DNA Evidence – Can it be wrong

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DNA Evidence – Can it be wrong

The history of DNA and its uses in law enforcement

DNA profiling (also called DNA fingerprinting, DNA testing, or DNA typing was developed in the early 1980’s and is the process of determining an individuals DNA characteristics called a DNA Profile. It is now the most commonly used forensic technique in criminal investigations in trying to identify an individual.


99.9% of human DNA sequences are identical in every person, however enough of the DNA is different enabling it to be possible to distinguish one from the other, unless they are identical twins who share the same DNA profile. A DNA profile can be obtained from various substances such as blood, sweat, flakes of skin, urine and semen.

What is and who invented DNA?

DNA wasn’t invented, it has always been there, it is an acronym for deoxyribonucleic acid which is a molecule that carries genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses.

The modern process of DNA profiling was developed in 1984 by Sir Alec Jeffreys while working at the Department of Genetics at the University of Leicester, along with Peter Gill and Dave Werrett of the Forensic Science Service.

When was DNA first used?

It is often said that DNA was used first to convict Colin Pitchfork of the murder of two school girls in the 1980’s. However it is actually right to say that before it did, it was actually used to exonerate an innocent suspect.

In November 1983 15 year old Lynda Mann was found raped and strangled on a deserted footpath in Narborough. A semen sample taken from her body revealed an offender with type A blood and an enzyme profile that matched only 10 percent of males. With no other leads the case would remained unsolved for almost 3 years. In July 1986 two days after she had been reported missing another 15 year old girl, Dawn Ashworth was found dead, she had also been raped and murdered. A 17 years old male named Richard Buckland was the prime suspect. He had been arrested and apparently during police questioning he admitted the crime and had knowledge of Ashworth’s body. However Mr Buckland suffered with learning disabilities and DNA profiling later showed that those confessions could not have been true.

Jeffreys was responsible for developing all of the DNA extraction techniques and demonstrating that it was possible to obtain DNA profiles from old stains. The biggest achievement in cases of this nature was the development of the preferential extraction method to separate sperm from vaginal cells. Using that technique Jeffreys compared semen samples from both victims and showed that they matched, both girls had been the victims of the same man and that man was not Buckland. The police undertook a voluntary mass screening of 5000 males in Leicestershire but the offender was still not caught.

The case would remain cold until 12 months after the discovery of Ashworths body when a woman contacted the police regarding a conversation which she had heard in a local pub. She informed them that Pichfork had paid another man £200 to provide a DNA sample for him. Pitchfork was arrested, admitted both offences and was sentenced to life imprisonment.

DNA now


Ever since the case above DNA has been widely used in criminal prosecutions around the globe.

It is always thought of as bombproof or watertight; imagine sitting on a jury and being told;

“The offender was a white man in his early thirties with brown hair, the offence was committed in London. The defendant denies having any contact with the victim. A DNA profile of an individual was found on the victim, that profile matches the defendant. The chances of that profile not being that of the defendant are 1 in 1 billion; the defendant is in his early thirties, lives in London and has brown hair”

Would you find him not guilty? I’d suggest probably not, but what if we removed the DNA evidence and you were left pondering how many males are there in London, in their early thirties with brown hair? It makes a huge difference, you might think.

Can DNA evidence be wrong?

DNA is powerful evidence, but can it be wrong? Well it appears that it is has been shown to have been misinterpreted in a string of cases. It is reported that research published by Ruth Morgan, director of the Centre for the Forensic Sciences at University College London suggests that rulings in 218 successful appeal cases between 2010 & 2016 argued that DNA evidence was misleading.

How can DNA evidence be misleading?


Advances in techniques in DNA extraction from samples recovered from victims or crime scenes means that DNA profiles are now being obtained from microscopic traces of material and often lead to mixed DNA profiles being obtained. A mixed profile is that of two or more individuals which is often difficult to prise apart. If a mixed profile is recovered from piece of clothing for example, will the major profile be from the last person to have worn in, somebody who has previously worn it, or somebody who has just touched it?


Morgan’s studies revealed that whether DNA is left or not can be influenced by things like, how long it was after somebody washed their hands or which hand a person touched and object with, but more importantly, it revealed that some people simply leave more DNA than others. Tests showed that the DNA of the person that they were looking for left either a partial or non viable profile, yet DNA from another person, who had not been in the lab had been recovered, proving that DNA could be transferred innocently.

In many cases where a DNA profile is obtained, it cannot be established what substance the trace came from, was it skin cells, saliva, blood or some other bodily fluid? Nor can it be determined when the DNA was deposited.

Research into the Rotherham abuse scandal revealed that DNA from semen could be recovered from clothing which had been washed over a period of several months. What was also discovered is that suspects DNA was also recovered on other items that had never had any bodily fluid on them meaning that the washing machine was actually contaminating other items of clothing.

DNA in the future

DNA evidence is certainly here to stay, the BBC reported only yesterday that a new DNA forensic laboratory was to be set up in Nottinghamshire, meaning that DNA results will now be obtained in hours rather than days and its use is clearly on the increase in police investigations. Advances in science may mean that the evidence may become even more reliable as far identification is concerned, and advances in technology may mean that the process can be made much quicker, but what is most crucial is how it is interpreted. It is about juries having explained to them what the results mean, how they might have been contaminated or easily explained and not simply baffling them with huge odds.

How you can help

What is also required is further research and Ruth Morgan wants to do just that by building a research lab in order to try to stop miscarriages of justice in the future; “We can tell you what something is, when we find it, but we can’t tell you what it means. The interpretation of evidence is absolutely critical if we don’t do that research, and we don’t answer those questions, then evidence is going to be going into court that isn’t interpreted correctly”.

She has taken to Crowd Funding to try to raise £1 million to get a research lab up and running and they are well on their way to achieve their goal, so far raising £200,000 towards their target.

Incentives are promised to backers: those who pledge £500,000 could have the lab named after them, while £10,000 backers would have a private dinner with the UCL forensic scientists on the team. For a mere £40 donation you will receive a limited edition piece of giclee microscopic artwork and donating £25 would prompt an invite to a live forensics seminar in London. You can donate to this valuable cause here.

How we can help

If you are accused of a crime involving DNA evidence it is vital that you secure the services of solicitors who have experience in analysing DNA results, having the knowledge and expertise to interpret them correctly, study the techniques used and investigate areas where contamination might have occurred. Experienced lawyers know exactly what to examine, what to challenge and how to challenge it.

Jonathan Wall – Burton Copeland Solicitors

Jonathan has over 25 years experience in dealing with all levels of criminal offences and defending clients in the most complex and serious cases. To contact Jonathan click here or to read more about him see his profile.


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