I’m sure I’m not the only one who watched ITV’s recent 2 part dramatisation ‘The Code of a Killer’. The programme was based on the first criminal case to use the newly discovered DNA fingerprinting techniques. Who would have thought during that initial, ground breaking case that DNA would become such a huge part in criminal investigations today.
Although DNA had been discovered in the 19th century, it was in the 1940’s that scientists discovered that DNA contained the code for life. In 1984 Alec Jeffreys discovered DNA fingerprinting. DNA Fingerprints can be found in our blood, hair follicles, bone, saliva, skin, semen and sweat. The fingerprint is made up from DNA we inherit from our parents and make every one of us unique. There is a 1 in 64 billion chance that two unrelated individuals would have comparable (that is similar but not identical) DNA.
In 1985 the DNA fingerprinting technique was used for the first time in an immigration case, and in a paternity case. Although in its infancy, Alec Jeffreys was approached by the Leicestershire police in 1986 to help with a criminal investigation.
In 1983 15 year Lynda Mann was raped and murdered, and then in 1986 15 year old Dawn Ashworth was also found raped and murdered in a nearby location. When they arrested and interviewed a 17 year old local boy, he confessed to killing Dawn, but not Lynda. Detective Chief Superintendent David Baker believed that both crimes had been committed by the same man – both crimes appeared to be very similar, and tests on the semen revealed they were the same blood group. Why would someone choose to confess to 1 murder but not another?
DCI Baker asked Jeffreys if his fingerprint technology could confirm if their suspect had killed both girls, using a blood sample they had collected to compare against evidence collected from both crime scenes. The results showed that their suspect had not (despite his confession) killed either girl, but did prove that 1 man was responsible for both crimes.
With little other evidence to go on, the first mass DNA screening was introduced. Around 5000 local men had their DNA taken in order to eliminate them from the investigation. In 1987 a woman overheard a conversation between Ian Kelly and some colleagues, stating that he had been paid to take the DNA test for a friend – this friend had apparently already taken the test for someone else who was worried the police would harass him for a previous conviction. Ian Kelly confirmed that he had taken the test for Colin Pitchfork. Pitchfork was arrested and his DNA confirmed as matching the crime scene samples. A conviction followed.
1987 Also saw the first conviction based on DNA evidence in America – Tommy Lee Andrews was convicted of rape.
Since this first case almost 30 years ago, DNA fingerprinting has become an invaluable tool in criminal investigations. What was once ground-breaking is now routine. As DNA testing has improved, allowing the analysis of smaller or older samples, several cases that had remained unsolved prior to 1986 have now been closed. But, DNA not only convicts the guilty, it has helped to free the innocent. Even in that original case in Leicestershire, the DNA evidence prevented an innocent boy being convicted. In America, over 300 people have been found innocent of the crimes for which they were convicted since 1989 (and 140 of the real perpetrators have been found).
The first case in the UK where DNA evidence was used to prove innocence after a conviction was Regina V Shirley. Michael Shirley was convicted for the 1987 rape and murder of Linda Cook. DNA fingerprinting was available by this time, but the semen sample collected could only yield a blood group. It was too small for profiling. By 1999 new techniques meant that smaller samples could now be analysed, but in this case the profile was inconclusive. The sample was mixed DNA, but could not be compared accurately without reference samples from both Shirley and Cook.
In 2001 these reference samples were obtained, and once each individual profile had been ‘removed’ the mixed DNA sample showed “an array of ‘foreign’ DNA bands which did not match either the victim or the appellate”. Combined with a review of original and witness testimony, Shirley’s conviction was quashed in 2003.
Of course DNA is not always straight forward. Someone who has received a blood or bone marrow transfusion will have two types of DNA, their own DNA remains unchanged in cells, but blood contains the donor’s DNA. In the case of blood transfusion this is temporary, but with bone marrow transplants it is permanent. In some instances people are even born with 2 different sets of DNA.
Medical advances are such that scientists now believe they can ‘edit’ our DNA, which could help to prevent or even erase certain diseases. How would this kind of alteration affect the efficacy of DNA fingerprint testing? Developments are still being made when it comes to DNA and forensics. Trials are being made with police forces using portable machines which can analyse swabs and compare them to national databases in less than 2 hours. Who knows, in a few years officers might carry portable DNA kits as standard issue.