure on scientists to come up with results to secure convictions for the police. Experts in the field have increasingly been warning that the situation is likely to lead to miscarriages of justice, and that a new governmental strategy for forensic science is needed. Although some of the private labs have been behind some high profile successes in the last few years, there have also been problems. For example, the company LGC were behind the re-examination of forensic evidence in the Stephen Lawrence case, which led to the conviction of two of his killers, but they were also behind the arrest of an innocent man for rape. Adam Scott was arrested and held in custody for five months because a DNA profile that matched his profile was identified in a swab sample from a rape victim. It later transpired that Adam Scott’s genetic material had become mixed up with material connected with the rape case as a result of human error at LGC.

In March 2016, the UK Home Office published its much awaited Forensic Science Strategy and announced that it planned to establish a new Forensic Science Service to move back to a national approach to forensic science provision in the UK. The forensic science community are pushing for this approach to include giving statutory powers to the Forensic Science Regulator, who is responsible for ensuring that high standards are maintained across the market, to make sure providers are delivering quality and consistency of service. It remains to be seen how the provision of forensic service in the UK will change over the next few years. It has always been difficult to get jobs in the forensic field, as vacancies are relatively rare, particularly since the closure of the FSS; it is hoped that this may change if the government invests money in a new national forensic science service.

The role of dogs in forensic science

One question that particularly caught my eye (because I am a dog lover!) was a question about the use of dogs in forensic science, which both Blanche Smith and Richard Rupp raised. Dogs are used in many aspects of forensic science because they have incredibly sensitive senses of smell; their noses contain about 200 million olfactory cells, compared to 20 million in humans. As a result, dogs can be trained to sniff out a variety of different substances, such as illicit drugs, explosives, and accelerants at the scene of a suspicious fire. In addition, dogs are often used to track and search for missing people or fugitives. One fascinating way in which dogs are used in criminal investigations is to detect the scent of decomposing flesh in order to find the bodies of deceased human beings. Cadaver dogs can locate human remains, and also determine where bodies or body parts may have been stored. Even if a body is buried underground or is underwater, a cadaver dog’s sense of smell is powerful enough to detect it. One really interesting example of a case in which cadaver dogs were used is the murder of Suzanne Pilley, a bookkeeper from Edinburgh who went missing in 2010 and whose body has never been found. Despite this, David Gilroy was convicted of the murder in 2012, with evidence being put forward by the prosecution that two cadaver dogs had identified several areas of interest in the office building where it is believed Gilroy carried out the murder, and in the back of his car. If anyone is interested in reading more about the involvement of the cadaver dogs in this case, you can read this article, and this Wikipedia page, and if you are interested in reading more about cadaver dogs in general, you can read this article.

Distinguishing between identical twins

Rachael Taylor also asked an interesting question about whether it would be possible to tell if someone killed their identical twin in order to fake their own death, and if there is any way to tell the difference between identical twins. Rachael rightly pointed out that any physical factors such as tattoos or piercings could be used, and it would also be possible to tell them apart by looking at their dental records, as they would not have cared for their teeth in exactly the same way could have differences in terms of cavities, fillings etc. Another method for distinguishing between identical twins is by looking at their fingerprints. Although our fingerprint patterns are partially controlled by our genes, the environment we develop in also determines how the patterns on our fingerprints turn out. Slight variations in conditions experienced by identical twins when they are in the womb means that even though identical twins may have similar fingerprints, there will still be enough differences in order to distinguish them. You will find out some more about this next week, when we will be looking at fingerprint evidence and how it relates to the case.

Until recently, one of the limitations of forensic DNA analysis was that it could not be used to tell identical twins apart. However, in 2014 a German company called Eurofins published a paper in which they sequenced the whole genome of a set of identical twins, as well as the child of one of the twins. Out of the three billion letters in the human genome, they were able to identify five genetic mutations that were present in the child and the twin who was his father. This has the potential to allow investigators to distinguish between identical twins in paternity cases, or criminal cases where one of a set of twins is the alleged source of DNA found at a crime scene. The study used a technique called next-generation sequencing, which is a method for very quickly and accurately sequencing a large amount of DNA. Although such methods are currently too expensive to be routinely implemented in forensic casework, the use of these new technologies looks set to revolutionise the way forensic DNA analysis is carried out in future.

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This article is from the free online course:

Introduction to Forensic Science

University of Strathclyde

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